PRIOR CONCURRENT THERAPY: Biologic therapy: At least 4 weeks since prior immunotherapy Chemotherapy: At least 4 weeks since prior chemotherapy (6 weeks for nitrosoureas, mitomycin, and high dose carboplatin) No other concurrent antitumor drugs Endocrine therapy: No concurrent corticosteroids Radiotherapy: At least 4 weeks since prior radiotherapy (6 weeks for extensive radiotherapy) No concurrent radiotherapy Surgery: Not specified Other: No prior anthracyclines or anthracenediones No other concurrent investigational drugs