Inclusion Criteria

DISEASE CHARACTERISTICS:

- Diagnosis of prostate cancer

- Clinical stage cT1-2-3a, N0, M0 disease pre-operatively

- Pre-operative PSA ≤ 5 x upper limit of normal

- Presenting the following conditions after radical prostatectomy:

- Gleason sum 5-10

- Pathologic stage pT2R1 (positive surgical margins with at least a tumor
trans-section > 2 mm) or pT3a-b (irrespective of margin status)

- Negative lymph node (LN) status (pN0) by LN sampling or LN dissection

- Unknown pathological LN status is not allowed, except for disease
classified as cT ≤ cT1c with baseline PSA ≤ 10 ng/mL, Gleason score < 7,
and ≥ 12 positive core biopsies < 50%

- Undetectable post-operative PSA within 3 months of surgery

PATIENT CHARACTERISTICS:

- WHO performance status 0-1

- WBC ≥ 3 x 10^9/L

- Hemoglobin ≥ 110 g/L

- Platelet count ≥ 100 x 10^9/L

- No other malignancy except adequately treated basal cell carcinoma of the skin or
other malignancy from which the patient has been disease free for at least 5 years

- No psychological, familial, sociological, or geographical condition potentially
hampering compliance with the study protocol and follow-up schedule

PRIOR CONCURRENT THERAPY:

- See Disease Characteristics

- More than 5 years since prior chemotherapy

- No prior pelvic irradiation

- No prior bilateral orchiectomy

- No prior hormonal treatment except neoadjuvant treatment lasting ≤ 3 months

- No other concurrent anticancer agent or modality