ROUTINE PROSTATE BIOPSIES FOLLOWING RADIOTHERAPY FOR PROSTATE-CANCER - RESULTS FOR 226 PATIENTS

Objectives. To determine the time course of histologic resolution of p rostate cancer following radiotherapy (RT) and to correlate biopsy res ults with clinical outcome. Methods. Since July 1990, all patients tre ated with radical external beam RT for prostate cancer at the General Division of the Ottawa Regional Cancer Centre have had systematic tran srectal ultrasound (TRUS) and TRUS-guided biopsies beginning 12 months after RT and then every 6 months until negative or until clinical fai lure. Thus, 226 patients have had 375 TRUS with four to seven specimen s per examination. Stage distribution was T1b: 32, T1c: 11, T2a: 45, T 2b: 82, T3: 50, and T4: 6. Median follow-up was 33 months. Results. Bi opsy results were negative in 69.5% of patients by 30 months of follow -up. Thirty-two (14%) had local failure (T1b: 12.5%, T1c: 0%, T2a: 11% , T2b: 15%, T3: 18%, T4: 33%). Seven (3%) had chemical failure, and 47 (21%) had biopsy-only failure. Median follow-up for the biopsy-only f ailure group is only 19.5 months and mean prostate-specific antigen (P SA) is 1.0 ng/mL. Thirty-nine patients, initially with biopsy-only fai lure, have converted to negative biopsies at a median of 26 months. Na dir PSA for patients with local failure was 3.9 ng/mL at 14 months ver sus 0.7 ng/mL at 23 months for those without failure. Patients with la te conversion to negative biopsy results had a later nadir PSA of 1.3 ng/mL at 27.3 months. Conclusions. Routine prostate biopsy specimens a fter RT in an unselected population show tumor clearance that is in ag reement with long-term clinical follow-up, although tumor may take mor e than 50 months to resolve. Nadir PSA can be used to predict outcome.