PRIOR CONCURRENT THERAPY: Biologic therapy: At least 30 days since prior cytokines and recovered No more than 1 prior treatment with cytokines (interleukin-2 or interferons) Chemotherapy: No prior cytotoxic chemotherapy No prior aminocamptothecin No other concurrent antineoplastic agents Endocrine therapy: At least 30 days since prior hormone therapy and recovered No more than 1 prior hormone therapy (tamoxifen or medroxyprogesterone) Radiotherapy: Prior radiotherapy allowed if indicator lesion and greater than 15% of marrow producing bone have not been irradiated Surgery: Recovered from prior surgery Other: At least 30 days since other investigational agents No concurrent investigational agents