# Positive Margin Location and Prostate Biopsy Route: A Consecutive Cohort Comparison of Transperineal and Transrectal Techniques

## TL;DR

This study compares transperineal and transrectal prostate biopsy techniques and finds no difference in cancer spread at the surgical edge after prostate removal.

## Contribution

The study provides evidence that transperineal biopsy does not increase the risk of positive surgical margins compared to transrectal biopsy.

## Key findings

- Overall positive surgical margin rates were similar between transperineal and transrectal biopsy methods.
- Transperineal biopsy did not increase the risk of positive margins at the apex of the prostate.
- Adjusting for various factors showed no association between biopsy technique and margin risk.

## Abstract

Transperineal (TP) prostate biopsy is increasingly used because it lowers infection risk and improves sampling of certain regions of the prostate compared with the traditional transrectal (TR) approach. However, concerns have been raised that TP biopsy might cause more scarring near the apex of the prostate, potentially increasing the chance of leaving microscopic cancer at the edge of the specimen during subsequent prostate removal surgery (radical prostatectomy), known as a positive surgical margin. In our study of over 1000 men during the transition from TR to TP biopsy, 260 went on to have surgery. We found no difference between the two biopsy methods in overall positive surgical margin rates or in specific margin locations. After adjusting for tumour features and surgical factors, biopsy technique was not associated with margin risk, supporting the oncologic safety of the transperineal approach.

Background: Transperineal (TP) prostate biopsy is increasingly used due to its superior infectious safety and enhanced sampling of anterior and apical prostate regions. Concerns have been raised that TP biopsy may induce greater post-biopsy fibrosis, particularly at the apex, potentially increasing positive surgical margin (PSM) rates at radical prostatectomy (RP). We evaluated whether biopsy technique influences overall or location-specific PSMs at RP. Methods: We performed a retrospective comparative cohort study of 1027 consecutive men who underwent TR biopsy and TP biopsy at our institution as we transitioned from TR to TP diagnostic technique. Patients from this cohort who were subsequently diagnosed with clinically localised prostate cancer and underwent RP were analysed. Clinical, biopsy, and pathological data were collected; all Gleason scores were standardised to Prognostic Grade Groups. PSMs were defined as tumour at the inked margin and categorised as apical, lateroposterior, or basal. Associations between biopsy technique and PSM outcomes were analysed using uni- and multivariable logistic regression. Results: Among 1027 biopsies, 260 men proceeded to RP, including 114 following TP biopsy and 146 following TR biopsy. Baseline pathological characteristics were similar between groups. Overall PSM rates did not differ between TP and TR cohorts (38.6 percent vs. 41.8 percent, p = 0.604). Margin location was also comparable at the apex (11.9 percent vs. 13.5 percent), lateroposterior (5.4 percent vs. 10.8 percent), and base (4.2 percent vs. 5.8 percent) respectively. In adjusted analyses controlling for age, PSA, grade, tumour stage, nodal status, and surgical approach, biopsy technique was not associated with overall PSMs (OR 0.70; 95 percent CI 0.39–1.24; p = 0.22) or with any location-specific PSMs. Conclusions: TP biopsy did not increase the risk of positive surgical margins at radical prostatectomy, either overall or at the apex. These findings do not support concerns that TP biopsy disrupts apical tissue planes or compromises oncologic outcomes. The results reinforce the safety of TP biopsy as a contemporary diagnostic standard, while highlighting the need for larger prospective studies to confirm these observations.