The impact of primary Gleason grade on biochemical outcome following brachytherapy for Gleason score 7 prostate cancer

Abstract

4699 Background: Although the perception exists that biochemical outcome in Gleason score 7 patients with dominant pattern 4 histology is inferior to Gleason 3+4 patients, conflicting conclusions have been reported for both radical prostatectomy. In this study, we evaluate the effect of the dominant histologic pattern in Gleason score 7 prostate cancer on biochemical progression-free survival following permanent prostate brachytherapy. Methods: Between April 1995 and October 2001, 273 consecutive hormone naïve patients underwent permanent interstitial brachytherapy for clinical T1c-T3a NxM0 (2002 AJCC) prostate cancer. No patient underwent seminal vesicle biopsy or pathologic lymph node staging. All patients underwent brachytherapy more than 3 years prior to analysis. The median follow-up was 4.4 years. Biochemical progression-free survival was defined by a PSA cutpoint ≤ 0.4 ng/mL after nadir or by the ASTRO consensus definition. Clinical, treatment and dosimetric parameters evaluated for biochemical progression-free survival included primary Gleason grade, clinical T-stage, pretreatment PSA, risk group, percent positive biopsies, perineural invasion, patient age, isotope, supplemental XRT, prostate volume, brachytherapy planning volume, the percent of the target volume receiving 100%, 150%, and 200% of the prescribed dose (V100/150/200), the minimum percent of the prescribed dose covering 90% of the target volume (D90), tobacco consumption, hypertension and diabetes. Results: The actuarial 8-year biochemical progression-free survival rate was 94.1% and 94.3% using a PSA cutpoint ≤ 0.4 ng/mL after nadir and the ASTRO consensus definition, respectively and a median posttreatment PSA of < 0.1 ng/mL. When stratified by the dominant histologic pattern, no statistical difference in outcome was noted for any of the evaluated parameters. Only pretreatment PSA and percent positive biopsies were statistically significant predictors of biochemical outcome. Conclusions: In hormone naïve Gleason score 7 patients, prostate brachytherapy results in a high probability of 8-year biochemical progression-free survival and is independent of Gleason 3+4 versus 4+3 histology. No significant financial relationships to disclose.