Stereotactic Radiosurgery · Evidence

Landmark Trials & Open Controversies

The randomized evidence that built SRS practice — and the questions still being argued

Radiosurgery is unusually well served by randomized trials for a procedural discipline. This page serves as the cross-cutting hub: a master index of the landmark trials (with the full disease-specific debates now developed on each disease page), followed by the controversies that span every SRS target — the validity of the linear-quadratic model at ablative dose, radionecrosis dosimetry, and the timing of radiosurgery with immunotherapy and systemic therapy.

Timoteo Almeida, MD, PhD | Department of Neurological Surgery

Orientation

Most SRS controversies share a structure: a treatment improves one endpoint (intracranial control, local control) while worsening another (neurocognition, distant failure, fracture), and the debate is about which patients should accept which trade. Reading the evidence well means holding the endpoint in view — a trial that is positive for local control may be neutral or negative for survival or quality of life, and the right choice depends on prognosis and goals.

Part I

Landmark Trials

1.Master trial index

The landmark trials are collected here for quick orientation, each linked to its primary publication on PubMed; the full disease-specific debate each one feeds is developed on the disease pages noted below the table.

Master index of landmark SRS/SBRT trials — trial (linked to PubMed) and headline result.
Trial	Headline result
Aoyama 2006 (JAMA)	Adding WBRT to SRS improved intracranial control, not survival
Chang 2009 (Lancet Oncol)	WBRT worsened learning/memory; favored SRS-alone + surveillance
Brown 2016 / N0574 (JAMA)	WBRT added control but more cognitive decline; no survival gain
JLGK0901 (2014, Lancet Oncol)	Survival non-inferior for 5–10 vs 2–4 mets
Mahajan 2017 / N107C 2017 (Lancet Oncol)	Cavity SRS improves local control; spares cognition vs WBRT
NRG CC001 (2020, JCO)	Hippocampal avoidance + memantine preserved cognition
RTOG 90-05 (2000)	Single-fraction MTD 24/18/15 Gy by size
RTOG 0631 (Ryu 2023)	Single-fraction spine SBRT vs cEBRT — no pain advantage (negative)
SC.24 (Sahgal 2021, Lancet Oncol)	Spine SBRT 24/2 — higher complete pain response (positive)
ARUBA (Mohr 2014, Lancet)	Medical management beat intervention for unruptured AVMs (short follow-up)
RTOG 0539 / EORTC 22042	Risk-adapted and high-dose RT benchmarks for meningioma by grade

Disease-specific debates now live on the disease pages The met-count ceiling, whole-brain avoidance, and preoperative-versus-postoperative cavity SRS are developed on the brain-metastases page; the RTOG 0631-versus-SC.24 contrast on the spine page; the ARUBA debate on the AVM page; grade II adjuvant timing on the meningioma page; and the hearing-preservation, drug-holiday, and dose-versus-numbness questions on the vestibular schwannoma, pituitary, and trigeminal/functional pages. What follows here is only what cuts across all of them.

Part II

Cross-Cutting Controversies

2.The linear-quadratic model at ablative dose

Whether the linear-quadratic model remains valid at the high doses per fraction used in SRS is a genuine radiobiologic controversy. One camp argues the LQ model overpredicts cell kill and that vascular/endothelial and immune mechanisms dominate above a threshold; the other holds that the LQ model, perhaps modified, still describes the data adequately. The practical consequence is uncertainty in dose-conversion (BED/EQD2) at ablative fractions — which is why clinical dose selection leans on empirical trial doses (RTOG 90-05, HyTEC) rather than model extrapolation. (Developed on the radiobiology page.)

3.Radionecrosis dosimetry

The V12Gy (volume receiving ≥12 Gy) is the most used predictor of symptomatic radionecrosis across every cranial target, but the exact threshold and how to fractionate large lesions to stay under it are debated; staged or fractionated SRS for large lesions and cavities is one response. The dilemma of distinguishing radionecrosis from progression, and the management ladder once it occurs, are common to mets, AVM, and benign tumors alike (developed on the adverse radiation effects page).

4.Radiosurgery with immunotherapy and systemic therapy

The combination and timing of SRS with immunotherapy and targeted agents — the possibility of synergy (and rare abscopal responses) versus increased radionecrosis risk — is an area of rapid, still-maturing evidence where concurrent versus sequenced delivery is not fully resolved. It applies most to brain metastases but raises the same radiobiologic questions wherever SRS meets an active systemic agent, which is why it sits here rather than on a single disease page.

Separating the tiers The disease-specific trials (WBRT and cognition, cavity SRS, spine SBRT regimens, ARUBA, meningioma grading) are summarized in the index above and argued in full on their disease pages. The genuinely cross-cutting and still-contested questions — LQ validity at ablative dose, exact V12Gy radionecrosis thresholds, and SRS–immunotherapy/systemic-therapy timing — are the substance of this page. Practice patterns and local preference fill the gaps where trials do not yet speak.

Key points

This page is the cross-cutting hub: a master trial index that links out, plus the controversies that span every SRS target. Disease-specific debates are developed on each disease page.
Read every SRS trial by its endpoint: local control, intracranial control, survival, cognition, and quality of life can diverge in the same study.
LQ-model validity at ablative dose is genuinely contested (Kirkpatrick vs Brown/Brenner); empirical trial doses, not BED extrapolation, guide prescribing.
V12Gy is the common radionecrosis predictor across cranial targets, but the exact threshold and large-lesion fractionation remain debated.
SRS with immunotherapy and systemic therapy — synergy and abscopal hopes versus radionecrosis risk, and concurrent versus sequenced timing — is rapidly evolving and unresolved.

References

Brown PD, Jaeckle K, Ballman KV, et al. Effect of radiosurgery alone vs radiosurgery with whole-brain radiation therapy on cognitive function in patients with 1 to 3 brain metastases (N0574). JAMA. 2016;316(4):401–409. PubMed
Yamamoto M, Serizawa T, Shuto T, et al. Stereotactic radiosurgery for patients with multiple brain metastases (JLGK0901): a multi-institutional prospective observational study. Lancet Oncol. 2014;15(4):387–395. PubMed
Brown PD, Ballman KV, Cerhan JH, et al. Postoperative stereotactic radiosurgery compared with whole brain radiotherapy for resected metastatic brain disease (NCCTG N107C/CEC.3). Lancet Oncol. 2017;18(8):1049–1060. PubMed
Mahajan A, Ahmed S, McAleer MF, et al. Post-operative stereotactic radiosurgery versus observation for completely resected brain metastases. Lancet Oncol. 2017;18(8):1040–1048. PubMed
Brown PD, Gondi V, Pugh S, et al. Hippocampal avoidance during whole-brain radiotherapy plus memantine (NRG Oncology CC001). J Clin Oncol. 2020;38(10):1019–1029. PMC
Sahgal A, Myrehaug SD, Siva S, et al. SBRT vs conventional RT for painful spinal metastases (SC.24/TROG 17.06). Lancet Oncol. 2021;22(7):1023–1033. PubMed

Educational synthesis for neurosurgery and radiation-oncology trainees; not a treatment directive. Full per-trial detail and PMIDs are on the corresponding disease pages, with key trial citations verified during review.