Central Nervous System - Board Review Summary

PART I - BRAIN METASTASES: CNS-ACTIVE SYSTEMIC THERAPY, SRS, AND WHEN TO HOLD RT

Management Paradigm + Dose Anchors

Scenario	Default management frame	RT / dose anchor
Asymptomatic, small-volume disease with highly CNS-active drug option	Multidisciplinary deferral of RT can be reasonable when lesions are small, non-eloquent, non-hemorrhagic, minimally edematous, and close MRI follow-up is reliable.	If progression or symptoms develop, salvage with SRS/FSRS when feasible. Common intact-met anchor for <2 cm lesions is 20-24 Gy x 1.
Symptomatic, large, hemorrhagic, edematous, or eloquent metastasis	Prioritize local therapy. Surgery is favored when diagnosis, mass effect, hydrocephalus, or decompression matters; otherwise SRS/FSRS is typical.	<2 cm: 20-24 Gy x 1; larger/eloquent: consider 24-27 Gy / 3 or 30 Gy / 5 depending on OARs and V12/V20/V24.
Limited intact brain metastases	SRS alone is standard for 1-4 lesions. Level I evidence now supports SRS for selected patients with 5-20 lesions, and expert practice may treat even more when total volume, OAR geometry, performance status, systemic control, and MRI follow-up support it.	Use lesion size/volume rather than count alone; keep single-fraction brain V12 around ≤10 cc when feasible.
Resected metastasis	Postoperative cavity SRS/FSRS is preferred over WBRT for cognitive preservation and is better than observation for surgical-bed control. Preoperative SRS is an increasingly used and actively studied option in selected patients, while postoperative SRS/FSRS remains the board anchor.	Small cavity: single-fraction 12-20 Gy by cavity volume; larger/irregular/dural-risk cavities: 24-27 Gy / 3 or 30-32.5 Gy / 5.
Extensive brain metastases, not SRS-suitable, reasonable prognosis	Use HA-WBRT + memantine when hippocampal avoidance is oncologically safe.	Common WBRT regimen: 30 Gy / 10; hippocampi D100% ≤9 Gy, Dmax ≤16 Gy.
Poor prognosis / high treatment-burden brain metastases	Steroids, antiseizure therapy when indicated, supportive care, or short-course WBRT only if symptom palliation is likely and logistics are reasonable.	Short palliative WBRT anchor: 20 Gy / 5; QUARTZ-style data support avoiding reflex WBRT in poor-prognosis NSCLC patients.
Leptomeningeal / dural-predominant disease	Diffuse leptomeningeal disease is usually palliative and often WBRT- or CSI-based. Nodular or pachymeningeal/dural-predominant disease can sometimes be treated with focal SRS/FSRS for durable local palliation.	WBRT 30 Gy / 10; pCSI is individualized for selected solid-tumor LMD with good PS and controlled systemic disease.

When Drug-First Can Be Reasonable

Scenario	Key data	Practical takeaway
EGFR-mutant NSCLC, asymptomatic small-volume brain metastases	Osimertinib-based first-line therapy has strong CNS activity and is a reasonable drug-first strategy in carefully selected, asymptomatic patients.	Defer RT only with close MRI surveillance and low-risk lesion features; treat upfront if large, symptomatic, hemorrhagic, brainstem/eloquent, or causing edema.
ALK+ NSCLC, asymptomatic small-volume brain metastases	CROWN: lorlatinib produced high intracranial response and durable intracranial control.	Reasonable to defer RT initially in carefully selected asymptomatic patients with strong CNS-active targeted therapy options.
HER2+ breast cancer	HER2CLIMB supports intracranial activity of tucatinib-based therapy, but CNS response may be less dependable if tolerance is poor or dose reduction is needed.	Favor SRS when likelihood of durable drug response is low or systemic therapy cannot be maintained.

When Local Therapy Usually Stays Upfront

Scenario	Key data	Practical takeaway
Symptomatic melanoma brain metastases	CheckMate 204: symptomatic patients had median intracranial PFS only 1.2 months; Australian ABC randomized phase II reported intracranial response only 6% in symptomatic patients.	Upfront local therapy is recommended for symptomatic brain metastases even when CNS-active systemic therapy exists.
SCLC brain metastases	FIRE-SCLC found no OS detriment with SRS compared with WBRT in matched cohorts, but WBRT improved time to CNS progression.	WBRT remains a familiar board answer for extensive intracranial SCLC; SRS is increasingly used for limited-volume disease with close MRI follow-up.
Large, hemorrhagic, edematous, brainstem/eloquent, or symptomatic lesions	Most systemic-therapy deferral data are strongest in asymptomatic, small-volume, low-risk lesions.	Treat locally first or early. Surgery, SRS, or FSRS is chosen by size, mass effect, diagnosis need, OAR proximity, and systemic plan.

Board pearl: modern systemic therapy does not eliminate the need for local CNS therapy. The key distinction is symptomatic / eloquent / hemorrhagic / large / edematous disease versus small, asymptomatic, non-eloquent metastases in a patient starting a highly CNS-active regimen with reliable follow-up.

Standard of Care for Limited Brain Metastases

N0574 established SRS alone as the preferred approach over SRS + WBRT for limited brain metastases. In patients with 1-3 metastases, cognitive decline at 3 months occurred in 63% with SRS alone vs 92% with SRS + WBRT, with better QOL in the SRS arm and no OS difference.

Yamamoto / JLGK0901 is the classic prospective bridge from 1-4 lesions to multiple-met SRS: selected patients with 5-10 metastases had noninferior OS compared with 2-4 metastases after SRS alone.

Aizer JAMA 2026 extends level I evidence to selected patients with 5-20 brain metastases. SRS improved symptom burden and interference with daily function relative to HA-WBRT.

Practice nuance: lesion count is now a weaker gatekeeper than total tumor volume, lesion location, expected systemic control, patient logistics, and confidence in close MRI surveillance. Treating >20 lesions with SRS can be reasonable in expert practice when volume and dose spillage are favorable, but boards still expect you to name the stronger evidence base through 20 lesions.

Brain Met SRS Planning Pearls

MRI: ideally within 1 week, thin-slice 1 mm sequences.
PTV: 0-2 mm; many high-quality frame-based or frameless workflows use 0-1 mm, while 2 mm improves setup robustness at the cost of V12.
Single-fraction dose for lesions <2 cm: 20-24 Gy x 1.
RTOG 9005 size ladder: 24 Gy for ≤2 cm, 18 Gy for 2.1-3 cm, 15 Gy for 3.1-4 cm; larger lesions often move toward FSRS because local control worsens when the single-fraction prescription is reduced for volume/OAR safety.
Single-fraction brain V12: keep ≤10 cc.
Conformity index: <2.0, ideally around 1.0-1.2 depending on target complexity and platform.
Prognosis: use diagnosis-specific GPA / BrainMetGPA rather than lesion count alone; total intracranial tumor volume, often <15-30 cc in multi-met SRS series, is often more informative than count.

Radiosurgery Technical Principles

Concept	What to watch	Board / practice pearl
Coverage / prescription IDL	Prescription isodose coverage of GTV/PTV, maximum dose, hotspot location, and whether the prescription is to 50% vs 70-90% IDL.	Gamma Knife commonly prescribes near the 50% isodose line; linac SRS/SRT often uses higher IDLs. The same prescription dose can imply a different maximum dose, dose gradient, and intratumoral heterogeneity.
Conformity / selectivity	How much prescription dose spills outside the target.	Conformity is not enough by itself: a plan can be conformal but still have a poor gradient or excessive low-dose bath in multi-target SRS.
Gradient index	How quickly dose falls outside the prescription isodose.	Especially important for small brain mets, optic-adjacent lesions, and single-isocenter multitarget plans.
Normal brain dose	V12 for single fraction; V20/V24 for 3-5 fraction SRS; integral low-dose bath for many targets.	HyTEC brain and HyTEC optic are better references than memorized single numbers alone.
Platform and technique intent	Frame/mask immobilization, image guidance, shot/isocenter strategy, collimation, MLC/cone size, rotational arcs, prescription IDL, gradient, and end-to-end QA.	HyperArc-style linac SRS/SRT and a more homogeneous VMAT plan can both prescribe 25 Gy / 5, but they are not the same planning problem. HyperArc-style planning emphasizes conformality and rapid dose falloff; conventional VMAT often emphasizes homogeneous coverage across a margin-bearing target.
Gross target vs CTV-based target	Whether the target is a discrete gross lesion/cavity or a broader microscopic-risk CTV, and whether hotspots fall in tumor vs normal brain included by margin.	For CTV-based diseases such as glioblastoma, prescription IDL and hotspot control matter because a radiosurgery-style hotspot may sit in clinically normal brain encompassed by CTV margin. Match technique, IDL, and heterogeneity to the target biology rather than to fractionation alone.

Constraint source: AAPM TG-101 is the classic SBRT/SRS constraint table reference, but CNS SRS planning is increasingly shaped by HyTEC dose-volume tolerance papers and institutional platform-specific QA.

Emerging Addition After SRS

METIS: Tumor treating fields after SRS for NSCLC brain metastases prolonged time to intracranial progression without worsening QOL or cognition, but OS and broad routine-use questions remain unsettled. It is a new option to know, not a default board answer.

PART II - RESECTED METASTASES, RADIATION NECROSIS, AND WBRT

Postoperative SRS Is Preferred Over WBRT

N107C randomized patients with one resected metastasis and showed that postoperative SRS improved cognitive deterioration-free survival vs WBRT, with no OS difference. This is the key trial supporting cavity SRS after resection.

Mahajan et al. randomized completely resected 1-3 brain metastases to postoperative SRS vs observation. At 12 months, local recurrence-free rate was 72% vs 43%, confirming that postoperative SRS improves local control even after GTR.

Postoperative SRS Volume Design

Register pre-op MRI for reference.
GTV: entire resection cavity; include the adjacent surgical tract for deep lesions; exclude edema.
If there was pre-op dural involvement: consider a 5 mm dural margin beyond the pre-op tumor; this may push toward FSRS depending on cavity size, OARs, and dural extent.
CTV: 0-2 mm, excluding barriers like bone, air, falx, and tentorium.
PTV: optional symmetric 0-1 mm depending on immobilization, image guidance, and platform.
N107C single-fraction cavity ladder: 20 Gy if <4.2 mL, 18 Gy if 4.2-7.9 mL, 17 Gy if 8.0-14.3 mL, 15 Gy if 14.4-19.9 mL, 14 Gy if 20.0-29.9 mL, and 12 Gy if ≥30 mL, when single-fraction cavity SRS is selected.

Challenging Post-op Cavities

Scenario	Common regimen	Planning limit
Larger / irregular postoperative cavities	24-27 Gy / 3 fx	Brain + target V20Gy <20 cc
Very challenging cavities / fractionated cavity SRS	30-32.5 Gy / 5 fx	Brain + target V24Gy <20 cc

Radiation Necrosis: Diagnosis + Management

Issue	Board-review anchor
Diagnosis	No single SOC imaging test definitively distinguishes recurrence from treatment effect. Use serial MRI morphology, perfusion MRI, spectroscopy/diffusion when helpful, symptoms, steroid response, and surgical pathology when management depends on certainty.
Mild symptomatic RN	Boswellia 4200-4800 mg/day; vitamin E 1000 IU/day + pentoxifylline 800 mg/day; dexamethasone 4-8 mg/day.
Severe / steroid-refractory / progressive RN	Escalate to bevacizumab, LITT, or surgery depending on symptoms, mass effect, accessibility, and diagnostic certainty.

Whole Brain RT for Select Patients

NRG-CC001 supports HA-WBRT + memantine for patients with extensive brain metastases who are ineligible for SRS but have reasonable life expectancy. Common hippocampal constraints include D100% ≤9 Gy and Dmax ≤16 Gy.

Conventional WBRT still has a role when HA-WBRT is not feasible, especially with leptomeningeal disease or substantial tumor involving the hippocampal region. HA-WBRT is generally avoided when disease is in or very near the hippocampal avoidance region. Consider parotid sparing V20 <25% when feasible to reduce acute xerostomia.

PART III - HIGH-GRADE ADULT-TYPE DIFFUSE GLIOMA

Management Paradigm + Dose Anchors

Clinical setting	Default management frame	RT / dose anchor
Glioblastoma, IDH-wildtype; fit adult, usually <70 with KPS ≥60	Max safe resection or biopsy -> partial-brain RT with concurrent/adjuvant TMZ. Discuss tumor treating fields after chemoradiation for motivated patients who can manage device burden.	60 Gy / 30 fx with daily TMZ, then adjuvant TMZ.
Molecular glioblastoma / IDH-wildtype diffuse glioma with glioblastoma molecular features	Treat like glioblastoma, IDH-wildtype when a diffuse astrocytic glioma has TERT promoter mutation, EGFR amplification, or +7/-10 even without necrosis or microvascular proliferation.	Usually 60 Gy / 30 fx; target both enhancement/cavity and bulky non-enhancing disease.
Astrocytoma, IDH-mutant, grade 4	Do not call this glioblastoma in WHO 2021/2024 language. Treat as a high-grade IDH-mutant astrocytoma; CDKN2A/B homozygous deletion can define grade 4 even without necrosis or microvascular proliferation.	Usually 59.4-60 Gy with adjuvant alkylator strategy individualized by grade, prior therapy, and trial context.
Astrocytoma, IDH-mutant, grade 3	High-grade IDH-mutant astrocytoma. RT followed by adjuvant TMZ is the clean modern answer; concurrent TMZ contribution is less clear than adjuvant TMZ.	59.4 Gy / 33, then adjuvant TMZ.
Oligodendroglioma, IDH-mutant and 1p/19q-codeleted, grade 3	High-grade oligodendroglioma. RT followed by PCV is the classic evidence-based backbone; TMZ is often used when PCV tolerance is a concern while awaiting definitive CODEL interpretation.	59.4 Gy / 33, then PCV or TMZ depending on patient/trial context.
Older but fit patient	Hypofractionated RT + TMZ is the clean board answer. Selected robust older patients may still receive standard 6-week chemoradiation.	40.05 Gy / 15 fx + concurrent/adjuvant TMZ, especially if MGMT methylated.
Frail, poor PS, or RT-burden-sensitive patient	Short-course RT alone, TMZ alone if MGMT methylated and RT is impractical, or best supportive care depending on goals and symptoms.	25 Gy / 5 fx for elderly/frail patients with high treatment burden; 34 Gy / 10 or 40.05 Gy / 15 for intermediate fitness.
Recurrent disease	Clinical trial, re-resection, bevacizumab/systemic therapy, LITT, or re-irradiation depending on interval, volume, location, and prior dose.	Common re-RT anchors include 25-35 Gy / 5-10 fx; composite dose review is mandatory.

WHO 2021: Glioblastoma Is IDH-Wildtype

Molecular glioblastoma refers to IDH-wildtype glioma without classic histologic grade 4 features but with molecular hallmarks such as TERT promoter mutation, +7/-10 copy number pattern, or EGFR amplification. Treat these tumors like glioblastoma, IDH-wildtype for RT purposes, often to 60 Gy.

Do not call IDH-mutant grade 4 astrocytoma "glioblastoma" in WHO 2021 language. It is astrocytoma, IDH-mutant, grade 4. In IDH-mutant astrocytoma, CDKN2A/B homozygous deletion is a grade 4 molecular feature even without necrosis or microvascular proliferation.

High-Grade Glioma Planning Principles

Post-op MRI: obtain early, ideally within 24-48 hours; 72 hours is the usual outer window before postoperative enhancement/blood products make residual disease harder to interpret.
MRI timing: ideally within 2 weeks of planning; up to 3 weeks may still be usable.
Use both: T1 post-contrast and T2/FLAIR; always review the pre-op MRI.
GTV: cavity + residual enhancement + bulky non-enhancing disease.
CTV: GTV + 1-2 cm, anatomically constrained; RTOG vs EORTC style differs mainly in how explicitly edema/FLAIR is included.
Evidence note: no OS difference was found between larger historic RTOG-style vs smaller EORTC-style volumes.

Volume style	Concept	Practical note
RTOG-style two-phase	Initial volume includes cavity/residual enhancement plus T2/FLAIR abnormality with margin to about 46 Gy, then boost around cavity/enhancement to 60 Gy.	Classic board-friendly approach; anatomically trim at barriers and do not blindly chase all nonspecific FLAIR.
EORTC-style single-phase	Single target around cavity/residual enhancement with about 2 cm margin to 60 Gy; less explicit full-edema treatment.	Often smaller normal-brain volume; useful conceptual contrast with RTOG.
Limited-margin / adaptive practice	Selected centers use smaller, image-guided margins such as about 5 mm around high-risk disease in carefully chosen contexts.	This is a practice variation/trial-style nuance, not the default board answer for newly diagnosed glioblastoma.

Grade 3 IDH-Mutant Planning and Dose

Subtype	CTV margin	Dose	Post-RT systemic therapy
Grade 3 IDH-mutant astrocytoma	1-1.5 cm, anatomically constrained	59.4 Gy / 33	Adjuvant TMZ; concurrent TMZ contribution is less clear.
Grade 3 IDH-mutant, 1p/19q-codeleted oligodendroglioma	1 cm, anatomically constrained	59.4 Gy / 33	PCV is classic; TMZ is common when PCV tolerance is limiting.

Common Pitfalls

Planning MRI too old (≥4 weeks).
CTV not anatomically constrained.
Failure to cover expected pathways of spread.
Under-treatment of bulky non-enhancing disease.
Failure to inspect adjacent FLAIR and multifocal disease.
For supratentorial tumors, letting CTV drift below the tentorium or into cavernous sinus without direct disease extension.

Key Glioblastoma Trials

Stupp / EORTC-NCIC established 60 Gy / 30 with concurrent and adjuvant TMZ as the standard backbone for fit patients. MGMT promoter methylation is both prognostic and predictive for TMZ benefit.

Perry NEJM 2017 randomized patients age 65+ to hypofractionated RT alone vs RT + concurrent/adjuvant TMZ. Using 40.05 Gy / 15 fx, median OS improved with TMZ with similar QOL.

Roa 2004 supports 40 Gy / 15 as a shorter alternative to 60 Gy / 30 in older patients. Later short-course data support 25 Gy / 5 for selected elderly/frail patients when treatment burden is central.

EF-14 supports tumor treating fields with adjuvant TMZ after chemoradiation for selected, motivated glioblastoma patients without early progression; the practical limiting issue is device burden and scalp toxicity.

Glioblastoma escalation traps: routine dose escalation beyond 60 Gy, upfront SRS boost, brachytherapy boost, and bevacizumab added to upfront chemoradiation have not become standard OS-improving answers.

Grade 3 IDH-Mutant Evidence Hooks

CATNON supports adjuvant TMZ after RT for grade 3 IDH-mutant astrocytoma; the concurrent TMZ signal is less clear.

RTOG 9402 / EORTC 26951 support the long-term survival benefit of adding PCV to RT in 1p/19q-codeleted anaplastic oligodendroglial tumors.

PART IV - IDH-MUTANT GRADE 2 DIFFUSE GLIOMA

Management Paradigm + Dose Anchors

Entity / setting	Default management frame	RT / dose anchor
Grade 2 IDH-mutant, low-risk after maximal safe resection	Observation remains appropriate for favorable, asymptomatic, reliably followed patients. Vorasidenib is an option for selected residual/recurrent non-enhancing disease after surgery when delaying RT/chemo is desirable.	No immediate RT; if RT becomes indicated, common dose is 50.4-54 Gy by histology/risk.
High-risk grade 2 IDH-mutant glioma	High-risk features include age ≥40, STR/biopsy, neurologic symptoms, large/unfavorable location, or unreliable surveillance. RT followed by PCV is the OS-improving board standard from RTOG 9802.	50.4 Gy for oligodendroglioma; 54 Gy for astrocytoma; then PCV x6 when appropriate.

High-Risk Grade 2 LGG: Chemoradiation Standard

RTOG 9802 is the key board trial for high-risk low-grade glioma. Patients age ≥40 or with STR/biopsy received RT alone 54 Gy or RT followed by PCV x 6. Long-term follow-up showed a major OS benefit with chemoradiation, commonly cited as median OS about 13.3 vs 7.8 years.

EORTC 22845 supports observation after surgery for selected low-risk patients because early RT improves PFS and seizure control but not OS. The board nuance is that observation still requires close follow-up: even the RTOG 9802 low-risk cohort had substantial 5-year progression risk.

INDIGO established vorasidenib as an option for residual or recurrent non-enhancing IDH-mutant grade 2 glioma in carefully selected patients, delaying progression and next intervention. It did not compare against standard adjuvant RT/chemotherapy, and OS is immature, so it should not replace RTOG 9802-style treatment for clearly high-risk patients.

Who benefits from vorasidenib? A practical way to frame INDIGO is the patient with residual/recurrent, non-enhancing grade 2 IDH-mutant glioma where delaying RT/chemo is a meaningful goal. See this commentary-style review: Who will benefit from vorasidenib?

Planning and Dose for Grade 2 IDH-Mutant Glioma

Subtype	CTV margin	Dose	Post-RT systemic therapy
Grade 2 IDHm oligodendroglioma	1 cm	50.4 Gy (range 45-54 Gy)	PCV for high-risk patients when appropriate.
Grade 2 IDHm astrocytoma	1-1.5 cm	54 Gy (range 50-54 Gy)	PCV is classic for RTOG 9802 high-risk framework; TMZ often used when PCV tolerance is a concern.

LGG planning pearl: acquire high-resolution 3D T2/FLAIR and avoid excessive hot spots, generally keeping them <107-110%.

LGG treatment traps: dose escalation above about 50.4-54 Gy has not improved outcomes, and TMZ monotherapy is not generally favored over RT-based therapy for high-risk grade 2 glioma, especially IDH-mutant astrocytoma.

PART V - MENINGIOMA

Management Paradigm + Dose Anchors

Scenario	Default management frame	RT / dose anchor
Grade 1, asymptomatic/incidental	Observation with serial MRI is often preferred, especially for small convexity or skull-base lesions without growth or symptoms. Upfront treatment can still be reasonable in selected cases.	No RT unless growth, symptoms, patient preference, or difficult future salvage risk.
Grade 1, symptomatic, growing, unresectable, or recurrent	Surgery if safe decompression/pathology is needed; otherwise SRS/FSRT or fractionated RT based on size and optic/brainstem proximity.	SRS commonly 12-14 Gy x 1 for small lesions away from optic structures; FSRT 25 Gy / 5 or conventional RT 50.4-54 Gy.
Grade 2 after GTR	Discuss adjuvant RT vs close observation/trial. Board-style scenarios often favor RT if brain invasion, high mitotic index, high-risk location, or molecular concern.	54-59.4 Gy; RTOG 0539 intermediate-risk regimen used 54 Gy.
Grade 2 after STR or recurrent grade 2	Adjuvant/salvage RT is generally recommended because recurrence risk is high.	Commonly 59.4-66 Gy with generous dural CTV; selected dose escalation must respect brain/optic constraints.
Grade 3 or molecularly grade 3	Adjuvant RT even after GTR; systemic/radioligand/immunotherapy approaches remain trial-oriented for progression.	Usually 60 Gy (per RTOG 0539 high-risk), but dose escalation to 60-66 Gy is favored to improve PFS based on retrospective data.

WHO 2021 Molecular Reclassification Matters

TERT promoter mutation or CDKN2A/B homozygous deletion upgrades meningioma to WHO grade 3. That is a very testable modern pathology point.

RTOG 0539 Risk Groups

Risk group	Definition	Treatment / result
Low risk	New grade 1, GTR or STR	Observation; favorable long-term PFS.
Intermediate risk	New grade 2 after GTR or recurrent grade 1 any EOR	54 Gy; 3y PFS about 94%.
High risk	Grade 3 any EOR, recurrent grade 2 any EOR, or new grade 2 after STR	60 Gy high-dose region + 54 Gy low-dose region; recurrence risk remains substantial.

Grade 2-3 Dose Escalation: Retrospective cohorts (e.g., Zeng et al.) show that dose escalation for high-grade meningiomas beyond the standard 60 Gy (e.g., >66 Gy) significantly improves progression-free survival compared to standard-dose cohorts.

CTV Margin Rules to Memorize

Grade	CTV principle
Grade 1	No CTV margin for well-defined gross disease; respect bone/dural anatomy.
Grade 2	0.5-1 cm generous dural margin; up to 5 mm into brain parenchyma for microscopic brain invasion.
Grade 3	1-2 cm CTV, anatomically constrained.

Planning tools: CT bone window, MRI T1 post-contrast, T2-weighted and skull-base fat-sat sequences. DOTATATE PET can help define extent because most meningiomas express somatostatin receptor.

SRS caution: extensive pretreatment edema, large convexity/parasagittal tumors, sagittal sinus compromise, high-grade histology, and broad tumor-brain interface increase post-SRS edema risk. Fractionated RT/FSRT is often the cleaner answer near optic apparatus, brainstem, or when edema risk is high.

PART VI - PRIMARY CNS LYMPHOMA

Management Paradigm + Dose Anchors

Clinical setting	Default management frame	RT / dose anchor
Newly diagnosed, fit PCNSL	Obtain tissue diagnosis, then high-dose methotrexate-based induction. For fit/eligible patients, high-dose chemotherapy/ASCT is often the preferred consolidation frame; reduced-dose WBRT remains an important alternative when RT consolidation is selected.	After CR, if RT consolidation is used, reduced-dose WBRT anchor 23.4 Gy / 13 fx.
Partial response after induction	Use consolidation strategy based on response and fitness; WBRT is more compelling if residual disease persists and patient can tolerate late neurotoxicity risk.	WBRT 30-36 Gy with boost to total about 45 Gy / 25 fx.
Older patient, especially >60	Avoid reflex high-dose WBRT because neurocognitive toxicity is a major competing risk. Favor systemic consolidation, reduced-dose RT only in selected patients, or palliative RT for refractory symptoms.	Use the lowest regimen that fits intent; avoid routine 45 Gy WBRT consolidation after CR in older adults.
Relapsed / refractory or poor PS	Clinical trial, salvage systemic therapy, ASCT if fit, or palliative WBRT/focal RT depending on symptoms and distribution.	Palliative WBRT commonly 20 Gy / 5 to 30 Gy / 10; definitive salvage individualized.

PCNSL Board Traps

Hold corticosteroids before biopsy whenever medically safe. Steroids can cause rapid radiographic regression and nondiagnostic pathology. If steroids were required and biopsy is nondiagnostic, stop steroids when safe and repeat biopsy or repeat CSF evaluation.

Surgery: stereotactic biopsy is usually preferred; resection is not routine because PCNSL is chemo-sensitive and often multifocal/deep.
RT alone: gives poor durability compared with modern methotrexate-based therapy and is usually palliative or salvage.

PCNSL Workup Checklist

Category	High-yield components
Clinical	Detailed neurologic exam, KPS/MMSE or cognitive baseline, lymph node exam, testicular exam in older men.
Labs	CBC/CMP with renal function for methotrexate eligibility, LDH, HIV testing; hepatitis testing as clinically appropriate.
CNS staging	MRI brain with contrast; MRI spine if spinal symptoms or CSF positivity; lumbar puncture when safe with cytology/flow and supportive molecular studies.
Ocular staging	Ophthalmologic exam with slit lamp because vitreoretinal lymphoma changes treatment and surveillance.
Systemic exclusion	PET/CT or CT chest/abdomen/pelvis; bone marrow biopsy in selected patients; testicular ultrasound in older men if exam/suspicion warrants.

PCNSL Evidence Hooks

RTOG 8315 is a classic reminder that RT alone has limited long-term disease control in PCNSL.

Reduced-dose WBRT series support 23.4 Gy after complete response to methotrexate-based induction as a way to preserve disease control while lowering neurotoxicity.

RTOG 1114 supports a PFS benefit for adding low-dose WBRT after induction/consolidation compared with systemic therapy alone, but neurotoxicity and patient age remain central.

PRECIS supports ASCT as an important consolidation alternative, with less neurotoxicity than high-dose WBRT in fit patients.

PART VII - BENIGN, SKULL-BASE, OCULAR, AND FUNCTIONAL CNS

Pituitary Neuroendocrine Tumor / Pituitary Adenoma

Scenario	Management pearl	Dose / constraint
Prolactinoma	Dopamine agonist is first-line. Surgery is considered if medical therapy fails, is not tolerated, pregnancy is desired in selected cases, or apoplexy/urgent decompression occurs.	RT is uncommon upfront.
Nonfunctioning macroadenoma / optic compression	Surgery is typical first-line for decompression. Observe stable microadenomas; RT is for residual/recurrent growth or unresectable disease.	Fractionated RT/FSRT 45-50.4 Gy; SRS 14-20 Gy x 1 when optic geometry is safe.
Secretory PitNET persistent after surgery/medical therapy	RT improves tumor and hormonal control, but hormone normalization can take years. Suppressive medical therapy is commonly held about 1 month before RT and resumed afterward when clinically appropriate.	Fractionated RT 50.4-54 Gy; SRS usually ≥20 Gy x 1.
Optic-adjacent disease	Use conventional fractionation when tumor is too close to the optic apparatus; SRS is generally reserved for a safe gap and strict optic constraints.	Optic max roughly 8-10 Gy x 1, 17.4 Gy / 3, 25 Gy / 5, or 54 Gy conventional.

Vestibular Schwannoma

Clinical setting	Default management	RT / planning anchor
Small/medium, good hearing, asymptomatic or minimally symptomatic	Observation with MRI every 6-12 months is reasonable for small, nongrowing tumors. Upfront SRS is also reasonable in selected patients with growth, preference for treatment, limited follow-up reliability, or anatomy where later growth would make treatment harder.	No immediate RT is often appropriate, but not mandatory in every well-selected patient.
Small/medium, growing or symptomatic, no major brainstem compression	SRS is favored for tumor control with low facial/trigeminal toxicity when dose is kept conservative.	Marginal dose 12-13 Gy x 1; avoid doses >13 Gy when possible.
Large Koos IV / brainstem shift / cystic or decompression needed	Surgery is often preferred first and may be necessary when decompression matters; RT can be used after STR or at progression.	Use FSRT if geometry is unfavorable for SRS.
Hearing preservation constraints	Cochlear dose is a key planning endpoint, but hearing decline can still occur from tumor, age, and treatment.	Single-fx cochlea mean <4 Gy; brainstem Dmax ideally around <12 Gy when feasible, with D0.03cc <15 Gy as a common hard-stop style anchor.

Koos grading: I intracanalicular; II extends into CPA without brainstem contact; III compresses brainstem without shift; IV compresses and shifts brainstem.

V-REX: upfront radiosurgery improved radiographic tumor-volume outcomes compared with observation, but symptom/QOL differences were less decisive. Good board phrasing: observation is reasonable for small, nongrowing, asymptomatic tumors; upfront SRS is reasonable when growth, patient preference, or anatomy favors treatment.

Trigeminal Neuralgia

Medical first-line: carbamazepine or oxcarbazepine. Procedure standard: microvascular decompression is the durable surgical benchmark for appropriate candidates. Other procedural options include percutaneous rhizotomy approaches such as radiofrequency, glycerol, or balloon compression. SRS role: medically refractory patients who are not good candidates for surgery or prefer a noninvasive approach.

SRS target	Dose	Board toxicity pearl
4-mm shot to trigeminal root entry zone / proximal trigeminal nerve	70-90 Gy x 1 to maximum dose	Facial numbness/paresthesia is dose- and series-dependent, roughly 10-40% depending on definition and follow-up; bothersome numbness is lower, and anesthesia dolorosa is rare.

Functional and Vascular Radiosurgery

Indication	Role	Dose / pearl
VIM thalamotomy for tremor	Consider for medically refractory essential tremor or tremor-dominant Parkinson disease when DBS or focused ultrasound is not appropriate or desired.	Gamma Knife maximum dose commonly 130-140 Gy to VIM; response is delayed over months and adverse effects can also be delayed.
Brain AVM	SRS is best for small-to-moderate AVMs, deep/eloquent locations, or residual AVM after embolization/surgery.	Margin dose often about 18-25 Gy by volume/OARs; obliteration takes 2-3+ years, so latency hemorrhage risk persists.
Dural AVF	Embolization/surgery dominate for high-risk cortical venous drainage. SRS can be considered for selected residual/refractory lesions where immediate cure is not required.	Latency to obliteration matters; not the first answer for aggressive symptomatic high-risk dAVF.

Uveal Melanoma

Scenario	Management pearl	Dose / planning anchor
Small, low suspicion choroidal lesion	Observation is reasonable if fewer high-risk features are present; treat for growth or symptoms.	Serial ophthalmic exam and imaging.
Small to medium uveal melanoma	Vision-sparing definitive RT is standard: episcleral plaque brachytherapy or charged-particle RT. Diagnosis is often clinical by ocular oncology exam plus ultrasound.	Plaque: 85 Gy to tumor apex from inner sclera, with plaque typically in place 3-7 days.
Large tumor / blind painful eye / extensive extraocular extension	Enucleation remains appropriate when globe-sparing RT is not feasible or unlikely to preserve function.	Particle RT can be considered for selected large tumors.
Proton / charged-particle RT	Useful for posterior, large, or anatomically challenging tumors; tantalum markers assist localization.	Common proton anchor 56-60 GyE / 4 fx; some regimens up to 70 GyE / 5 fx.

Do not confuse uveal melanoma with cutaneous melanoma. Uveal melanoma is not typically BRAF/NRAS-driven, spreads hematogenously, and liver staging is essential at diagnosis.

Practice nuance: Gamma Knife or linac radiosurgery is used at some centers for selected uveal melanomas, often with retrobulbar block/akinesia and ophthalmic immobilization. Plaque brachytherapy and proton/charged-particle RT remain the cleaner board anchors.

Small-lesion risk features: symptoms, diameter >5 mm, thickness >2 mm, subretinal fluid or orange pigment, tumor within 3 mm of optic disc, ultrasound hollowness, and absence of halo. Fewer risk features supports surveillance; growth supports treatment.

Poor prognostic factors: large thickness/diameter, ciliary body involvement, epithelioid histology, older age, monosomy 3/8q gain, and gene-expression profile class 2.

Skull-Base Chordoma / Chondrosarcoma

Maximal safe resection plus high-dose conformal RT is the default frame because durable control requires dose near critical skull-base OARs. Protons or carbon ions are often preferred when available. Chordoma is generally more aggressive and more dose-demanding than low-grade chondrosarcoma.

Entity	Dose anchor	Planning pearl
Skull-base chordoma	70-78 Gy(RBE)	Composite optic pathway, brainstem, temporal lobe, and cranial nerve risk drive plan quality.
Low-grade skull-base chondrosarcoma	66-70 Gy(RBE)	Often more indolent and more radiosensitive than chordoma, but still requires high-dose conformal RT.

PART VIII - PEDIATRIC CNS QUICK HITS

Pediatric Board Anchors

Compact pediatric CNS entities that fill the biggest gap in the adult-heavy page; see the pediatric review page for the fuller disease-specific staging and dose tables.

Entity	Management frame	Dose / board anchor
Average-risk medulloblastoma	Age ≥3, M0, residual ≤1.5 cm2, favorable histology after maximal safe resection. CSI + involved-field boost + chemotherapy.	CSI 23.4 Gy / 13 fx + boost 30.6 Gy / 17 fx to total 54 Gy. Avoid 18 Gy CSI outside protocol.
High-risk medulloblastoma	Metastatic disease, residual >1.5 cm2, poor histology, or very young age. Treat with higher-dose CSI, boost, and multiagent chemotherapy; infants require risk-adapted strategies.	CSI 36 Gy / 20 fx + posterior fossa/tumor-bed boost to 54-55.8 Gy; spinal metastasis boost often 45 Gy.
Pediatric ependymoma	Maximal safe resection is the key prognostic step. Postoperative focal conformal RT is standard for most intracranial grade 2/3 tumors; CSI only for dissemination.	Focal RT 54-59.4 Gy; limited-volume target around cavity/residual with about 1 cm CTV in classic protocols.
Diffuse midline glioma / DIPG	Surgery usually not feasible. RT alone remains the standard palliative backbone; systemic therapy and dose escalation have not clearly improved survival.	54 Gy / 30 fx; median survival typically <1 year. Re-RT can palliate selected progression.
Craniopharyngioma	GTR alone can control disease but may be morbid; STR + RT often provides comparable control with less hypothalamic/optic injury. Monitor cyst size during treatment.	Conventional RT/PBT 54 Gy / 30 fx; on-treatment MRI every 1-2 weeks if cystic fluctuation is a concern.
Intracranial germinoma	Check serum and CSF β-hCG/AFP and image brain/spine. Bifocal pineal + suprasellar disease is not automatically metastatic. Chemo followed by whole-ventricle RT is standard for localized pure germinoma.	Conservative board anchor after chemo: WVI 24 Gy + tumor-bed boost 12 Gy. Response-adapted 18 Gy WVI is trial/de-escalation nuance, not the default. Metastatic disease uses CSI, often 21-24 Gy + boost after chemo.
NGGCT	Markers define diagnosis and risk. Multiagent chemotherapy followed by RT; second-look surgery if markers normalize but residual mass persists.	Classic RT standard is CSI 36 Gy + boost 18 Gy; WVI de-escalation has been studied but spine failures are a caution.
ATRT	Rare aggressive tumor in infants/young children; defined by SMARCB1 loss. Multimodality therapy with surgery, intensive chemotherapy, and RT is standard when feasible.	Focal RT often 50.4 Gy if <3 years and 54 Gy if older; CSI 23.4-36 Gy + boost may be considered for metastatic disease.

PART IX - BRAIN TUMOR RE-IRRADIATION

Management Paradigm + Dose Anchors

Scenario	Selection frame	RT / dose anchor
Brain metastasis after prior WBRT	SRS/FSRS is often feasible for limited relapse if performance status, systemic options, and normal-brain dose are acceptable. RTOG 9005 is both the classic single-fraction size ladder and a re-irradiation trial: eligible patients had recurrent/progressive tumors after prior cranial RT.	Use SRS/FSRS dose by size with extra attention to cumulative brain V12/V20/V24, lesion location, and prior WBRT dose.
Recurrent glioblastoma / grade 4 glioma	Best for focal recurrence, interval usually ≥6-12 months, KPS preserved, volume modest, and no diffuse/leptomeningeal progression. RTOG 1205 used 35 Gy / 10 with bevacizumab and improved PFS but not OS.	Common anchors: 25-35 Gy / 5-10 fx; consider bevacizumab when edema/radionecrosis risk is high.
Recurrent meningioma or benign skull-base tumor	Proceed only after careful surgical/pathology review because patients can live years with toxicity; fractionate when optic apparatus/brainstem/cochlea are limiting.	SRS/FSRT or conventional re-RT individualized; cumulative optic/brainstem/cochlea dose drives the plan more than nominal prescription.
Poor prognosis or diffuse recurrence	Supportive care, steroids, surgery/LITT for focal mass effect, systemic therapy, or short palliative RT may be better than aggressive re-irradiation.	Use the shortest regimen that plausibly improves symptoms; avoid treating scans when toxicity risk exceeds realistic benefit.

Clinical Selection + Counseling

Domain	Favorable for re-RT	Unfavorable / caution
Performance and prognosis	KPS ≥60-70 or ECOG 0-2, expected survival long enough to benefit, patient can tolerate simulation/treatment logistics.	ECOG >2, rapidly declining status, high symptom burden, very short prognosis, or treatment burden likely to dominate remaining quality of life.
Disease pattern	Focal, circumscribed recurrence; modest volume; limited overlap with critical OARs; no diffuse leptomeningeal or explosive multifocal pattern.	Large volume, diffuse/multifocal recurrence, deep bilateral/medial involvement, major overlap with optic apparatus/brainstem, or uncertain progression vs necrosis when management would change.
Interval and prior RT	Interval usually ≥6 months, ideally ≥12 months; prior dose distribution available; OAR cumulative dose acceptable.	Very short interval, missing prior plan/dose, prior OAR dose already near tolerance, or prior severe RT toxicity.
Counseling frame	Goal is often local control, steroid reduction, slowing neurologic decline, or delaying progression.	Established aphasia, plegia, severe visual loss, or fixed neurocognitive deficits rarely reverse. Re-RT may prevent worsening but should not be sold as neurologic restoration.

Clinical Selection + Technical Principles

Typical minimum interval: at least 6 months from prior RT, ideally ≥1 year.
Use tight margins: 0-5 mm CTV.
Get prior DICOMs whenever possible and review 3D cumulative dose.
Think in cumulative EQD2 with an explicit tissue-recovery assumption; a 50% recovery sensitivity estimate is sometimes used depending on interval, dose, and clinical context.
Be especially cautious with medial tumors, where cumulative dose to the contralateral hemisphere can produce bilateral deficits.

EQD2 / BED Mechanics

BED: n x d x (1 + d / (alpha/beta))
EQD2: BED / (1 + 2 / (alpha/beta))
Typical alpha/beta assumptions: tumor about 10 Gy; late brain, optic pathways, and brainstem often 2-3 Gy. State the alpha/beta you used. The 2026 corrigendum to the ESTRO/EANO reirradiation recommendation is a good reminder that the wrong alpha/beta changes the dose-sum interpretation. The ESTRO/EORTC re-irradiation consensus is the cleaner source for how to define and report re-irradiation.

Re-Irradiation Plan Analysis

Step	What to do	Why it matters
Prior data	Import prior CT, structure set, dose, and plan when possible; document if you only have PDFs or prescription summaries.	Re-irradiation decisions are only as good as the old dose reconstruction.
Registration	Use rigid registration for skull/brain as baseline; use deformable registration cautiously and inspect anatomy, cavities, and shifted ventricles.	A numerically pretty dose sum can be biologically misleading if anatomy changed.
Dose math	Sum physical dose only when fraction size is comparable; otherwise convert to BED/EQD2 with explicit alpha/beta assumptions, commonly ~2 Gy for late brain/OAR and ~10 Gy for tumor.	Plan review should state assumptions, not hide them inside a spreadsheet.
Recovery assumption	Run sensitivity estimates such as no recovery vs 25-50% recovery depending on interval, tissue, prior dose, and clinical urgency.	There is no universal forgiveness number; recovery is a clinical assumption.
Brain OARs	Inspect optic nerves/chiasm, brainstem, cochlea, hippocampi when relevant, temporal lobes, and uninvolved brain V12/V20/V24.	If prior optic/brainstem dose was near tolerance, incremental re-RT dose should be very low or fractionated with extreme caution.

Safe cumulative dose framing: avoid presenting a single universal cumulative brainstem/optic limit. A reasonable board-facing answer is to quote the conventional initial tolerances, calculate cumulative EQD2/BED, consider interval/recovery, and make the re-RT plan prove that incremental dose to optic apparatus and brainstem is acceptable. For focal recurrent glioblastoma, 2024 pattern-of-care data show ongoing heterogeneity, which is exactly why transparent plan-sum assumptions matter.

Cumulative Dose Heuristics

Structure / metric	Practical discussion range	How to say it on boards
Normal brain	Older reviews report low necrosis risk when cumulative EQD2 is <~96 Gy; small focal volumes may tolerate ~100-120 Gy, with risk rising by dose, volume, fraction size, and overlap.	Do not give a lifetime whole-brain number. Discuss cumulative EQD2, high-dose volume, V12/V20/V24, location, symptoms, and interval.
Brainstem	Candidate cumulative max/near-max EQD2 discussion range roughly 85-100 Gy, highly volume- and fractionation-dependent.	If prior brainstem dose was near tolerance, keep incremental dose very low or use fractionation. A 100 Gy heuristic is not a license.
Optic nerves / chiasm	Conservative candidate cumulative max/near-max EQD2 discussion range roughly 75-80 Gy; some institutional heuristics are higher, but optic toxicity is unforgiving.	Be more conservative than for brainstem. Document baseline vision and counsel explicitly about visual risk.
Recovery factor	No recovery, 25%, and 50% recovery sensitivity estimates are common ways to stress-test the plan.	Recovery is an assumption, not a fact. State whether it was applied to physical dose before conversion or to BED/EQD2 after conversion.

SRS / FSRS Data Anchors in Re-Irradiation

Study / pattern	Setting	Board-useful takeaway
RTOG 9005	Recurrent, previously irradiated primary brain tumors or brain metastases treated with single-fraction SRS.	This is why the 24 / 18 / 15 Gy size ladder belongs in re-irradiation discussions, not only intact-met dosing tables.
RTOG 1205	Recurrent glioblastoma, ≥6 months after prior chemoRT; bevacizumab +/- reRT.	35 Gy / 10 with bevacizumab improved PFS but not OS; it is the clean prospective modern anchor.
Small-volume SRS / FSRS series	Selected focal recurrent high-grade glioma or metastasis relapse after prior RT.	SRS doses around 12-16 Gy x 1 or FSRS regimens such as 25-35 Gy / 5-10 are used selectively; target volume and normal-brain dose matter more than nominal prescription.

CROSS-CUTTING HIGH-YIELD POINTS

Symptomatic brain metastases still need upfront local therapy, even in the era of CNS-active systemic agents.
Deferring RT is most defensible in carefully selected asymptomatic patients with strong CNS-active drugs and reliable follow-up, especially EGFR- or ALK-driven NSCLC.
N0574 made SRS alone standard over SRS + WBRT for 1-3 brain metastases because of cognitive preservation.
Level I evidence for SRS now extends to up to 20 lesions in selected patients.
Intact-met SRS: RTOG 9005 defines the classic size ladder; for <2 cm lesions, 20-24 Gy is common, but 24 Gy was the protocol upper dose rather than a mandatory dose for every small lesion.
Post-op cavity management: postoperative SRS is preferred over WBRT and better than observation for local control.
HA-WBRT + memantine is preferred for many WBRT candidates when hippocampal avoidance is oncologically safe.
Glioblastoma, IDH-wildtype standard: 60 Gy / 30 + concurrent/adjuvant TMZ, including molecular glioblastoma.
IDH-mutant astrocytoma grade 4: do not call it glioblastoma in WHO 2021; CDKN2A/B homozygous deletion upgrades IDH-mutant astrocytoma to grade 4.
Elderly/frail glioblastoma: 40.05 Gy / 15 + TMZ for fit older patients; 25 Gy / 5 is a real option for elderly/frail or high treatment-burden patients.
High-risk LGG: RTOG 9802 established RT -> PCV as the OS-improving standard.
INDIGO made vorasidenib relevant for residual/recurrent non-enhancing grade 2 IDH-mutant glioma when delaying RT/chemo is desirable, but it does not replace standard adjuvant CRT for clearly high-risk disease.
Meningioma WHO 2021: TERT promoter mutation or CDKN2A/B homozygous deletion upgrades to grade 3.
PCNSL trap: hold steroids before biopsy if medically safe; high-dose methotrexate-based induction is the backbone.
PitNET trap: prolactinoma is medically managed first; fractionate when too close to optic pathways.
Vestibular schwannoma: observe many small, nongrowing, asymptomatic tumors; SRS anchor 12-13 Gy; large brainstem-compressive tumors often need surgery or at least surgical evaluation first.
Uveal melanoma: liver staging is essential; plaque 85 Gy or proton 56-60 GyE / 4 are key dose anchors.
Medulloblastoma: average-risk CSI 23.4 Gy + boost to 54 Gy; high-risk CSI about 36 Gy + boost.
Ependymoma: focal RT 54-59.4 Gy; CSI only for dissemination.
Re-irradiation: select patients first, calculate second. Wait at least 6 months when possible, use tight margins, discuss goals realistically, and think in composite EQD2/BED rather than isolated plan doses.

CONSOLIDATED DOSE TABLE

Clinical setting	Dose / planning rule	Use case
RTOG 9005 intact-met SRS ladder	24 Gy ≤2 cm; 18 Gy 2.1-3 cm; 15 Gy 3.1-4 cm	Classic size-based maximum tolerated dose ladder from a re-irradiation trial in previously irradiated patients; 16-20 Gy may be used for selected small lesions depending on IDL, OARs, volume, and institutional practice.
N107C cavity single-fraction ladder	20 Gy <4.2 mL; 18 Gy 4.2-7.9; 17 Gy 8.0-14.3; 15 Gy 14.4-19.9; 14 Gy 20.0-29.9; 12 Gy ≥30 mL	Postoperative cavity SRS by volume; FSRS often used for large/irregular/dural-risk cavities.
Post-op cavity, larger / irregular	24-27 Gy / 3 fx	Fractionated postop SRS.
Post-op cavity, very challenging	30-32.5 Gy / 5 fx	Larger cavity / dural involvement / FSRS.
Single-fraction SRS constraint	Brain V12 ≤10 cc	Necrosis mitigation.
FSRS cavity constraint	Brain + target V20Gy (3 fx) or V24Gy (5 fx) <20 cc	Post-op FSRS planning.
HA-WBRT hippocampi	D100% ≤9 Gy; Dmax ≤16 Gy	NRG-CC001 / RTOG 0933 style planning; use RTOG 0933 contouring guidance.
HA-WBRT / conventional WBRT	30 Gy / 10 fx	Extensive brain metastases with reasonable prognosis when SRS not suitable.
Short palliative WBRT	20 Gy / 5 fx	Poor prognosis or logistical-burden-sensitive palliation.
Standard glioblastoma, IDH-wildtype	60 Gy / 30 fx	Fit adults, including molecular glioblastoma.
Elderly glioblastoma + TMZ	40.05 Gy / 15 fx	Modern standard for older fit patients.
Very short-course glioblastoma RT	25 Gy / 5 fx	Elderly/frail or high treatment-burden scenario.
Grade 2 IDHm oligodendroglioma	50.4 Gy	Common definitive / adjuvant dose.
Grade 2 IDHm astrocytoma	54 Gy	Common definitive / adjuvant dose.
Grade 3 IDHm oligodendroglioma	59.4 Gy / 33	RT before PCV/TMZ.
Grade 3 IDHm astrocytoma	59.4 Gy / 33	RT before TMZ.
Intermediate-risk meningioma	54 Gy	RTOG 0539 group 2.
High-risk meningioma	60 Gy	RTOG 0539 high-dose region.
Grade 2 STR / recurrent grade 2 or grade 3 meningioma	60-66 Gy	Common dose-escalated range; Rogers/Zeng data support >60 Gy for grade 3 to improve PFS. Fractionated RT preferred.
PCNSL after CR	23.4 Gy / 13 fx	If RT consolidation is chosen; ASCT is often preferred for fit/eligible patients.
PCNSL partial response	30-36 Gy + boost to about 45 Gy / 25 fx	Residual disease after induction when RT consolidation is selected.
PitNET nonsecretory FSRT	45-50.4 Gy	Residual/recurrent adenoma or optic-adjacent disease.
PitNET secretory FSRT	50.4-54 Gy	Persistent hormone secretion after surgery/medical therapy.
PitNET SRS	14-20 Gy nonsecretory; ≥20 Gy secretory	Use when optic pathway geometry is safe.
Optic pathway SRS/FSRS constraints	8-10 Gy x 1; 17.4-20 Gy / 3; 25 Gy / 5; 54 Gy conventional	HyTEC: RION risk is low when max point dose is <10 Gy x1, <20 Gy/3, and <25 Gy/5 in patients without prior RT.
Vestibular schwannoma SRS	12-13 Gy x 1	Small/medium tumors without major brainstem compression.
Vestibular schwannoma constraints	Brainstem Dmax ideal <12 Gy, D0.03cc <15 Gy; cochlea mean <4 Gy	Single-fraction planning anchors.
Trigeminal neuralgia SRS	70-90 Gy x 1	4-mm shot to root entry zone / proximal nerve.
Uveal melanoma plaque	85 Gy	Prescribed to tumor apex from inner scleral surface.
Uveal melanoma proton	56-60 GyE / 4 fx	Common charged-particle regimen; selected regimens up to 70 GyE / 5.
Skull-base chordoma	70-78 Gy(RBE)	Postop definitive high-dose conformal/particle RT.
Skull-base low-grade chondrosarcoma	66-70 Gy(RBE)	Postop definitive high-dose conformal/particle RT.
Average-risk medulloblastoma	CSI 23.4 Gy / 13 + boost to 54 Gy	Age ≥3, M0, favorable postop risk.
High-risk medulloblastoma	CSI 36 Gy / 20 + boost to 54-55.8 Gy	Metastatic/residual/poor histology or other high-risk features.
Pediatric ependymoma	54-59.4 Gy	Focal postoperative RT; CSI only for dissemination.
Diffuse midline glioma / DIPG	54 Gy / 30 fx	Standard palliative RT backbone.
Craniopharyngioma	54 Gy / 30 fx	STR + RT or definitive/adjuvant conformal RT.
Localized germinoma after chemo	WVI 24 Gy + boost 12 Gy	Conservative board anchor; 18 Gy WVI is response-adapted trial nuance.
NGGCT classic anchor	CSI 36 Gy + boost 18 Gy	Classic standard after chemotherapy.
Recurrent glioblastoma re-irradiation	25-35 Gy / 5-10 fx	Selected focal recurrence with favorable interval/volume; RTOG 1205 used 35 Gy/10 with bevacizumab.
Small-volume SRS re-irradiation	12-16 Gy x 1	Selected very small focal recurrences away from critical OARs; RTOG 9005 provides the historical single-fraction reRT context.
Re-irradiation margin	CTV 0-5 mm	Tight composite-dose planning.

KEY LANDMARK TRIALS / STUDIES (MEMORIZE)

Trial / study	Disease	One-line takeaway
CheckMate 204	Melanoma brain metastases	Symptomatic patients do poorly on immunotherapy alone; supports upfront local therapy.
CROWN	ALK+ NSCLC brain metastases	Lorlatinib has very high intracranial activity and can justify deferred RT in selected asymptomatic patients.
N0574	1-3 brain metastases	SRS alone preserves cognition and QOL compared with SRS + WBRT, without OS loss.
RTOG 9005	Previously irradiated brain tumors / brain metastases	Re-irradiation-era maximum tolerated dose ladder for single-fraction SRS: 24, 18, and 15 Gy by diameter.
Yamamoto / JLGK0901	1-10 brain metastases	Prospective observational support for SRS alone in selected patients with up to 10 lesions.
Aizer 2026	5-20 brain metastases	SRS outperformed HA-WBRT for symptom burden in selected multi-metastasis patients.
METIS	NSCLC brain metastases after SRS	TTFields prolonged time to intracranial progression without worsening QOL/cognition; not yet a routine board-default add-on.
N107C	Resected brain metastasis	Post-op SRS beats WBRT for cognitive preservation without sacrificing OS.
Mahajan 2017	Resected 1-3 brain metastases	Post-op SRS improves local control compared with observation.
RTOG 0614	WBRT candidates	Memantine reduces cognitive decline after WBRT.
NRG-CC001	WBRT candidates	HA-WBRT + memantine is the modern preferred WBRT approach when feasible.
QUARTZ	Poor-prognosis NSCLC brain metastases	Supports avoiding reflex WBRT when supportive care is equally appropriate.
Stupp / EORTC-NCIC	Newly diagnosed glioblastoma	60 Gy / 30 with concurrent/adjuvant TMZ established the standard backbone.
EF-14	Newly diagnosed glioblastoma	Tumor treating fields plus adjuvant TMZ improved survival in selected patients after chemoradiation.
Perry 2017	Elderly glioblastoma	40.05 Gy / 15 + TMZ improves OS over RT alone.
Roa 2004 / IAEA short-course	Elderly/frail glioblastoma	Supports shorter RT regimens including 40 Gy / 15 and, in selected elderly/frail patients, 25 Gy / 5.
RTOG 1205	Recurrent glioblastoma	35 Gy / 10 with bevacizumab improved PFS but not OS compared with bevacizumab alone.
ESTRO/EORTC re-irradiation consensus	Re-irradiation reporting	Consensus framework for definition, clinical decision-making, dose accumulation, and reporting standards.
RTOG 9802	High-risk LGG	RT -> PCV confers a major OS benefit.
EORTC 22845	Grade 2 glioma	Early RT improves PFS and seizure control, not OS.
EORTC 22033-26033	High-risk grade 2 glioma	TMZ monotherapy did not improve PFS/QOL/cognition compared with RT alone; RT-based therapy remains central.
CATNON	Grade 3 IDH-mutant astrocytoma	Adjuvant TMZ after RT improves outcomes; concurrent TMZ contribution is less clear.
RTOG 9402 / EORTC 26951	1p/19q-codeleted grade 3 oligodendroglioma	RT + PCV provides long-term survival benefit in codeleted disease.
INDIGO	IDHm grade 2 glioma	Vorasidenib delays progression and time to next intervention.
Vorasidenib commentary	IDHm grade 2 glioma	Frames the practical question of which patients benefit from delaying RT/chemo with an IDH inhibitor.
RTOG 0539	Meningioma	Risk-stratified outcomes framework for grade / recurrence / extent of resection.
Zeng et al.	Grade 2-3 Meningioma	Dose escalation > 66 Gy significantly improves PFS compared to standard dose cohort.
RTOG 8315	PCNSL	RT alone produced limited durability, reinforcing that HD-methotrexate-based therapy is the backbone.
RTOG 1114	PCNSL	Supports PFS benefit from adding low-dose WBRT after methotrexate-based therapy in selected patients.
PRECIS	PCNSL	ASCT is an important consolidation option with less neurotoxicity than high-dose WBRT.
V-REX	Vestibular schwannoma	Upfront SRS reduces tumor volume vs observation, but symptom/QOL benefits are less clear.
COMS	Uveal melanoma	Plaque brachytherapy preserves the eye with survival comparable to enucleation for medium tumors.
ACNS0331 / ACNS0332	Medulloblastoma	Define modern risk-adapted CSI/boost/chemotherapy frameworks; avoid low-dose CSI outside protocol.
Merchant / St. Jude	Pediatric ependymoma	Limited-volume postoperative conformal RT achieves high control; extent of resection is crucial.
ACNS0121	Pediatric ependymoma	Immediate conformal RT appeared beneficial across strata and remains a key standard.
ACNS1123	Intracranial germ cell tumors	Response-adapted RT supports WVI de-escalation for germinoma; NGGCT WVI de-escalation had spine failure concerns.
2024 re-irradiation pattern-of-care	Recurrent glioblastoma	Highlights real-world heterogeneity in recurrent glioblastoma re-RT and the need for explicit dose-sum assumptions.
HyTEC brain / HyTEC optic	CNS SRS constraints	Modern dose-volume tolerance references for radionecrosis and optic pathway risk.
NRG-BN001	Newly diagnosed glioblastoma	Dose intensification remains investigational; standard-dose chemoradiation still anchors care.
NRG-BN003 / BN015	Meningioma	Critical ongoing postop RT vs observation trials in grade 2 / molecularly high-risk disease.