Clinical significance of quantification of perineural cancer invasion on MRI-targeted prostate biopsy.

[BACKGROUND] MRI-targeted biopsy (T-Bx) has considerably improved the detection of clinically significant prostate cancer, while the clinical impact of perineural invasion (PNI) seen on T-Bx remains unclear. We aimed to determine the prognostic significance of PNI quantification on T-Bx.

[METHODS] We assessed 169 consecutive patients undergoing T-Bx, along with systematic biopsy, and subsequent radical prostatectomy by quantifying actual PNI foci on T-Bx and comparing their postoperative oncologic outcomes.

[RESULTS] No PNI was detected on T-Bx in 136 (80.5%) cases, whereas 1 (n = 18; 10.7%), 2 (n = 7; 4.1%), 3 (n = 5; 3.0%), and 4 (n = 3; 1.8%) foci of PNI were present on T-Bx of the remaining cases. Compared to cases with no PNI, those exhibiting single PNI had significantly higher pT stage and significantly higher incidence of lymph node metastasis. However, there were no significant differences in any of the clinicopathologic features examined, including tumor grade, stage, and volume, between cases with single vs. multifocal PNI. Univariate survival analysis revealed a significantly higher risk of biochemical recurrence following prostatectomy in patients with PNI (vs. no PNI; P < 0.001) or multifocal PNI (vs. single PNI; P = 0.043) on T-Bx. Differences in recurrence-free survival between 0 vs. 1 PNI (P = 0.176), 1 vs. 2 PNI (P = 0.187), and 2 vs. 3-4 PNI (P = 0.939) were not statistically significant. In multivariable analyses, multifocal PNI (vs. single PNI) on T-Bx showed significance for the risk of postoperative recurrence (hazard ratio 4.922 or 6.173, P < 0.05).

[CONCLUSIONS] Multifocal PNI on T-Bx was found to be associated with significantly poorer oncologic outcomes, as an independent predictor, in men with prostate cancer undergoing radical prostatectomy. PNI quantification on T-Bx may thus provide useful information for the more accurate risk stratification of prostate cancer.