Benefit of adjuvant radiation therapy for localized prostate cancer with apositive surgical margin

Purpose: Positive surgical margins are common after radical prostatectomy, and the role of adjuvant therapy in such cases is controversial. We determi ned the benefit of postoperative external beam radiation therapy in patient s with margin positive prostate cancer with respect to biochemical progress ion or cancer recurrence. To decrease confounding factors that may affect t he likelihood of biochemical progression our study was limited to men with organ confined cancer and a single positive margin. Materials and Methods: We retrospectively evaluated the records of a nested matched cohort of 76 patients with pathological stage T2N0 prostate cancer and a single positive margin who underwent adjuvant radiation therapy with in 3 months of radical prostatectomy. There was a positive margin at the pr ostatic apex in 35 cases, prostatic base in 18, posterior prostate in 11, u rethra in 7, and prostatic apex and urethra in 5. These patients were match ed 1:1 with 76 controls who did not receive adjuvant radiation therapy. Nei ther group received androgen deprivation therapy. Patients and controls wer e matched exactly for the margin positive site, age at surgery, preoperativ e serum prostate specific antigen, Gleason score and DNA ploidy. Biochemica l relapse was defined as posttreatment PSA greater than 0.2 ng./ml. Results: Overall there was significant estimated improvement plus or minus standard error in 5-year clinical and biochemical progression-free survival in 88% +/- 5% versus 59% +/- 11% of patients treated with adjuvant radiati on therapy versus no radiation therapy (p = 0.005). No patient who received radiation therapy had local or distant recurrence, while 16% of controls h ad recurrence (p = 0.015). When stratified by site of margin positivity, th e 5-year estimated clinical and biochemical progression-free rate in 18 cas es and controls with a positive base margin was 95% +/- 15% and 65% +/- 13% respectively (p = 0.02). The rate in 35 cases and cases with a positive ap ex margin was 95% +/- 5% and 64% +/- 15%, respectively (p = 0.07). Limited sample size precluded analysis of the other sites. Conclusions: Patients with localized prostate cancer and a singe positive s urgical margin appear to have a lower rate of biochemical relapse at 5 year s when adjuvant radiation therapy is administered. Defmitive evidence of th e beneficial effect of adjuvant radiation therapy for patients with involve d surgical margins awaits conclusion of randomized clinical trials.