PRIOR CONCURRENT THERAPY: Biologic therapy: Not specified Chemotherapy: At least 3 weeks since prior chemotherapy and recovered No more than 1 prior chemotherapy regimen allowed (either single or combination cytotoxic drug therapy) No prior 6-hydroxymethylacylfulvene No prior chemotherapy for other malignancy Endocrine therapy: Not specified Radiotherapy: At least 3 weeks since prior radiotherapy and recovered No prior radiotherapy for other malignancy Surgery: At least 3 weeks since prior surgery and recovered