DISEASE CHARACTERISTICS: Adenocarcinoma of the prostate treated by radical prostatectomy within the past 3 months Considered to be at high risk for recurrence as defined by at least 1 of the following characteristics on the radical prostatectomy specimen: Positive seminal vesicles Gleason 6 and preoperative PSA greater than 18 ng/mL Gleason 7 and preoperative PSA greater than 14 ng/mL Gleason 8, 9, or 10 and any preoperative PSA Undetectable PSA (i.e., less than 0.1 ng/mL) within 3 months following radical prostatectomy and at time of enrollment Negative lymph nodes at time of radical prostatectomy if lymphadenectomy performed Extracapsular penetration and/or positive surgical margins allowed