DISEASE CHARACTERISTICS: Histologically confirmed primary or metastatic malignancy refractory to standard therapy or for which no curative therapy exists No progressive metastatic disease requiring palliative therapy within 4 weeks of study Progressive disease Increase in preexisting lesions on imaging or physical examination Patients with sole progression criterion of increased biochemical marker (e.g., carcinoembryonic antigen or CA 15-3) or increased symptoms not eligible Prostate cancer must be either progressive metastatic disease on imaging studies or have rising PSA values Minimum of 3 rising PSA values obtained at least 1 week apart, or 2 rising PSA values more than 1 month apart, with at least a 25% overall increase Serum testosterone less than 50 ng/mL Must maintain castrate status No active CNS or epidural tumor