RADIOTHERAPY FOR SUPRATENTORIAL LOW-GRADE GLIOMAS - RESULTS AND PROGNOSTIC FACTORS WITH SPECIAL FOCUS ON TUMOR VOLUME PARAMETERS

From 1973 to 1990, 67 patients with a diagnosis of low-grade glioma we re treated in our hospital. Overall survival was analysed as well as t he influence of patient, tumour- and treatment-related factors with sp ecial focus on tumour volume parameters. Our study group included 49 p atients treated by surgery and post-operative radiotherapy (RT) (40 pa tients) or post-biopsy irradiation alone (9 patients). Total or almost total resection was performed in 16 patients; partial excision was do ne in 24. With the available pre-surgery and pre-RT CT-scan and/or MRI images we were able to calculate tumour volumes by measuring the larg est tumour dimensions in the three axes D1, D2, D3 and by assuming an ellipsoidal growth (i.e., tumour volume = D1D2D3pi/6). RT was delivere d to involved regions: either the residual tumour volume or the tumour bed. The median RT dose was 56 Gy (45-60, range). The 60- and 90-mont h overall survival (Kaplan-Meier) was 79% and 67%, respectively. Femal e sex, > 70% Karnofsky (Kf) score, oligodendroglioma and < 71 cm3 (alm ost-equal-to 5 cm diameter sphere) tumour residuals before RT were ass ociated with better overall survival rates (p < 0.05, log-rank). Howev er, a Cox proportional hazards model showed that only the histological subtype and Kf significantly determined the patients' outcome: 60-mon th overall survival of 100%, 62%, 83% and 64% for oligodendrogliomas, mixed oligo-astrocytomas and grade-I and grade-II astrocytomas, respec tively. The primary tumour volume did not predict survival. Small resi dual tumour volumes before RT were, however, associated with a better outcome, although they were strongly related with the more favorable o ligodendroglioma histologic subtype. Non-pilocytic astrocytomas and mi xed tumors did not show a significant volume-outcome relationship in o ur study.