Highlights
– The RANO four‑tier classification of residual T2‑FLAIR tumour volume (class 1: supramaximal beyond FLAIR; class 2: 0–5 cm3 remnant; class 3: 5–25 cm3; class 4: >25 cm3) stratifies long‑term outcomes in IDH‑mutant grade 2 glioma.
– Supramaximal resection (class 1) yielded the best outcomes (10‑year overall survival 98%; 5‑year PFS 83%), with graded decrement in outcomes across classes 2–4.
– Survival benefits of more extensive resection appear earlier in astrocytomas (separation by ~3 years) than in oligodendrogliomas (separation at 6–8 years), but benefit is present across molecular subtypes.
– The classification was robust in multivariable models, in patients receiving first‑line adjuvant therapy, and in an independent UCSF validation cohort.
