Risk Stratification by Quantification of Perineural Cancer Invasion on Prostate Needle Core Biopsy: Should It Be Counted?

We assessed the prognostic significance of quantification of perineural invasion on prostate biopsy.We quantified actual perineural invasion foci in the entire prostate biopsy specimens from 724 patients and compared corresponding radical prostatectomy findings and long-term oncologic outcomes.No perineural invasion was detected in 524 (72.4%) prostate biopsies, whereas 1 (n=129; 17.8%), 2 (n=40; 5.5%), 3 (n=18; 2.5%), 4 (n=7; 1.0%), and 5-10 (n=6; 0.8%) perineural invasion foci were present in other cases. We confirmed a higher risk of recurrence after radical prostatectomy in patients with perineural invasion on prostate biopsy than in those with no perineural invasion (P < .001). Remarkably, recurrence-free survival was comparable between those with 0 vs 1 perineural invasion (P = .9) or 2 vs ≥3 perineural invasions (P = .3). Nonetheless, multifocal perineural invasion per prostate biopsy (vs single perineural invasion; P < .001) and >1 perineural invasion per 10-mm tumor (vs ≤1 perineural invasion; P = .008) were associated with worse outcomes. Interestingly, in a subgroup outcome analysis of single vs multifocal perineural invasions per prostate biopsy, there was a significant difference in patients showing perineural invasion involving only 1 of the sextant sites. In multivariable analysis, both multifocal perineural invasion/case (HR=5.48, P < .001) and >1 perineural invasion/10-mm tumor (HR=3.96, P < .001) showed significance for recurrence. Meanwhile, compared with CAPRA (Cancer of the Prostate Risk Assessment) score alone (0.687/0.685), Harrell's C index/AUC for predicting 5-year recurrence-free survival was gradually increased when 1 (0.722/0.740), 2 (0.747/0.773), or 3 (0.760/0.792) point(s) were additionally assigned to multifocal perineural invasion.Multifocal perineural invasion and >1 perineural invasion per 10-mm tumor on each prostate biopsy were thus found to be associated with poorer prognosis, as independent predictors, in men with prostate cancer undergoing radical prostatectomy.