Patients must have clinically progressive disease documented prior to entry. Progression must be documented by at least one of the following parameters: two consecutively rising tumor marker levels, and/or at least one new metastatic deposit on Tc-99 bone scintigraphy, and/or progression of soft tissue metastases as measured by appropriate modalities (i.e., imaging, palpation), and/or development of new area of malignant disease (measurable or evaluable).