Perineural Invasion Predicts Increased Recurrence, Metastasis, and Death From Prostate Cancer Following Treatment With Dose-Escalated Radiation Therapy

Purpose To assess the prognostic value of perineural invasion (PNI) for patients treated with dose-escalated external-beam radiation therapy for prostate cancer. Methods and Materials Outcomes were analyzed for 651 men treated for prostate cancer with EBRT to a minimum dose ≥75 Gy. We assessed the impact of PNI as well as pretreatment and treatment-related factors on freedom from biochemical failure (FFBF), freedom from metastasis (FFM), cause-specific survival (CSS), and overall survival. Results PNI was present in 34% of specimens at biopsy and was significantly associated with higher Gleason score (GS), T stage, and prostate-specific antigen level. On univariate and multivariate analysis, the presence of PNI was associated with worse FFBF (hazard ratio = 1.7, p < 0.006), FFM (hazard ratio = 1.8, p < 0.03), and CSS (HR = 1.4, p < 0.05) compared with absence of PNI; there was no difference in overall survival. Seven-year rates of FFBF, FFM, and CCS were 64% vs. 80%, 84% vs. 92%, and 91% vs. 95% for those patients with and without PNI, respectively. On recursive partitioning analysis, PNI predicted for worse FFM and CSS in patients with GS 8–10, with FFM of 67% vs. 89% ( p < 0.02), and CSS of 69% vs. 91%, ( p < 0.04) at 7 years for those with and without PNI, respectively. Conclusions The presence of PNI in the prostate biopsy predicts worse clinical outcome for patients treated with dose-escalated external-beam radiation therapy. Particularly in patients with GS 8–10 disease, the presence of PNI suggests an increased risk of metastasis and prostate cancer death.