HIGH-DOSE CONFORMAL RADIOTHERAPY INFLUENCED THE PATTERN OF FAILURE BUT DID NOT IMPROVE SURVIVAL IN GLIOBLASTOMA-MULTIFORME

Background and Purpose: Although glioblastoma multiforme is clearly ra diation-resistant, there is evidence of a dose-dependent response rela tionship. The purpose of the study was to evaluate the impact of highe r dose by rotational multileaf collimator (MCL) conformal radiation th erapy. Materials and Methods: From 1984 to 1995, 38 consecutive cases with intracranial glioblastoma multiforme mere treated using the rotat ional MLC conformal therapy. There were 25 men and 13 women with a med ian age of 47 years (12-73 years, mean 46.5 years), Median Karnofsky p erformance score was 80 (30-100, mean 78.2). Median tumor volume was 6 4 cc (8-800 cc, mean 110.3 cc). All underwent surgical intervention (o nly biopsy in 1, partial resection in 13, subtotal resection in 21, an d gross total resection in 3). Radiation dose to was 60 to 80 Gy (medi an 68.5 Gy, mean 68.3 Gy) in 21 patients treated before 1990 and 90 Gy in the 17 patients thereafter. Biweekly i.v. chemotherapy was also ad ministered for both arms. Results: The I-year, 2-year, 5-year, and 10- year overall survival rates were 75%, 42%, 20%, and 15%, respectively. Univariate analysis showed the initial tumor volume, residual tumor v olume, and Karnofsky performance score were statistically significant factors for survival. Only the residual tumor volume was statistically significant by multivariate analysis. The 5-year survival rate of pat ients with residual tumors of 5 cc or less in volume was as good as 37 %. Survival of the 90-Gy Group appeared inferior to that of the Low-Do se Group, though no statistical difference was seen (the 3-year surviv al was 40% vs. 22%). Local failure was observed in 16 of the 19 recurr ences in the Low-Dose Group, whereas it was observed in only 4 of the 13 recurrences in the 90-Gy Group. The difference in pattern of failur e was statistically significant. Two patients of the High-Dose Group d eveloped radiation necrosis and one died of it. Conclusions: The high- dose conformal radiotherapy did not improve survival in the disease, b ut did change the pattern of failure. (C) 1998 Elsevier Science Inc.