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

PATIENT CHARACTERISTICS: Age: 18 and over Performance status: Karnofsky 70-100% Life expectancy: Not specified Hematopoietic: WBC at least 3,500/mm3

Platelet count at least 100,000/mm3 Hepatic: Bilirubin no greater than 1.0 mg/dL AST no greater than 37 U/L PT no greater than 14 seconds Renal:

Creatinine no greater than 2.0 mg/dL Cardiovascular: No significant cardiac disease No New York Heart Association class III or IV heart disease Pulmonary: No severe debilitating pulmonary disease Other: No infection requiring IV antibiotic treatment No other severe medical problems that would preclude study Not pregnant or nursing Negative pregnancy test Fertile patients must use effective contraception

PRIOR CONCURRENT THERAPY: Biologic therapy: Recovered from prior biologic therapy Chemotherapy: At least 4 weeks since prior chemotherapy and recovered Endocrine therapy: Recovered from prior endocrine therapy Radiotherapy: At least 4 weeks since prior radiotherapy and recovered No concurrent radiotherapy to target lesions Surgery: Not specified Other: At least 4 weeks since other prior investigational anticancer drugs and recovered No concurrent ketoconazole in patients with prostate cancer