Inclusion Criteria

DISEASE CHARACTERISTICS:

- Histologically confirmed adenocarcinoma of the prostate meeting all of the following
criteria:

- Curatively treated with radical prostatectomy OR definitive radiotherapy

- No signs of clinical recurrence or dissemination of prostate cancer by digital
rectal examination without tumor

- No local recurrence by CT scan or MRI of the pelvis

- No metastases by bone scan and chest x-ray NOTE: Prior Prostascint scans allowed
regardless of results

- At least 3 prostate-specific antigen (PSA) measurements obtained over at least 90
days after radical prostatectomy on post-radiotherapy PSA nadir must be available

- PSA at least 2 ng/mL after prostatectomy OR at least 4 ng/mL after prior
radiotherapy

- Patients previously treated with radiotherapy must have a PSA clearly rising
from lowest value within 6 months after completion of therapy

PATIENT CHARACTERISTICS:

Age

- 18 and over

Performance status

- ECOG 0-1

Life expectancy

- At least 12 months

Hematopoietic

- Platelet count at least 100,000/mm^3

- Hemoglobin at least 10 g/dL

Hepatic

- Bilirubin no greater than upper limit of normal (ULN)

- Alkaline phosphatase no greater than 2 times ULN

Renal

- Creatinine less than 1.8 mg/dL

- Phosphorus normal

- No hypercalcemia (albumin-corrected calcium greater than ULN)

- No nephrolithiasis

- Single episode of renal lithiasis allowed provided episode occurred more than 5
years prior to study

Other

- Fertile patients must use effective double-barrier contraception for at least 1 week
before, during, and for at least 2 weeks after study

- No symptomatic pancreatitis

- No uncontrolled diabetes

- No known or suspected inability to comply with study requirements (e.g., abuse of
alcohol/drugs or psychotic states)

- Curatively treated condition associated with renal stones (e.g., hyperparathyroidism,
bladder dysfunction, or obstructive uropathy) allowed provided patient has been free
of stone formation for more than 5 years

PRIOR CONCURRENT THERAPY:

Biologic therapy

- Not specified

Chemotherapy

- No prior chemotherapy for prostate cancer

- At least 24 months since prior chemotherapy for other diseases

Endocrine therapy

- More than 6 months since prior hormonal therapy, including neoadjuvant or adjuvant
androgen deprivation therapy (e.g., luteinizing hormone-releasing hormone analogue or
antiandrogen)

- No prior androgen deprivation therapy of more than 8 months duration

- No prior hormonal therapy for prostate cancer more than 3 months after definitive
local therapy

- No concurrent androgen therapy

Radiotherapy

- See Disease Characteristics

- More than 3 months since prior radiotherapy for locally recurrent prostate cancer

- No concurrent radiotherapy, including for pain control

Surgery

- See Disease Characteristics

Other

- More than 4 weeks since prior investigational drugs

- No concurrent medication known to affect systemic calcium metabolism, including any
of the following:

- More than 400 IU of cholecalciferol supplements

- More than 500 IU of vitamin A supplements

- Calcium supplements

- Fluoride

- Antiepileptics