k) Patients must have recovered from the toxic effects of prior therapy: 2 weeks from any investigational agent, two weeks from vincristine, 6 weeks from nitrosoureas, 3 weeks from procarbazine, 1 week for non-cytotoxic agents, (e.g., interferon, tamoxifen, thalidomide, cis-retinoic acid, etc.), and 4 weeks from other cytotoxic therapy. Any questions related to the definition of non-cytotoxic agents should be directed to the Study Chair.