Phase I Study of Topotecan Plus Cranial Radiation for Glioblastoma Multiforme: Results of Radiation Therapy Oncology Group Trial 9507

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Abstract
PURPOSE: A phase I trial was conducted by the Radiation Therapy Oncology Group (RTOG) to determine the maximum-tolerated dose of topotecan that could be safely combined with standard cranial radiation for glioblastoma multiforme. A secondary objective was to document the acute and late toxicities of this combination of chemotherapy and radiation. PATIENTS AND METHODS: Forty-seven patients with histologically confirmed glioblastoma multiforme were entered onto this phase I trial. Three cycles of topotecan were administered at 21-day intervals commencing at day 1 of cranial radiotherapy (60 Gy/30 fractions). Each cycle consisted of daily 30-minute intravenous (IV) infusions for 5 days. The dose of topotecan was escalated in three-dose increments from 0.5 mg/m2/d to 1.0 mg/m2/d to 1.5 mg/m2/d in different patient groups. RESULTS: The majority of patients were over age 50. Three dose levels of topotecan were tested. Fifteen patients accrued to level 1 (topotecan dose 0.5 mg/m2/d). No grade 4 toxicities were seen. Sixteen patients accrued to level 2 (topotecan dose 1.0 mg/m2/d), five of whom had brief episodes of grade 4 neutropenia. Seventeen patients accrued to level 3 (1.5 mg/m2/d). Six of these patients had brief episodes of grade 4 neutropenia and four developed grade 3 thrombocytopenia. No serious nonhematologic or late toxicities were seen. Median survival for all patients was 9.7 months. There was no apparent difference in survival by topotecan dose schedule. CONCLUSION: Toxicity was acceptable at an IV topotecan dose of 1.5 mg/m2/d administered daily for 5 days every 21 days for three cycles. A phase II trial has been performed using this dose of topotecan.

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