Patterns of care and outcomes of chemoradiation versus radiation alone for MGMT promoter unmethylated glioblastoma.

OBJECTIVE: The recommended treatment for O6 -methylguanine-DNA methyltransferase (MGMT) promoter unmethylated glioblastoma (GBM) is radiation therapy with concurrent/adjuvant temozolomide (TMZ). However, it is well known that the clinical benefit from TMZ is lower in these patients. We sought to analyze patterns of care and outcomes of chemoradiation versus radiation alone in this cohort using a large, hospital database.

PATIENTS AND METHODS: Patients diagnosed with MGMT promoter unmethylated GBM from 2010 to 2012 who received radiation (RT) or chemoradiation (CRT) were identified in the National Cancer Database. Logistic regression was performed to assess for predictors of receiving chemoradiation. The Kaplan-Meier method was used to assess overall survival (OS) by treatment group and Cox regression analysis was used to assess impact of covariates on OS.

RESULTS: There were 738 patients who met the study criteria, of which 107 (14.5%) received RT alone and 631 (85.5%) received CRT with median RT dose 6000cGy for both groups. Median follow up for living patients was 21.9 months. Ninety-two (12.5%) patients did not undergo any resection, 330 (44.7%) underwent a subtotal resection and 316 (42.8%) had a gross total resection. The median and 2-year OS was 16.8 months and 24.7% for RT alone compared to 15.6 months and 25.9% for the CRT group (p = 0.250). On multivariable analysis, the addition of chemotherapy had no impact on survival (HR 1.12, 95% CI 0.86-1.46, p = 0.396).

CONCLUSION: Despite the routine use of chemoradiation among patients with MGMT promoter unmethylated GBM, there does not appear to be a survival benefit compared to radiation alone.