For decades, prostate cancer (PCa) diagnosis has depended on transrectal ultrasonography (TRUS) biopsy. The evolutionary journey of prostate biopsy began in the 1920s with the introduction of the first finger-guided transperineal (TP) needle biopsy and the open perineal prostate biopsy. In 1937, Astraldi conducted the first finger-guided transrectal (TR) prostate biopsy. The 1960s saw further advancements with the successful imaging of the prostate using a TRUS probe. In 1981, Holm et al. described the first TRUS-guided TP prostate biopsy, and in 1989, Hodge et al. introduced the first sextant TRUS-guided TR prostate biopsy, marking the start of the modern era of systematic biopsy for PCa.^1,2 More recently, work here at the National Institutes of Health (NIH), along with other research centers across the globe, has established multiparametric MRI of the prostate as the best imaging test to detect cancer within the prostate. The first in-bore MRI-guided prostate biopsy was performed transperineally on a patient with no rectum by D’Amico et al in 2000.³ Since then, to improve workflow and patient comfort and reduce health costs, MRI-TRUS image fusion targeted prostate biopsy, first described at the NIH by Xu et al in 2007,⁴ has emerged as the new standard method to detect PCa.⁵

The transition from TR biopsy to TP biopsy with a TRUS probe has gained popularity over concerns of increased infection risk and the need for broad-spectrum antibiotics with TR biopsy. This has sparked a heated debate on the best needle route for a prostate biopsy.⁶ Yet, even with the TP biopsy technique, as the TRUS probe is moved to image the apex of the prostate, it can bring fecal matter from the rectum into the field of work. In addition, from a patient comfort standpoint, the use of a TRUS probe remains a suboptimal option, in some cases leading to early abortion of the procedure. This is particularly a problem during TP biopsies of larger prostates at the base of the gland, which require deeper insertion of the TRUS probe with increased patient discomfort. The recent changes in prostate biopsy were also accompanied by a transition from general to local anesthesia that can be performed in an office setting. However, local anesthesia has not proven effective in addressing the discomfort caused by the TRUS probe.

At the Urologic Oncology Branch of the National Cancer Institute/NIH, we developed a novel fully TP (FTP) MRI/ ultrasound (US) image fusion targeted prostate biopsy device and custom software that utilizes a TPUS probe directly onto the patient’s perineum to image the prostate instead of a traditional TRUS probe (Figure).^7,8 In a study presented at the 2024 AUA annual meeting in San Antonio, we assessed the feasibility and performance of this novel prostate biopsy system, comparing cancer detection rates (CDR) between FTP and TP biopsies.⁹

Between 2018 and 2023, we enrolled patients at the NIH on a prospective registry undergoing MRI/US fusion targeted prostate biopsies using both FTP and TP methods. TP biopsies were performed with a TRUS probe using the commercially available UroNav MRI/US fusion biopsy platform, while FTP biopsies were performed using a TPUS curved array probe. We developed a novel software platform to allow TPUS fusion in real time with prostate MRI utilizing electromagnetic tracking. We compared CDR between FTP and TP biopsy on a per-session and per-lesion basis using McNemar’s test. We assessed baseline and clinical characteristics, including grade group, percentage of biopsy core involvement, size of tumor on biopsy, prostate volume, and lesion size on MRI. We also performed a multivariable logistic regression to determine predictors of discordance in cancer detection between FTP and TP biopsy.

A total of 277 prostate lesions were biopsied from 144 patients using both FTP and TP methods for each lesion in the same biopsy session.

In the per-session analysis, we found no significant difference in CDR between FTP and TP methods for both overall PCa (60%; P = 1) and clinically significant PCa (grade group ≥2; 34% vs 41%; P =.1).

In the per-lesion analysis, we found no significant difference in CDR using FTP vs TP methods for overall PCa (55% vs 54%; P =.8) and clinically significant PCa (29% vs 33%; P =.12).

On multivariable regression, prostate volume, anatomical location, and high-risk Prostate Imaging Reporting and Data System scores, commonly known as PI-RADS scores, were found to be predictors of discordance in cancer detection between both methods.

A main limitation of our study is that our novel FTP biopsy device has not been commercialized and therefore has not undergone large-scale validation and remains in its initial phases of development from both a device and a software perspective. Additionally, this comparative study lacks a definitive ground-truth reference, such as whole mount pathology following radical prostatectomy. In our cohort, the proportion of patients who progressed to radical prostatectomy was insufficient to power an evaluation of sensitivity and specificity. Future trials with larger cohorts, including a greater number of patients who undergo radical prostatectomy, should provide a better assessment of this novel technique’s efficacy and reliability.

In summary, our novel FTP biopsy device has shown comparable CDR to the traditional TP biopsy in detecting PCa. This innovative technique eliminates the need for a US probe in the rectum, offering a less invasive, more sterile, and more comfortable patient experience. Further design development and technical refinement are ongoing to optimize this new device’s availability for commercialization. This will hopefully one day allow urologists to abandon the TR probe during a prostate biopsy once and for all.