A Model to Predict the Feasibility of Concurrent Chemoradiotherapy With Temozolomide in Glioblastoma Multiforme Patients Over Age 65

Objectives: It is controversial whether concurrent chemoradiotherapy (CRT) with temozolomide is feasible and beneficial in elderly patients with glioblastoma. Materials and Methods: Retrospective analysis of 74 elderly glioblastoma patients (65 y and above) treated with concurrent CRT with temozolomide. Factors influencing prognosis and feasibility of CRT were investigated. Results: The median overall survival was 11.3 months. Univariate analysis showed a significant difference in median overall survival for cumulative dose of concurrent temozolomide (optimal cutoff, 2655 mg/m2; 13.9 mo for >2655 mg/m2 vs. 4.9 mo for ≤2655 mg/m2; P=0.0216, adjusted for multiple testing). Furthermore, cumulative dose of concurrent temozolomide >2655 mg/m2 was a significant independent prognostic parameter in multivariate analysis (hazard ratio, 0.33; P=0.002). Hematotoxicity was the most common cause of treatment interruption or discontinuation in patients with an insufficient cumulative temozolomide dose. Prognostic factors for successful performance of CRT with a cumulative dose of concurrent temozolomide >2655 mg/m2 were female sex (odds ratio [OR], 0.174; P=0.006), age (OR, 0.826 per year; P=0.017), and pretreatment platelet count (OR, 1.013 per 1000 platelets/µL; P=0.001). For easy clinical application of the model an online calculator was developed, which is available at http://www.OldTMZ.com . Conclusions: The probability of successful performance of concurrent CRT with temozolomide can be estimated based on the patient's age, sex, and pretreatment platelet count using the model developed in this study. Thus, a subgroup of elderly glioblastoma patients suitable for chemoradiation with temozolomide can be identified.

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