Glioblastoma and increased survival with longer chemotherapy duration.
e13006 Background: The 5-year survival for patients (pts) with glioblastoma (GBM) is low at approximately 3%. Radiotherapy plus concomitant and adjuvant temozolomide (TMZ) remain the standard of care. The optimal duration of therapy with TMZ is unknown, though treatment periods of 6 months (mo), 12 mo and longer have been utilized. Whether or not there is a benefit with longer treatment duration is controversial. Methods: A retrospective chart review of all pts diagnosed with GBM who were treated at a regional referral center was conducted with data obtained from their electronic medical records. These pts were treated with TMZ for up to 2 years between January 1, 2002 and December 31, 2011. Survival was calculated as the time from initial surgical diagnosis until death. The Kaplan-Meier method with log-rank test was used to estimate the progression-free survival (PFS) as well as the overall survival (OS) distribution of pts after treatment. The results were compared to historical controls and data from previous clinical trials of pts treated up to 1 year. Results: Data from 56 pts were evaluated, the majority of whom had gross total resection and had external pathology review confirming the diagnosis of GBM. The OS probability was 55.4% (SE = 0.068) at 1 year, 26.9% (SE = 0.067) at 2 years and 20.1% (SE = 0.065) at 3 years. The median PFS time in this study group was 8 mo (95% CI = 4.0 – 9.0 mo). The probability of no progression at 2 years was 8.6% (SE = 0.05). Seven pts (12.5%) were treated with TMZ for 2 years. The probability of disease progression at 2 years among these pts was 33.3% with a median time-to-progression of 20 mo (95% CI = 5.0-28.0). These patients showed an increased survival probability at 3 years compared to pts who did not receive the 2 year treatment of TMZ (log-rank test Chi-square = 12.4, p = 0.0004). Conclusions: This analysis suggests that there may be an advantage for a longer duration of TMZ therapy in pts with GBM. In this review, treatment with TMZ for 2 years was associated with an increased survival benefit. While we consider the sample size to be too small for generalization, a prospective/multicenter study with a larger sample size might better evaluate the question of duration of TMZ therapy, particularly if both clinical and basic science data are paired.