PRIOR CONCURRENT THERAPY: Biologic therapy: More than 4 weeks since immunotherapy Chemotherapy: Prior anthracyclines allowed provided no symptomatic heart disease is present More than 4 weeks since chemotherapy (at least 2 weeks, with recovery, if disease progression is documented) More than 6 weeks since nitrosoureas, melphalan, or mitomycin Endocrine therapy: More than 1 week since corticosteroids (except physiological doses for respiratory ailments or adrenal insufficiency) Radiotherapy: More than 4 weeks since radiotherapy (at least 2 weeks, with recovery, if disease progression is documented) Surgery: More than 3 weeks since major surgery (excluding surgery for tumor collection)