Retrospective comparison of standard and escalated doses of radiotherapy in newly diagnosed glioblastoma patients treated with concurrent and adjuvant temozolomide

ABSTRACT

BACKGROUND: To compare the efficacies of standard dose-(SDRT) and escalated dose radiotherapy (EDRT) in newly diagnosed glioblastoma (GBM) with concurrent and adjuvant temozolomide (TMZ). MATERIALS AND METHODS: Outcomes of 126 newly diagnosed GBM patients who received SDRT (60 Gy, 30 fractions) or EDRT (70 Gy, 30 fractions) with concurrent plus adjuvant TMZ were retrospectively analyzed. Both groups received concurrent TMZ (75 mg/m2) during the course of RT and at least one course of adjuvant TMZ (150–200 mg/m2), thereafter. Overall survival (OS) and local progression free survival (LPFS) constituted the primary and secondary endpoints, respectively. RESULTS: At median 14.2 months follow-up, 26 (20.6%) patients were alive. Median LPFS and OS were 9.2 [95% confidence interval (CI); 8.4–10.0] and 15.4 months (95% CI; 12.1–18.8), respectively, for the entire cohort. Although the median OS was numerically superior in the EDRT this difference could not reach statistical significance (22.0 vs. 14.9 months; P = 0.45), Likewise, LPFS was also (9.9 vs. 8.9 months; P = 0.89) not different between the two treatment groups. In multivariate analysis, better recursive partitioning analysis class (3–4 vs. 5; P = 0.044) and extensive surgery (gross total resection vs. subtotal resection/biopsy only; P= 0.021) were identified to associate significantly with superior OS times, irrespective of the RT protocol. CONCLUSIONS: Although the current median OS of 22 months of the EDRT group is promising, no statistically significant survival advantage for EDRT was observed even in the presence of TMZ. Randomized studies with larger population sizes and available genetic markers are warranted to conclude more reliably on the fate of EDRT plus TMZ.