CNS
Expert consensus, not trial data: useful for SRS/re-irradiation planning constraints and for the imaging workup of a growing post-RT lesion, but no outcome endpoint behind any recommendation.
EANO Consensus Statement on Radiation Necrosis
ForPost-cranial-RT pts with a new enhancing lesion, glioma or brain metastases
TL;DRDelphi consensus: 53/57 statements reached ≥80% agreement across 20 experts; perfusion MRI + amino acid PET preferred, bevacizumab for steroid-refractory RN.
The dose-volume numbers are the transferable part: V12Gy ~10 cm³ carrying 5-10% symptomatic necrosis in single-fraction SRS, and hypofractionated brain+target V20Gy (3fx) or V24Gy (5fx) <20 cm³ holding RN needing resection under 4%. That is a planning constraint, and it gates the single-session vs hypofractionated choice for larger or eloquent-region metastases.
For a patient 6-24 months out from SRS or cranial RT with a new enhancing lesion, this supports going to perfusion MRI plus amino acid PET before calling progression; it does not settle mixed lesions, where the panel still points to tissue.
The planning-relevant numbers: V12Gy ~10 cm³ carries 5-10% symptomatic necrosis after single-fraction SRS, while hypofractionated brain+target V20Gy (3fx) or V24Gy (5fx) <20 cm³ keeps RN requiring resection under 4%. Re-irradiation risk climbs to 25% above cumulative EQD2 130 Gy, which constrains repeat SRS for lesions over 2.0-3.0 cm.
Bevacizumab moves from rescue to a triggered step at steroid dependence >4 weeks or dexamethasone 8 mg/day, with four accepted dosing schemes and no evidence favouring one. The panel also flags added RN risk when SRS is combined with dual checkpoint blockade or antibody-drug conjugates, which bears on sequencing brain RT against systemic therapy.
Resection carries the lowest accepted agreement in the management table (80.0%) yet is positioned as giving diagnosis and definitive treatment in one step for accessible lesions. LITT reached 100% agreement as the option for treatment-resistant RN unsuitable for resection, which gives a documented pathway for the steroid-dependent or bevacizumab-cycling patient.
11 details 5 trials watching
Three-round Delphi. 57 statements drafted after literature review across epidemiology-pathophysiology (n=8), causes (n=10), imaging (n=10), histopathology (n=9), management (n=20), plus an exploratory research set of 8. Consensus prespecified at ≥80% agreement on a 5-point Likert scale.
The voting panel, not patients: 15 volunteers (2 radiation/clinical oncologists, 4 neuro-oncologists, 4 medical oncologists, 2 neurosurgeons, 1 neuropathologist, 1 neuroradiologist, 1 nuclear medicine physician), expanded by 5 more in round 1 (4 neuro-oncologists, 1 radiation/clinical oncologist) to 20 total. Clinically the scope is RN after RT for primary glial or metastatic brain tumors.
RN is called uncommon below EQD2 ~40 Gy (α/β 2 Gy), rising with dose per fraction, total dose and irradiated volume. V12Gy ~10 cm³ carries a 5-10% symptomatic necrosis risk after single-session SRS; for hypofractionated SRT, brain-plus-target V20Gy (3fx) or V24Gy (5fx) <20 cm³ associates with <10% any necrosis and <4% RN requiring resection. Re-irradiation risk stays under 10% at cumulative EQD2 100-110 Gy and reaches up to 25% above 130 Gy.
Consensus reached on 53 of 57 statements after three rounds. Diagnostic and management statements are tabulated separately in the details; the four that failed to reach 80% are not identified in the available text.
| Modality | Setting | Sensitivity | Specificity |
|---|---|---|---|
| T1 contrast-enhanced MRI alone | WHO grade 3-4 glioma | 68% | 77% |
| T1 contrast-enhanced MRI alone | Brain metastases | 79% | 76% |
| DSC rCBV | Grade 3-4 glioma | 87-90% | 86-88% |
| DSC rCBV | Brain metastases (418 lesions) | 83% | 78% |
| MR spectroscopy Cho/NAA | Glioma (455 pts) | 88% | 86% |
| Amino acid PET | Brain metastases (~400 pts) | 82% | 84% |
The document's practical contribution is a decision sequence rather than a new treatment: advanced MRI first, amino acid PET to add confidence, tissue when doubt persists, and treatment triggered only by symptoms of >7 days with increasing severity. Its most consequential position is moving bevacizumab from rescue to an expected next step at a defined steroid threshold (dependence >4 weeks or dexamethasone 8 mg/day), which is a lower bar than many centres apply.
Agreement percentages measure how a self-selected 20-person European panel voted, and the panel skews neuro-oncology (8 of 20) over radiation oncology (3 of 20) for a complication defined by dose and volume. FET and F-DOPA availability is largely European, so the imaging algorithm's top tier is not reproducible in most centres worldwide. The 4 non-consensus statements are not enumerated in the accessible text, so the reader cannot see where the panel actually split.
Delphi expert-opinion document, no efficacy endpoint. Agreement measured against opinion, not outcomes; authors state absence of Level 1 evidence and call for randomised trials.
- Optimal bevacizumab dose, interval and duration for symptomatic RN n=408 · primary completion 2028-07 · phase 3 bevacizumab vs dexamethasone, 1L sCRNrecruiting Corticodependent or Corticoresistant Brain Radionecrosis After Radiotherapy for Brain Metastases Phase 3n=84 · primary completion 2028-08 · randomised bev vs placebo in steroid-refractory RN
- Single-session SRS vs hypofractionated SRT for RN risk active Comparing Single vs Multiple Dose Radiation for Cancer Patients With Brain Metastasis and Receiving Immunotherapy Phase NAn=58 · primary completion 2028-03 · single vs fractionated SRS toxicity on ICIn=54 · primary completion 2029-02 · staged SRS vs FSRT, 2-5 cm mets, safety endpointn=504 · primary completion 2030-01 · phase 3 3x10 Gy SRT vs 1x20-25 Gy SRS
- Predictors of bevacizumab response and recurrence rate after treatment