OBJECTIVES: I. Determine the antitumor activity of DX-8951f as measured by PSA response in patients with hormone refractory prostate cancer. II. Determine the antitumor activity of this drug in the subpopulation of these patients with measurable disease. III. Evaluate the quantitative and qualitative toxicities of this drug in these patients. IV. Evaluate the pharmacokinetics of this drug in these patients.