DISEASE CHARACTERISTICS: Histologically proven locally confined adenocarcinoma of the prostate Stage I or II (T1b-c or T2a-b, NX, M0) PSA no greater than 10 ng/mL Prostate volume by transurethral ultrasound no greater than 45/mm3 at least 1 week, but no more than 4 weeks, prior to implant Gleason score no greater than 6 American Urological Association voiding symptom score no greater than 12 No evidence of distant metastases No lymph node involvement