Purpose: We assessed the prognostic significance of quantification of perineural invasion on prostate biopsy.
Materials and methods: 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.
Results: 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.
Conclusions: 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.
Keywords: biopsy, needle; paraneoplastic syndromes, nervous system; prognosis; prostatectomy; prostatic neoplasms.