A phase I trial using the proteasome inhibitor bortezomib and concurrent temazolomide and radiotherapy for high grade gliomas

Abstract

2061 Background: Improving the response of patients with high-grade astrocytomas continues to remain a challenge despite advances in chemoradiation. Preclinical studies have demonstrated the importance of the NF-kappaB pathway treatment resistance and enhancement of radiosensitivity by proteasome inhibition. This open-label, phase I study evaluated the safety of 3 dose levels (0.7, 1.0, 1.3 mg/m2/dose) of intravenously administered bortezomib, a reversible proteasome inhibitor with unique properties in combination with chemoradiation. Methods: Eligible patients had a diagnosis of high-grade glioma. Other requirements included performance status 0–1 and adequate hematologic reserve. Previous radiotherapy and/or chemotherapy was allowed. Patients received fraction sizes of XRT that ranged from 1.8–3.5 Gy/day for total doses between 35–66 Gy. During radiotherapy, temozolomide was administered continuously at a daily dose of 75 mg/m2. The starting dose level of bortezomib was 0.7 mg/m2/ days 1, 4, 8, 11 of 21-day cycle for up to 2 cycles. This was followed by 1.0 mg/m2 and 1.3 mg/m2 dose levels. The primary endpoint of the study was dose-limiting toxicity (DLT), defined as any Grade 4–5 toxicity or Grade 3 toxicity(ies) requiring hospitalization and/or XRT interruption. Response was also assessed (1-month post-XRT brain MRI). Results: A total of 27 patients were enrolled. There were no DLTs observed in any dose groups. Grade 1 and 2 toxicities consisted of stomatitis, erythema, and alopecia. Of 24 patients evaluable for response, 1 patient had no evidence of disease, 3 patients had a PR; 9 patients had stable disease and 11 patients had progressive disease. Conclusions: Bortezomib can be combined at full dose with concurrent temozolomide and radiation therapy with minimal adverse effects. Correlative translational endpoints are still pending. The results observed justify further evaluation in a phase II setting. [Table: see text]