DISEASE CHARACTERISTICS: Histologically proven asymptomatic recurrent prostate cancer Prior local treatment status Curatively treated OR Locally advanced disease noncuratively treated with LHRH agonist therapy Currently receiving 1 line of hormonal therapy (with LHRH agonists or surgical castration) and failing treatment with rising PSA only Patients who received LHRH agonists instead of surgical castration continue to receive LHRH agonist during study Biochemical progression documented by 3 consecutively rising PSA measurements, each at least 2 weeks apart, with the last measurement being 50% or greater than the nadir PSA achieved after the last therapeutic maneuver (first line hormonal therapy as noted above) PSA (50% increased values) greater than 4 ng/mL for patients with intact prostates and greater than 0.8 ng/mL for post-prostatectomy patients Rising PSA for less than 10 months Castrate levels of testosterone (less than 30 ng/dL) No bone or visceral metastases by bone scan and CT scan of abdomen and pelvis (except localized abnormalities and pelvic lymph node and soft tissue disease) No CNS or leptomeningeal involvement

PATIENT CHARACTERISTICS: Age: 18 and over Performance status: Karnofsky 90-100% Life expectancy: Greater than 6 months Hematopoietic: WBC at least 3,000/mm3 Absolute neutrophil count at least 1,500/mm3 Hemoglobin at least 8.0 g/dL Platelet count at least 75,000/mm3 Hepatic: Liver function tests no greater than 2.5 times upper limit of normal (ULN) Renal: Creatinine no greater than 1.5 times ULN Cardiovascular: No New York Heart Association class III or IV heart disease with uncontrolled and/or unstable cardiac or coronary artery disease Other: No other malignancy within the past 5 years that would confound the etiology of metastatic disease except curatively treated nonmelanomatous skin cancer No other nonmalignant disease that would confound evaluation or preclude compliance Fertile patients must use effective contraception

PRIOR CONCURRENT THERAPY: Biologic therapy: No prior systemic biologic anticancer therapy Chemotherapy: No prior chemotherapy Concurrent chemotherapy such as estramustine containing regimens or mitoxantrone allowed at the discretion of the protocol investigator Endocrine therapy: See Disease Characteristics No prior systemic hormonal anticancer therapy except LHRH antagonists and/or nonsteroidal antiandrogens (e.g., flutamide, bicalutamide, or nilutamide) Concurrent aminoglutethimide, prednisone, or diethylstilbestrol or other estrogens allowed at the discretion of the protocol investigator Radiotherapy: At least 6 weeks since prior palliative radiotherapy Surgery: See Disease Characteristics Other: No other prior systemic anticancer therapy At least 4 weeks since other prior investigational drugs No other concurrent bisphosphonate agent