PP71. CLINICAL OUTCOMES FOR GLIOBLASTOMA PATIENTS WITH SOLITARY, MULTIFOCAL AND MULTICENTRIC DISEASE

Abstract

INTRODUCTION: Based on imaging features, glioblastoma (GBM) can be classified as solitary, multifocal or multicentric. The incidence of multifocal/multicentric GBM has been reported to range from 0.5 to 35% and some studies have reported poorer survival in patients with multiple lesions. Two potential reasons have been proposed: (1) intrinsic differences in tumour biology; (2) failure to encompass the entire tumour within the radiotherapy planning tumour volume. To address this question we investigated clinical, imaging and genetic features in a cohort of GBM patients. METHODS: Imaging, clinical, treatment, MGMT methylation and outcome data were collected retrospectively from consecutive GBM patients treated in a single cancer centre between January 2011 and June 2012. Tumours were categorised as solitary, multifocal or multicentric by a consultant neuroradiologist. RESULTS: 122 patents with GBM were identified. Median age was 60 and male:female ratio was 2.1:1. MGMT promoter status was unmethylated in 48% of tumours, methylated in 37% and unknown in 15%. Preoperative imaging modality was CT in 70% and MRI in 30% of patients. Overall, the proportion of patients with solitary, multifocal and multicentric tumours was 78%, 15.5% and 6.5 % respectively, but in patients undergoing MR imaging these proportions were 60%, 26.5% and 13.5%. Gross total resection was performed in 65% of solitary compared with 42% of multifocal and 25% of multicentric cases, and radical chemoradiation was delivered to 50% of solitary, 58% of multifocal and 12% of multicentric cases. Overall, median survival was increased in solitary compared with multifocal/multicentric patients (9.9 vs. 6.7 months, p = 0.046). In patients receiving radical chemoradiation, however, there was no difference in overall survival between solitary and multifocal/multicentric patients (18.5 vs. 16.8 months, p=0.57). MGMT promoter methylation was associated with increased survival in patients with solitary tumours (14.6 vs. 8.5 months, p= 0.014) but not multifocal/multicentric tumours (3.8 vs. 6.9 months, p= 0.3). CONCLUSION: In this retrospective study the incidence of multifocal/multicentric GBM was in line with previous studies. Pre-operative CT imaging may underestimate the incidence of multifocal/multicentric disease. Our main finding was that multifocality or multicentricity did not affect survival in patients to whom radical chemo-radiotherapy could be delivered.