Impact of extent of resection of glioblastoma multiforme (GBM) in the era of chemoradiation

Abstract

e13029 Background: Controversy remains regarding the impact of the extent of resection (EOR) on survival in patients with GBM (Sanai 2008). The main reason for this is the fact that most studies were based on the surgeon's estimate of the EOR, which is known to be unreliable, rather than early postoperative MRI scans (po-MRI). Data for the current standard of postoperative chemo-radiotherapy (CTRT) have recently been reported, but suffer from the same limitation (Gorlia 2008). We studied the prognostic impact of the EOR using early (<72 hours) po-MRI scans in a cohort of GBM patients treated with CTRT in a single center. Methods: The results of 48 consecutive patients (35 male, 13 female; age 18–73 yrs) treated with surgery, followed by concurrent CTRT (60 Gy plus temozolomide) and adjuvant temozolomide were assessed with respect to survival and relapse patterns. EOR was determined by both the surgeon's estimation and early po-MRI scans that were available in all but two patients. EOR was categorized as biopsy (N = 3), partial resection (N = 24), major resection (N = 11; i.e., total resection according to the surgeon's report, but residual tumor on po-MRI), and total resection (N = 10; i.e. no residual tumor on po-MRI). Results: Median overall survival of the entire cohort was 18.9 months, and EOR was the only significant prognostic factor (p = 0.02) on multivariate analysis, which also included age, gender, performance, and radiotherapy target volume. 2-year survival rates improved significantly with increasing EOR, with 0%, 18.9%, 68.6%, and 100% for biopsy, partial-, major-, and total resection, respectively. In-field progression was the predominant pattern of failure in 27 out of 30 patients (90%) with a recurrence. Time to neurological progression (TNP) was significantly correlated with EOR (p < 0.001). Median TNP was 3.0 months for biopsy, 7.0 months for partial resection, 20.5 months for major resection, and was not reached for total resection. Conclusions: With the use of more effective local therapy in the form of surgery and CTRT, the prognostic impact of the EOR on survival appears to be higher than previously reported. This should be accounted for in future trials. No significant financial relationships to disclose.