Perineural invasion is not predictive of biochemical outcome following prostate brachytherapy

PURPOSE The purpose of this article is to evaluate whether the presence of perineur al invasion (PNI) in the biopsy specimen is predictive of 5-year biochemica l disease-free outcome after prostate brachy-therapy. MATERIALS AND METHODS Four hundred twenty-five patients underwent transperineal ultrasound-guided prostate brachytherapy using either Pd-103 or I-125 for clinical T1b/T3a N XMO (1997 American Joint Committee on Cancer) adenocarcinoma of the prostat e gland from April 1995 to October 1999. No patient was lost to follow-up, and no patient underwent pathological lymph node staging. Two hundred twent y-one patients were implanted with 103Pd, and 204 patients were implanted w ith I-125. Of this cohort, 190 patients were implanted without supplemental beam radiation, and 235 received moderate-dose external-beam radiation the rapy followed by a prostate brachytherapy boost. One hundred sixty-three pa tients received hormonal manipulation in conjunction with the brachytherapy implant (86 of these patients received moderate-dose external-beam radiati on therapy before brachytherapy), and 262 patients were hormone naive. Peri neural invasion, defined as carcinoma tracking along or around a nerve with in the perineural space, was identified in 105 patients (24.7% of the popul ation). The median patient age was 68 years (range, 48-81 years). The mean follow-up was 37.1 +/- 15.2 months, and the median followup was 35.4 months (range, 6-74 months). Follow-up was calculated from the date of implantati on. Biochemical disease-freesurvival was defined by the American Society of Therapeutic Radiation and Oncology (ASTRO) consensus definition. RESULTS When Kaplan-Meier survival analysis was performed, the presence of PNI did not predict failure. When PN1 was entered into a Cox regression analysis wi th evaluated clinical predictors of failure (age, clinical T stage, pretrea tment prostate-specific antigen level, and Gleason score) or treatment para meters (use of neoadjuvant hormonal therapy, supplemental external-beam rad iation therapy, and choice of isotope), PNI did not add to the predictive s trength of these variables. The median disease-free prostate-specific antig en level was 0.1 ng/mL for the entire cohort. CONCLUSIONS Our results indicate that actuarial 5-year biochemical outcomes with a pros tate brachytherapy approach that utilizes generous periprostatic margins is not dependent on the presence of PNI. ln addition, PNI should not be used as an independent prognosticator in determining the need for combined-modal ity therapy in patients undergoing prostate brachytherapy.