PRIOR CONCURRENT THERAPY: Biologic therapy: Not specified Chemotherapy: See Disease Characteristics No prior SPI-77 At least 3 weeks since other prior chemotherapy (6 weeks for nitrosoureas, mitomycin, or suramin) No concurrent antineoplastic agents Endocrine therapy: No concurrent hormonal anticancer therapy Radiotherapy: At least 2 weeks since prior radiotherapy No concurrent radiotherapy Surgery: At least 2 weeks since prior major surgery for cancer Other: At least 30 days since other prior investigational agent No other concurrent investigational agents