- Additionally, patients must be at least 6 weeks from nitrosoureas, 4 weeks from temozolomide or carboplatin, 3 weeks from procarbazine, and 2 weeks from last vincristine administration. Patients must be at least 4 weeks from other cytotoxic therapies not listed above and 2 weeks for non-cytotoxic agents (e.g., interferon, tamoxifen).