Radiotherapy for localized prostate cancer: assessment of results by systematic biopsy and PSA

This study attempted to determine the failure pattern after radiotherapy for localized prostate cancer using systematic biopsies and serum PSA in assessment of outcome. Between July 1987 and February 1993, 226 patients treated with radical external beam radiotherapy were followed prospectively with systematic transrectal ultrasound-guided biopsies and serum PSA. Four hundred and ten transrectal ultrasound-guided biopsies were performed with 4-7 samples (usually six) per session. Stage distribution was T1b: 32, T1c: 11, T2a: 45, T2b: 62, T3: 50, T4: 6. Median follow-up was 41 months. The rate of positive biopsies continued to decrease over time, reaching a nadir of 30.5% at 30 months post radiotherapy. Local failures have occurred in 17% (38/226) overall, or 13% of T1b, 0% of T1c, 13% of T2a, 20% of T2b and 21% of T3-4. Six additional patients (2.5%) have had biochemical failure and 34 (15%) have biopsy-only failure. Forty seven patients initially showing residual tumor on post radiotherapy biopsies (median time 18 months), demonstrated late tumor clearance, achieving negative biopsies at a median time of 28 months. Median nadir PSA in patients with no evidence of disease (NED) at last follow-up was 0.5 ng/mL, achieved at 24 months post radiotherapy. For patients with delayed tumor clearance, the median nadir PSA was 0.6 ng.mL at 27 months. For those with local failure it was 1.6 ng.mL at 16 months and for all failures, 1.8 ng/mL at 13 months. Systematic prostate biopsies show that tumor clearance after radiotherapy may take up to 30 months. Histologic tumor clearance parallels the fall in serum PSA. Serum PSA nadirs earlier and at a higher value in patients destined to fail.