Final report of a phase I/II trial of hyperfractionated and accelerated hyperfractionated radiation therapy with carmustine for adults with supratentorial malignant gliomas. Radiation Therapy Oncology Group Study 83-02.

BACKGROUND: Efforts to improve local control and survival by increasing the dose of once-daily radiation therapy beyond 70 Gray (Gy) for patients with malignant gliomas has yet been unsuccessful. Hyperfractionated radiation therapy (HF) should allow for delivery of a higher total dose without increasing normal tissue late effects, whereas accelerated hyperfractionated radiation therapy (AHF) may minimize tumor repopulation by shortening overall treatment time. The Radiation Therapy Oncology Group (RTOG) conducted a randomized Phase I/II study of escalating doses of HF and AHF either carmustine (bis-chlorethyl nitrosourea [BCNU]) fro adults with supratentorial glioblastoma multiforme (GBM) or anaplastic astrocytoma (AA). Primary study endpoints were overall survival and acute and chronic treatment-related toxicity.

METHODS: From 1983 to 1989, 786 patients with supratentorial gliomas (81% with GBM and 19% with AA) were stratified by histology, age, and performance status and randomized to receive partial brain irradiation, utilizing either HF (1.2 Gy twice daily to doses of 64.8, 72, 76.8, or 81.6 Gy) of AHF (1.6 Gy twice daily to doses of 48 or 54.4 Gy). All patients received carmustine. The distinction of pronistic factors was similar on all arms.

RESULTS: There were 747 eligible and analyzable patients among 786 enrolled patients (95%). Two patients had a Grade 5 and 65 patients had a Grade 4 chemotherapy toxicity. Two patients in the 81.6 Gy arm experienced late Grade 4 radiation toxicity and there was 1 late radiation-associated death in the 54.4 Gy arm. The rate of Grade 3 of worse radiation toxicity at 5 years, calculated by the delivered does level, was 3% in the lowest total dose arms (48 and 54.4 Gy), 4% in the intermediate dose arms (64.8 and 72 Gy), and 5% in the highest dose arms (76.8 and 81.6 Gy) (p = 0.54). Survival rates at 2 and 5 years were: 21% and 11%, and 4%, respectively, for GBM patients. There were no significant differences between the treatment arms with regard to median survival time (MST), when analyzed by the originally assigned dose. The MST for all patients varied between 10.8 months and 12.7 months (P = 0.59); between 9.6 months and 11 months for patients with GBM (P = 0.43); and between 30.4 months and 85.8 months for patients with AA (P = 0.78). Analysis of the survival rates for all patients by dose received rather than by dose assigned revealed a 14% 5-year survival rate for the lower HF doses (64.8 and 73 Gy), 11% for the higher doses (76.8 and 81.6 Gy), and 10% for the AHF doses (48 and 54.4 Gy) (P = 0.1). The subgroup a AA patients had a better MST (49.9 months) in the lower received HF doses than in the higher HF doses (34.6 months) (P = 0.35). In contrast, GM patients who received the higher HF doses had survival superior to the patients in the AHF arms (MST of 11.6 months and 10.2 months, respectively, P = 0.04).

CONCLUSIONS: The use of HF with BCNU and dose escalation up to 81.6 Gy is both feasible and tolerable, although late toxicity increases slightly with increasing dose. The best MST with the least toxicity were observed for AA in the lower received HF doses (72 and 64.8 Gy). Accordingly, 72 Gy in two 1.2 Gy fractions was used as the investigational arm of a completed Phase III trial (RTOG 90-06). In contrast, for GBM patients, longer survival times were noted in the higher received HF doses (78.6 and 81.6 Gy), suggesting the role for further dose escalation. The low toxicity rate with AHF arms suggest that further dose escalation is possible and is currently occurring in RTOG 94-11.