AT-08 * RADIOTHERAPY WITH VS WITHOUT TEMOZOLOMIDE IN OLDER PATIENTS WITH GLIOBLASTOMA

Abstract

BACKGROUND: A randomized trial of glioblastoma patients aged ≤70 years demonstrated that adding temozolomide (TMZ) to radiotherapy (RT) improved overall survival (OS). We examined whether adding TMZ to RT was associated with improved OS in older glioblastoma patients. METHODS: We performed a retrospective cohort study of 1,718 Medicare beneficiaries aged ≥65 years with glioblastoma diagnosed in a SEER region who received ≥10 daily fractions of RT between 2005-2009, or between 1995-1999 before TMZ was available. Patients were categorized into 3 cohorts based on diagnosis year and treatment received within 3 months of diagnosis: 1) 2005-2009 and TMZ/RT, 2) 2005-2009 and RT only, or 3) 1995-1999 and RT only. Associations between treatment group and OS were compared using Cox proportional hazards models and propensity score analyses, controlling for baseline patient characteristics. RESULTS: Median survival estimates were 9.4 (IQR, 5.2-17.0) months for TMZ/RT, 7.9 (IQR, 4.7-15.0) months for RT in 2005-2009, and 7.7 (IQR, 4.9-11.8) months for RT in 1995-1999. Two-year survival probabilities were 12.4% for TMZ/RT, 7.6% for RT in 2005-2009, and 3.3% for RT in 1995-1999. Propensity score-adjusted models showed decreased mortality risk for TMZ/RT compared to RT in 2005-2009 (AHR, 0.88; 95% CI, 0.79-0.98) and to RT in 1995-1999 (AHR, 0.70; 95% CI, 95% CI, 0.56-0.87). Subgroup and sensitivity analyses showed no significant advantage to TMZ/RT compared to RT in 2005-2009 among patients receiving long-course RT (≥27 fractions; AHR, 0.89; 95% CI, 0.79-1.01). CONCLUSIONS: Concurrent TMZ was associated with a small survival benefit among older glioblastoma patients receiving RT, but no significant survival benefit was observed among patients who received standard long-course RT.