PRIOR CONCURRENT THERAPY: Biologic therapy: At least 1 month since prior interferon No prior hematopoietic growth factors or cytokines except epoetin alfa No concurrent epoetin alfa Chemotherapy: No prior topotecan No prior chemotherapy for this disease At least 12 months since prior chemotherapy for another disease No other concurrent chemotherapy Endocrine therapy: At least 1 month since prior corticosteroids No concurrent hormonal therapy for disease-related conditions Concurrent steroids for adrenal failure allowed No concurrent dexamethasone and other steroidal antiemetics Radiotherapy: No prior radiotherapy for this disease At least 12 months since prior radiotherapy for another disease Surgery: Not specified Other: No prior cytotoxic therapy (including low-dose antimetabolites) for this disease At least 1 month since prior retinoids