Etanidazole as a modulator of combined modality therapy in the rat 9l-gliosarcoma

The use of chemotherapy has led to improved treatment outcome for some pediatric patients with medulloblastoma. We have used a pre-radiation chemotherapy regimen consisting of vincristine and CDDP. The 9L gliosarcoma implanted intracranially and subcutaneously in the same animals was used as a preclinical model system to assess the efficacy of treatment combinations including: vincristine, CDDP, cyclo-phosphamide, etanidazole and radiation. The experimental endpoints were percent increase-in-lifespan, tumor growth delay and tumor cell survival. Both the tumor growth delay and percent increase-in-lifespan improved as the number of agents included in the chemotherapy regimen increased. so that the chemotherapy regimen including all four agents (ETA/VIN/CDDP/CTX) resulted in the greatest tumor growth delay (23.6 +/- 1.5 days) and the greatest increase-in-lifespan (35.8%). When radiation (20 Gray, single dose) was added to the treatment regimens the combinations of ETA/CTX/X-ray and ETA/VIN/CDDP/CTX/X-ray resulted in equivalent tumor growth delays (25.2 +/- 1.3 days and 25.8 +/- 1.7 days, respectively), while the greatest increase-in-lifespan (39.1%) was obtained with the five agent combination. The response of the 9L gliosarcoma to CDDP and cyclophosphamide over a dosage range was very similar to that of the murine FSaII fibrosarcoma. Our results indicate that etanidazole may be an effective chemosensitizer of combination chemotherapy and combined modality treatment regimens for brain tumors.