Tributyrin in Treating Patients With Refractory Prostate Cancer or Other Solid Tumors

DISEASE CHARACTERISTICS: * Histologically proven prostate cancer or other solid tumor that is refractory to standard treatment or for which no standard therapy exists * Patients with prostate cancer must meet the following conditions: * Stage D2 disease * Disease progression after orchiectomy or treatment with leuprolide or flutamide * If no prior orchiectomy, must continue leuprolide or other antiandrogen throughout study * No CNS neoplasms or brain metastases PATIENT CHARACTERISTICS: * Age: 18 and over * Performance status: ECOG 0-2 * Life expectancy: More than 3 months * WBC at least 3,000/mm3 * Platelet count at least 100,000/mm3 * Hemoglobin at least 9 g/dL * Bilirubin no greater than 1.5 mg/dL * AST and ALT no greater than 1.5 times normal * Creatinine no greater than 1.5 mg/dL OR creatinine clearance greater than 50 mL/min * No concurrent medical or psychiatric condition that would preclude study * Able to swallow numerous capsules * Willing to participate in pharmacokinetic studies * Not pregnant or nursing * Negative pregnancy test * Fertile patients must use effective contraception PRIOR CONCURRENT THERAPY: * At least 4 weeks since prior chemotherapy (more than 8 weeks since prior carmustine, mitomycin, or other drugs with delayed toxic effects) and recovered * No prior suramin * At least 4 weeks since prior flutamide * No concurrent hydrocortisone or other steroids * At least 4 weeks since prior radiotherapy and recovered * No concurrent palliative radi…