 - Patients who have had chemotherapy or radiotherapy within 4 weeks 6 weeks for nitrosoureas or mitomycin C prior to entering the study or those who have not recovered to grade 1 treatment-limiting toxicity levels for adverse events due to agents administered more than 4 weeks earlier; exception: patients may have received palliative low dose radiotherapy to the limbs 1-4 weeks before this therapy, provided pelvis, ribs, sternum, scapulae, vertebrae, or skull were not included in the radiotherapy field 