Temozolomide (TMZ), given concurrently with radiotherapy (RT) and as adjuvant monotherapy afterwards, has led to improved survival in glioblastoma multiforme (GBM). However, it is unclear whether its primary mechanism of action is through enhancement of radiation response, independent cytotoxicity, or both. We sought to determine the relative contribution of concomitant temozolomide in patients treated by concurrent and adjuvant TMZ versus adjuvant TMZ alone in the setting of newly diagnosed GBM.

We identified patients diagnosed with GBM and treated with surgery, involved-field radiotherapy, and chemotherapy at MGH between 2002 and 2004. Eligible patients received either adjuvant temozolomide alone (group 1) or temozolomide concurrently with RT followed by adjuvant TMZ (group 2). The primary endpoint of this retrospective analysis was overall survival (OS).

Forty-three patients (group 1, n = 21; group 2, n = 22) were included in this study. The median follow-up was 33.7 months for surviving patients. There were no significant differences in baseline characteristics between these two groups. On univariate analysis, patients who received concurrent and adjuvant temozolomide experienced a 2-year OS of 51% and median survival of 25.5 months, compared with a 2-year OS of 36% and median survival of 15.6 months for group 1 patients (P < 0.05). On multivariable analysis, the hazard ratio (HR) favoring concurrent TMZ trended towards significance (HR = 0.51, P = 0.08) despite modest patient numbers.

Concurrent and adjuvant TMZ was associated with improved survival compared to adjuvant TMZ alone, highlighting the potentiation of radiation effect by temozolomide in the clinical setting.