Comparative effectiveness of radiotherapy with vs. without temozolomide in older patients with glioblastoma.

It is unknown whether the addition of temozolomide (TMZ) to radiotherapy (RT) is associated with improved overall survival (OS) among older glioblastoma patients. We performed a retrospective cohort SEER-Medicare analysis of 1652 patients aged ≥65 years with glioblastoma who received ≥10 fractions of RT from 2005 to 2009, or from 1995 to 1999 before TMZ was available. Three cohorts were assembled based on diagnosis year and treatment initiated within 60 days of diagnosis: (1) 2005-2009 and TMZ/RT, (2) 2005-2009 and RT only, or (3) 1995-1999 and RT only. Associations with OS were estimated using Cox proportional hazards models and propensity score analyses; OS was calculated starting 60 days after diagnosis. Pre-specified sensitivity analyses were performed among patients who received long-course RT (≥27 fractions). Median survival estimates were 7.4 (IQR, 3.3-14.7) months for TMZ/RT, 5.9 (IQR, 2.6-12.1) months for RT alone in 2005-2009, and 5.6 (IQR, 2.7-9.6) months for RT alone in 1995-1999. OS at 2 years was 10.1 % for TMZ/RT, 7.1 % for RT in 2005-2009, and 4.7 % for RT in 1995-1999. Adjusted models suggested decreased mortality risk for TMZ/RT compared to RT in 2005-2009 (AHR, 0.86; 95 % CI, 0.76-0.98) and RT in 1995-1999 (AHR, 0.71; 95 % CI, 0.57-0.90). Among patients from 2005 to 2009 who received long-course RT, however, the addition of TMZ did not significantly improve survival (AHR, 0.91; 95 % CI, 0.80-1.04). In summary, among a large cohort of older glioblastoma patients treated in a real-world setting, the addition of TMZ to RT was associated with a small survival gain.