 4. Patients must have recovered from the toxic effects of prior therapy: 4 weeks from any investigational agent, 4 weeks from prior cytotoxic therapy andor at least two weeks from vincristine, 4 weeks from nitrosoureas, 3 weeks from procarbazine administration, and 1 week for non-cytotoxic agents, e.g., interferon, tamoxifen, thalidomide, cis-retinoic acid, etc. radiosensitizer does not count. Any questions related to the definition of non-cytotoxic agents should be directed to the Principal Investigator. With regard to previous RT, there must be at least 6 months from the completion of RT or radiosurgery. 