Prostate cancer is the most common non-cutaneous cancer in American men. In 2023, the American Cancer Society predicts that there will be 288,300 new cases of prostate cancer and 34,700 men will die of prostate cancer. While the incidence of new diagnoses had fallen between 2007-2014 due to the United States Preventative Services Task Force recommendations, the incidence rate has gradually increased since 2014. The vast majority of prostate cancer is diagnosed via transrectal ultrasound guidance through one of two approaches: the prostate can be repeatedly sampled by passing a needle through the rectum (transrectal, TR) or by passing a needle through the perineum (transperineal, TP). Given that there are over one million prostate biopsies performed in the United States every year, maximizing detection of clinically significant prostate cancer while minimizing biopsy-related complications is paramount.
In the TR approach, an 18-gauge biopsy needle is attached to the ultrasound probe and best samples the parts of the prostate closest to the rectum (peripheral zone and base). The TR approach traditionally under-samples the apex of the prostate and the anterior prostate. While magnetic resonance imaging (MRI) fusion targeting may direct the urologist to sample these areas, they may be missed on the routine standard template. This has been reproduced in the literature, as past studies have shown that TR prostate biopsies can miss up to 1/3 of clinically significant cancers and may under-stage up to ¼ of men based on radical prostatectomy final pathology. The TR approach is not without risk of complication either; in a 2011 SEER analysis, the authors reported a 30-day hospitalization rate of 6.9% and a 30-day mortality rate of 0.31% after TR prostate biopsy. Infection rates after TR biopsy with or without hospitalization have ranged between 0.38%-4.2%. Many of these infections are thought to be due to multidrug-resistant bacteria which have evaded past strategies aimed at infection mitigation such as rectal swabbing.
While not a new technique, TP prostate biopsy offers an alternative approach that may address rising concerns regarding accurate sampling and infectious complications posed by the TR approach. The first ultrasound-guided TP approach was described by Holm and colleagues in 1982. The biopsy needle can be introduced through the perineum with the assistance of a variety of needle guides including a mechanical stepper and grid system, 1-2 16-gauge angiocatheters introduced on either side of the urethra, Precision Pont tracking system (Perineologic ® Cumberland, MD), or without any needle guide. While procedural proficiency without MRI fusion may be achieved as early as 15 cases in, the learning curve for tangibly improving cancer detection via the TP approach with MRI fusion occurs after 125 cases. A systematic review looking at MRI fusion biopsies via the TP and TR approaches conducted by Rai and colleagues found that on a per-patient basis, TP had significantly better clinically significant cancer detection rates. This was driven primarily by better detection in anterior lesions as the pooled per-lesion detection rates for unspecified locations was not significantly different. A multicenter retrospective study conducted by Zattoni and associates showed that the overall cancer detection and clinically significant cancer detection rate was better with the TP approach over the TR approach. They also showed TP biopsies had a significantly higher likelihood of detecting clinically significant cancer in the apex, anterior zone, and transition zone.
While improved detection is advantageous, the major driver in the shift to the TP approach has been the decreased infection risk. A meta-analysis conducted by Castellani and colleagues found that patients who underwent TP biopsy with appropriate antibiotic prophylaxis (AP) had a pooled fever rate of 0.69%, pooled genitourinary infection rate of 0.11%, and a pooled sepsis rate of 0.13%. The rates of infectious complications are sufficiently low that there is now randomized evidence that in appropriately selected patients, TP biopsy with no AP is non-inferior to administering AP. The infections in TP biopsies are thought to be due to obstructive urosepsis, rather than inoculation of rectal flora into the urinary tract that can occur as a result of TR biopsies. Urinary retention after TP biopsies is more common than in TR biopsies, with rates ranging from 0.5-7.9%. Remaining questions to be definitively answered are centered around peri-procedural pain as a patient-reported outcome in the TP vs. TR setting as well as total cost of the procedures. To this end, there are multiple clinical trials underway investigating TR versus TP in a randomized, prospective fashion looking at infection adverse events, patient-reported pain and discomfort, detection of clinically significant prostate cancer, cost of the procedures, as well as patient-reported sexual dysfunction. While these trials will answer some of the remaining questions, there is little doubt the TP approach will continue to gain traction throughout the urologic community and grow in a variety of practice settings.
