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.
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.
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.
| 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for 5–10 vs 2–4 mets; the prospective observational study that first pushed the count ceiling past four, now superseded for higher counts by randomized data |
| Aizer 2026 (JAMA) | Randomized phase 3 of SRS versus hippocampal-avoidance WBRT in 196 patients with 5–20 metastases: lower 6-month symptom burden and better cognition with SRS, no survival difference, less treated-lesion recurrence, more distant intracranial failure |
| CYBER-SPACE (2025, Neuro Oncol) | Single-center randomized phase 2 trial of SRS planned on the SPACE versus MPRAGE MRI sequence; the sequence comparison was null (12-month freedom from a WBRT indication 78.5% vs 76.0%, HR 0.84). Across both arms about 77% of 1–10-lesion patients avoided a WBRT indication at 12 months, which is supportive but single-arm evidence |
| Mahajan 2017 / N107C 2017 (Lancet Oncol) | Mahajan compared cavity SRS with observation (12-month cavity recurrence-free 72% vs 43%). N107C compared cavity SRS with WBRT: better cognitive-deterioration-free survival with SRS and no survival difference, at the cost of poorer surgical-bed and intracranial control than WBRT |
| Mallela 2024 (J Neurosurg) | Prospective phase II preoperative SRS showed feasibility and favorable leptomeningeal/steroid outcomes; phase III comparison remains pending |
| 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) |
| NRG/RTOG 0539 long-term analysis | Ten-year risk-adapted PFS benchmarks for low-, intermediate-, and high-risk meningioma. This trial used fractionated external beam radiotherapy and explicitly did not permit radiosurgery; it is the risk-stratification benchmark against which radiosurgical series are read, not a radiosurgery trial |
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 view is that the unmodified model may overpredict cell kill and underrepresent additional vascular, stromal, and immune effects; another is that the LQ model remains clinically useful within relevant dose ranges when interpreted cautiously. No single biologic threshold makes one mechanism suddenly dominant. The practical consequence is uncertainty in dose-conversion (BED/EQD2) at ablative fractions, which is why clinical dose selection leans on empirical trial doses and normal-tissue outcome data rather than model extrapolation alone. (Developed on the radiobiology page.)
3.Radionecrosis dosimetry
The V12Gy (the volume of brain receiving at least 12 Gy; report whether the structure is brain minus target or brain including target, because both conventions are in use and the HyTEC multifraction analogues are defined on brain plus target) is the most used single-fraction dosimetric correlate of symptomatic radionecrosis, but risk is continuous rather than governed by one universal cutoff and is modified by target type, location, prior radiation, systemic therapy, and fractionation. For multifraction SRS, regimen-specific normal-brain volumes replace a literal V12 threshold. The dilemma of distinguishing treatment effect from progression, and the management ladder once it occurs, are 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.
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
- El Shafie RA, et al. Stereotactic radiosurgery for 1–10 brain metastases to avoid whole-brain radiotherapy: results of the CYBER-SPACE randomized phase 2 trial. Neuro Oncol. 2025;27(2):479–491. 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.