PRIOR CONCURRENT THERAPY: Biologic therapy: Not specified Chemotherapy: At least 4 weeks since prior antineoplastic chemotherapy unless unequivocal evidence of tumor progression No concurrent systemic chemotherapy Endocrine therapy: Corticosteroids allowed if at lowest possible dose and stable for at least 10 days prior to entry Radiotherapy: At least 3 months since prior radiotherapy to site of measurable disease unless unequivocal evidence of disease progression Surgery: Not specified