DISEASE CHARACTERISTICS: Histologically confirmed prostate cancer No radiographic evidence of metastatic disease Must show signs of disease progression 3 or more rising PSA values documented, taken at no less than weekly intervals, to greater than 50% above baseline PSA PSA at least 1.0 ng/mL (post prostatectomy) OR 2.0 ng/mL (post radiation) Evaluable disease by serial changes in PSA Progression after primary therapy to include surgery or radiotherapy (with or without neoadjuvant androgen ablation), or intermittent hormonal therapy with noncastrate levels of testosterone (greater than 50 ng/mL) allowed No soft tissue and/or bone disease or androgen independent disease with no evidence of radiographic disease No symptomatic disease or anticipated to be symptomatic within 6 months No active CNS or epidural tumor

PATIENT CHARACTERISTICS: Age: 18 and over Performance status: Karnofsky 70-100% Life expectancy: At least 6 months Hematopoietic: WBC at least 3,500/mm3 Platelet count at least 100,000/mm3 Hepatic: Bilirubin less than 2.0 mg/dL OR 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 New York Heart Association class III-IV heart disease Pulmonary: No severe debilitating pulmonary disease Other: No other malignancy within past 5 years except nonmelanoma skin cancer No concurrent infection requiring antibiotics No narcotic dependent pain No positive stool guaiac excluding hemorrhoids No history of documented radiation induced proctitis No allergy to seafood

PRIOR CONCURRENT THERAPY: Biologic therapy: No prior murine monoclonal antibody therapy No other concurrent immunotherapy Chemotherapy: At least 4 weeks since prior chemotherapy and recovered No concurrent chemotherapy Endocrine therapy: See Disease Characteristics At least 2 weeks since prior changes in hormonal therapy including prednisone or dexamethasone At least 8 weeks since prior suramin OR documented plasma concentration less than 50 mg/mL (replacement doses of hydrocortisone allowed) Radiotherapy: See Disease Characteristics At least 4 weeks since prior radiotherapy and recovered No concurrent radiotherapy to only measurable lesion Surgery: See Disease Characteristics No concurrent surgery Other: No other concurrent anticancer agents