Introduction

This plenary session aimed to review the best contemporary methods of prostate biopsy in terms of approach (transrectal vs transperineal) and imaging-guidance modality (MRI and micro-ultrasound). The panelists discussing the approaches were Drs. Arvin George (transrectal approach) and Ben Ristau (transperineal approach), whereas Drs. Kristen Scarpato (MRI) and Samir Taneja (micro-ultrasound) discussed image-guidance modalities.

Transrectal vs Transperineal Approach

Several facets were considered when comparing prostate biopsy approaches, including cancer detection rates, pain scores, adverse events, and cost. Dr. George presented data from MUSIC (Michigan Urological Surgery Improvement Collaborative) on almost 10,000 men, showing similar cancer detection rates in both approaches (57.3% transperineally vs 56.5% transrectally, p=0.6). Similarly, 2 other randomized studies were presented that showed no difference in cancer detection rates, specifically 47% vs 53% in 339 men and 35% vs 32% in 200 men for transperineal and transrectal approaches, respectively (p >0.05).^1,2 However, the transperineal approach was superior for detection of apical disease in one study, where 16.2% vs 12% (p=0.046) of “anterior only” tumors were diagnosed transperineally compared to transrectal ­biopsies.³

More data from the MUSIC collaborative on adverse events suggested that there were no differences between biopsy approaches in emergency room visits within 30 days of biopsy, episodes of urinary retention, or hematuria. More importantly, hospitalization rates for infectious complications were 0.6% and 0.33% for transrectal and transperineal biopsies, respectively (p=0.11). The argument favoring the transperineal approach was bolstered by studies showing infectious complications of <1% and the possibility of doing biopsies without antibiotics, furthering the goal of antibiotic stewardship.^4,5 The counter-argument, however, was that infection risk is comparably low in transrectal biopsies when preventive measures, such as enhanced antibiotic prophylaxis, pre-biopsy rectal swab cultures to look for quinolone resistance, and formalin-dipping the needle between biopsies.

Regarding patient experience, data from Michigan and others suggest that overall pain and patient discomfort are higher with the transperineal approach, mainly driven by the discomfort associated with anesthetic administration. Dr. Ristau also highlighted that the addition of pudendal nerve blockade to the standard periprostatic block improves pain control in transperineal biopsies. Lastly, the transperineal approach is proposed to have higher costs relative to transrectal biopsies that are chiefly associated with capital costs and disposables (eg needle guide).

MRI and Micro-Ultrasound

The potential of pre-biopsy MRI to enhance detection of clinically significant cancer and to avoid over-detection and overtreatment of low-risk disease were underscored by Dr. Scarpato. Whereas transrectal-ultrasound are useful for template biopsies, areas of suspicion can be identified on MRI. Using the latest iteration of Prostate Imaging–Reporting and Data System^® (PI-RADS^®), version 2.1 simplifies interpretation and reporting of MRI imaging to enhance the detection of significant cancer (grade group ≥2). The key findings of clinical trials comparing MRI and transrectal ultrasound guidance were emphasized by Dr. Scarpato, particularly that MRI detects higher-grade lesions (30%), fewer low-grade cancers (17%), and could avoid biopsy in a third of men when negative.^6,7 Therefore, these data solidify the role of MRI as an intermediate step between PSA testing and prostate biopsy.

Dr. Taneja highlighted the need for alternative diagnostic options to MRI that stems from the variability in MRI quality, access to MRI, and the significant expenses associated with it. As such, micro-ultrasound is sought after as an alternative that is less costly and more accessible. Micro-ultrasound operates at 300% higher frequency than conventional ultrasound (17–29 vs 6–12 MHz), allowing for better resolution than conventional ultrasound. Micro-ultrasound can be used with or without MRI fusion and in both the transperineal and transrectal approach.

The panelists then discussed the Prostate Risk Identification using Micro-Ultrasound (PRI-MUS™), a validated 5-level risk scale that uses textural patterns to predict the likelihood of cancer. This scoring system has been shown to have a reasonable learning curve (40–60 cases) and to perform similarly to PI-RADS. Studies have demonstrated that in some instances where the MRI is negative in patients with significant cancer, a subset will have an abnormal PRI-MUS score. Moreover, PRI-MUS was also shown to have higher sensitivity (99.7% vs 84.3%) and negative predictive value (99.2% vs 64.5%) than PI-RADS. Lastly, the role of micro-ultrasound was emphasized in improving fusion biopsies as it improves lesion resolution and visual targeting of significant disease.^8,9 Taken together, compared to MRI, micro-ultrasound has similar diagnostic accuracy, short learning curve, lower overall cost, and ultimately returns the diagnostic workup back to the hands of the urologist.

Table. Upcoming randomized controlled trials comparing transrectal and transperineal prostate biopsy

Take Home Message

William Kissick first described the iron triangle of health in 1994, consisting of 3 competing elements of health care: access, quality, and costs. In keeping with these fundamentals, the transperineal approach may have better quality with lower sepsis rates than transrectal biopsies, but access and higher costs related to startup, disposables, and sedation (if performed in the operating room) should be considered. Whether the lower sepsis rate is enough to justify cost and patient discomfort, remains to be answered by the 2 randomized trials that aim to compare these approaches (see Table). Until then, given the limited availability of transperineal biopsy, a risk-stratified approach may be warranted.

In terms of image guidance, it is evident that the experience of radiologists is critical to the quality of MRI, and it is only cost-effective when the biopsy is omitted if the scan is negative. However, since 15% of clinically significant cancers are not seen on MRI, urologists need to use caution about using MRI to avoid biopsy. The potential benefit of micro-ultrasound can only be realized if it can substitute MRI rather than act as an adjunct and further increase costs. Currently, the Optimization of Prostate Biopsy-Micro-Ultrasound Versus MRI (OPTIMUM Study), which aims to compare 3 biopsy techniques in a multicenter randomized controlled trial (NCT05220501) is now open, with the primary and secondary endpoints being detecting clinically significant cancer in micro-ultrasound vs MRI-ultrasound fusion biopsy and micro-ultrasound/MRI fusion vs MRI-ultrasound fusion, respectively. We hope that the findings of these upcoming trials will improve the quality of prostate biopsy and enable us to direct appropriate efforts in providing accessible and cost-effective care for our patients.