Carbon Ion Radiotherapy for Primary Glioblastoma

Overview

Treatment standard for patients with primary glioblastoma (GBM) is combined radiochemotherapy with temozolomide (TMZ). Radiation is delivered up to a total dose of 60 Gy using photons. Using this treatment regimen, overall survival could be extended significantly however, median overall survival is still only about 15 months. Carbon ions offer physical and biological advantages. Due to their inverted dose profile and the high local dose deposition within the Bragg peak precise dose application and sparing of normal tissue is possible. Moreover, in comparison to photons, carbon ions offer an increase relative biological effectiveness (RBE), which can be calculated between 2 and 5 depending on the GBM cell line as well as the endpoint analyzed. Protons, however, offer an RBE which is comparable to photons. First Japanese Data on the evaluation of carbon ion radiation therapy showed promising results in a small and heterogeneous patient collective. In the current Phase II-CLEOPATRA-Study a carbon ion boost will be compared to a proton boost applied to the macroscopic tumor after surgery at primary diagnosis in patients with GBM applied after standard radiochemotherapy with TMZ up to 50 Gy. In the experimental arm, a carbon ion boost will be applied to the macroscopic tumor up to a total dose of 18 Gy E in 6 fractions at a single dose of 3 Gy E. In the standard arm, a proton boost will be applied up to a total dose 10 Gy E in 5 single fractions of 2 Gy E. Primary endpoint is overall survival, secondary objectives are progression-free survival, toxicity and safety.

Study design The purpose of the trial is to compare a carbon ion boost to a proton boost delivered to the macroscopic tumor in combination with combined radiochemotherapy with TMZ in patients with primary GBM. The aim of the study is to compare overall survival as a primary endpoint, and progression free survival, toxicity and safety as secondary endpoints. Focus of the analysis is to evaluate the change in overall survival and local control by carbon ion radiotherapy. Therefore, the aim of the trial is to evaluate the improvement in outcome due to effect of the altered biology of carbon ions on GBM. Chemotherapy with TMZ is considered standard treatment and is administered continuously as it would be applied in standard patient care outside any trial. Trial Design The trial will be performed as a single-center two-armed randomized Phase II study. Patients fulfilling the inclusion criteria will be randomized into two arms: Arm A - Experimental Arm Carbon Ion Radiation Therapy as a Boost to the macroscopic tumor Total Dose 18 Gy E, 6 fractions, 3 Gy E single dose Arm B - Standard Arm Proton Radiation Therapy as a Boost to the macroscopic tumor Total Dose 10 Gy E, 5 fractions, 2 Gy E single dose Standard chemotherapy with TMZ will be continued during the experimental and standard arm in conventional dosing of 75 mg/m2 per day.