10. Patients must have recovered from the toxic effects of prior therapy, and there must be a minimum time of: 1) 28 days from the administration of any investigational agent. 2) 28 days from administration of prior cytotoxic therapy with the following exceptions: (a) 14 days from administration of vincristine. (b) 42 days from administration of nitrosoureas. (c) 21 days from administration of procarbazine.