Olaparib, Temozolomide, and Concomitant Radiotherapy for Partially Resected or Biopsy-Only Glioblastoma First-Line Treatment: Results from the OLA-TMZ-RTE-01 Phase I Study

Abstract

Purpose: Radiochemotherapy remains the mainstay of glioblastoma (GBM) first-line treatment after extended surgery, but the prognosis is still poor. PARP inhibitors like olaparib may improve GBM outcomes. We implemented a phase I to IIa trial to assess the safety and efficacy of olaparib combined with standard radiochemotherapy as a first-line treatment in patients with unresected GBM. We herein present results of phase I.

Patients and methods: Based on the Stupp regimen, two sequential dose escalations of olaparib were performed to distinguish the radiotherapy period and the maintenance period for assessing the MTD of olaparib separately for each treatment period. Dose escalations were performed by a Time-to-Event Continual Reassessment Method.

Results: A total of 30 patients were enrolled: 20 (66.7%) men, median age 59 years (range, 25-70), and 12 patients (42.9%) with Eastern Cooperative Oncology Group performance status of 0. Among them, 16 and 11 patients were assessable for determining MTD in each period. Hematologic dose-limiting toxicities were experienced by four and one patients in each sequential dose escalation, respectively. The MTD was olaparib 100 mg twice daily for 3 days a week in concomitant during both the radiochemotherapy and maintenance periods of the standard treatment. The median progression-free and overall survival were 6.2 and 19.8 months, respectively. The 2-year survival rate was 36.7% (22.9-58.7).

Conclusions: Intermittent dosing of olaparib at radiosensitizing concentrations in concomitant with the Stupp protocol has an acceptable safety profile with promising outcomes in patients with unresectable GBM. Further efficacy determination is ongoing in the phase IIa step.