Vaccine Therapy Plus QS21 in Treating Patients With Prostate Cancer

DISEASE CHARACTERISTICS: Histologically confirmed prostate cancer Disease progression after primary surgery (radical prostatectomy) or radiotherapy with or without prior neoadjuvant androgen ablation Minimum of 3 rising PSA values, taken at least 2 weeks apart, with more than a 50% rise in PSA level above the baseline value (1.0 ng/mL post -prostatectomy or 2.0 ng/mL post-radiotherapy) Received prior intermittent hormonal therapy after prior primary therapy Non-castrate levels of testosterone (more than 50 ng/mL) Evaluable disease (by serial changes in PSA) No radiographic evidence of metastatic disease No active CNS or epidural tumor No soft tissue and/or bone disease No androgen-independence with no evidence of radiographic disease May not be symptomatic or anticipated to develop symptoms within 6 months of study entry PATIENT CHARACTERISTICS: Age: 18 and over Performance status: Karnofsky 70-100% Life expectancy: At least 6 months Hematopoietic: WBC at least 3,500/mm^3 Platelet count at least 100,000/mm^3 Hepatic: Bilirubin less than 2.0 mg/dL SGOT less than 3 times upper limit of normal Renal: Creatinine no greater than 2.0 mg/dL OR Creatinine clearance at least 40 mL/min Cardiovascular: No clinically significant cardiac disease (New York Heart Association class III or IV) Pulmonary: No severe debilitating pulmonary disease Other: No allergy to seafood (shellfish) No other active malignancy within the past 5 years except nonmelanoma skin cancer No infection requiring antibiotics No narcotic-dependent pain No positive stool guaiac unless associated with hemorrhoids or prior documented radiation-induced proctitis PRIOR CONCURRENT THERAPY: Biologic therapy: Not specified Chemotherapy: At least 4 weeks since prior chemotherapy Endocrine therapy: See Disease Characteristics See Chemotherapy At least 2 weeks since change in hormonal therapy (e.g., prednisone or dexamethasone) except to maintain castrate levels of testosterone Radiotherapy: See Disease Characteristics At least 4 weeks since prior radiotherapy No concurrent irradiation of only measurable lesion Surgery: See Disease Characteristics No concurrent surgery of only measurable lesion Other: Recovered from prior therapy At least 8 weeks since prior suramin and/or documented plasma concentration of suramin if less than 50 micrograms/mL (replacement hydrocortisone allowed) No other concurrent oncolytic agents No concurrent immunosuppressive therapy