DISEASE CHARACTERISTICS:

* Histologically confirmed stage T1-T3 adenocarcinoma of the prostate before radical prostatectomy and lymph node dissection

* Must have undergone prostatectomy within the past 120 days
* Must meet at least 1 of the following pathologic criteria:

* Gleason sum at least 8
* pT3b (seminal vesicle), pT4, or N1
* Gleason sum of 7 and positive margin
* Preoperative PSA greater than 15 ng/mL, Gleason score greater than 7, or PSA level greater than 10 ng/mL and Gleason score greater than 6
* Must have an undetectable PSA (no greater than 0.2 ng/mL) documented after surgery or prior to adjuvant hormonal therapy (for patients initiating adjuvant hormonal therapy prior to study)
* No evidence of metastatic disease on bone scan if PSA is 20 ng/mL or greater at clinical diagnosis
* No distant metastatic disease

PATIENT CHARACTERISTICS:

Performance status:

* SWOG 0-1

Life expectancy:

* Not specified

Hematopoietic:

* Not specified

Hepatic:

* Not specified

Renal:

* Not specified

Cardiovascular:

* No uncontrolled congestive heart failure
* If history of cardiac disease, LVEF at least 50% by MUGA scan or 2-D echocardiogram

Other:

* No HIV positivity
* No other prior malignancy within the past 5 years except adequately treated basal cell or squamous cell skin cancer or stage I or II cancer that is currently in complete remission

PRIOR CONCURRENT THERAPY:

Biologic therapy:

* Not specified

Chemotherapy:

* Not specified

Endocrine therapy:

* Prior neoadjuvant hormonal therapy of no more than 4 months duration before radical prostatectomy allowed
* Other concurrent adjuvant hormonal therapy allowed if initiated prior to study
* Concurrent low-dose megestrol (less than 40 mg/day) for hot flashes allowed

Radiotherapy:

* No prior radiotherapy
* No concurrent whole pelvis irradiation
* Concurrent radiotherapy allowed at the discretion of the physician

Surgery:

* See Disease Characteristics
* See Endocrine therapy
* Recovered from prior surgery

Other:

* No other prior or concurrent therapy for adenocarcinoma of the prostate