EORTC 22845
In adults with low-grade glioma, does early radiotherapy improve outcomes compared with radiotherapy deferred until progression?
Reported outcome visualization
Key results
Median PFS was 5.3 years with early RT versus 3.4 years with deferred RT (HR 0.59, 95% CI 0.45–0.77; P<.0001). Median OS was 7.4 versus 7.2 years (HR 0.97, 95% CI 0.71–1.34; P=.872). At one year, seizures were better controlled with early RT.
Absolute Effect
Median PFS was extended by 1.9 years, but this is a difference in medians and is not an NNT. OS benefit was not demonstrated; fixed-time survival differences suitable for NNT are not provided here.
NNT: Not quantifiable or not appropriate for this design/end point.
NNH: Not quantifiable from the verified fixed-time toxicity data used in this summary; see toxicity and treatment burden below.
Time-to-event interpretation: Hazard ratios and median survival are relative/time-to-event measures; they are not converted into NNT unless a fixed-time absolute event estimate is available.
Toxicity and treatment burden
Quality of life was not studied. Long-term neurocognitive effects were not comprehensively measured using modern methods; toxicity must be balanced against tumour symptoms and progression risk.
Follow-up, limitations and maturity
Follow-up: Long-term follow-up; median survival 7.4 vs 7.2 years.
Pre-molecular-classification era: histology does not map cleanly to current IDH-mutant astrocytoma/oligodendroglioma categories. Many control patients received RT at progression, complicating OS interpretation.
Clinical interpretation
Early RT delays progression and improves seizure control but did not improve OS compared with a strategy of careful observation and RT at progression.
Primary publication and sources
van den Bent MJ, et al. Lancet. 2005;366:985–990.
Current-practice context · reviewed 15 October 2026
EORTC 22845 predates integrated molecular diagnosis. Current treatment decisions use IDH status, 1p/19q codeletion, grade, symptoms, residual disease and expected treatment burden. In appropriate IDH-mutant grade 2 diffuse gliomas, RT with PCV is a guideline-supported approach; selected patients with favourable features may be observed. Do not use the historical histology-only trial to dictate treatment without molecular classification.
ASCO–SNO guideline for diffuse astrocytic and oligodendroglial tumours ↗