SURG-19. PROGNOSTIC VALIDATION OF A NEW CLASSIFICATION SYSTEM FOR EXTENT OF RESECTION IN GLIOBLASTOMA: A REPORT OF THE RANO RESECT GROUP

Abstract BACKGROUND Terminology to describe extent of resection in glioblastoma is inconsistent across clinical trials. A surgical classification system was previously proposed based upon residual contrast-enhancing (CE) tumor. We aimed (I) explore the prognostic utility and (II) define how much removed non-CE tumor translates into a survival benefit. METHODS The international RANO resect group retrospectively searched databases from seven neuro-oncological centers USA Europe for patients with newly diagnosed per WHO 2021 classification. Clinical volumetric information pre- post-operative MRI were collected. RESULTS collected 1021 glioblastoma, including 1008 IDHwt patients. 744 glioblastomas treated radiochemotherapy EORTC 26981/22981 (TMZ/RT→TMZ) following surgery. Among such homogenously patients, lower absolute volumes (in cm3) favorably associated outcome: ‘maximal CE resection’ (class 2) had superior outcome compared ‘submaximal 3) or ‘biopsy’ 4) (median OS: 19 versus 15 10 months; p=0.001). Extensive (≤ 5 cm3 tumor) provided an additional benefit complete resection, thus defining class 1 (‘supramaximal resection’) 24 p=0.008). value classes retained on multivariate analysis when adjusting molecular markers MGMT promotor status. Relative reduction percentage) not analysis, inter-rater agreement sufficient. CONCLUSION “RANO categories glioblastoma” are highly may serve stratification Removal beyond borders benefit, providing rationale explicitly denominate ‘supramaximal resection’.