NCOG-19. FUNCTIONAL OUTCOME AFTER RE-RESECTION OF TUMOR PROGRESSION, MIXED LESION OR TREATMENT-ASSOCIATED EFFECTS IN IRRADIATED DIFFUSE GLIOMAS (GRADE 2-4): IDENTIFYING CLINICAL AND RADIOLOGICAL DETERMINANTS

Abstract In cases of radiological progression in patients with irradiated diffuse gliomas, recurrence-resection is frequently performed. In our previous histological evaluation 19% of these re-resection cases were found to be due to treatment-associated effects (TAE). Limited literature substantiating which patients will benefit from surgery and which patients will deteriorate postoperatively is available. We aim to (a) describe the functional outcomes after re-resection of an irradiated diffuse glioma in adult patients; (b) compare early functional outcomes between patients with TAE versus progressive disease; (c) identify predictors of early functional outcome. In this single-center, retrospective, cohort study, we included consecutive adult patients with diffuse glioma who underwent first-line radiotherapy and, upon radiological progression, a re-resection. Re-resection tissue was classified histologically (based on mitosis presence/absence) and by the multidisciplinary tumor board as tumor progression, TAE or mixed lesion. The primary endpoint was the functional outcome 30 days postoperatively, expressed as the Karnofsky Performance Scale (KPS). Univariable and multivariable logistic regression were used to identify clinicoradiological predictors of KPS deterioration of any severity. Of 159 included patients, 41 (25.8%) experienced mild KPS deterioration (10 points) and 25 (15.9%) a clinically relevant KPS deterioration (20 or more). KPS improvement (10 points or more) occurred in 31 patients (19.4%). Histological diagnosis groups did not differ significantly in KPS outcome. Pre-operative steroid usage (any dose) was an independent predictor of KPS deterioration (OR 2.46, 95%CI 1.12-5.39, p=0.025). Analysis of pre-operative radiological determinants is in progress. In conclusion, in this large single-center cohort of diffuse gliomas undergoing re-resection with systematic clinical evaluation, clinically relevant deterioration after re-resection occurred in 15.9% of all patients. Risk of deterioration is comparable in all histological diagnosis groups. Pre-operative steroid usage was identified as predictor for deterioration (of any severity). These results may provide clinical guidance in identifying which patients will benefit from re-resection.