An Update on Imaging of Primary Prostate Cancer

(UroToday.com) At the Society of Urologic Oncology (SUO) Annual Meeting, Dr. James Wysock gave an update on the imaging for primary prostate cancer. Dr. Wysock briefly touched on imaging strategies in both the screening and diagnosis of localized prostate cancer.

The poor sensitivity and specificity in the screening and diagnosis of men with prostate cancer is a well-known limitation of our current technologies. Prostate-specific antigen (PSA0 directed screening and transrectal ultrasound (TRUS) guided biopsies lead to both the under-sampling of clinically significant prostate cancer as well as the overdetection of indolent prostate cancer. As a result, there has been increasing interest in the use of MRI and MRI targeted biopsies to aid in this diagnostic gap. Dr. Wysock presents data from Kim et al. demonstrating the rapidly increased use of prostate MRI in recent years reflecting this growing reliance on MRI-guided biopsies (Figure 1).

Dr. Wysock presented data from two landmark studies assessing the utility of MRI guided biopsies for cancer detection: the PROMIS, Diagnostic accuracy of multi-parametric MRI and TRUS biopsy in prostate cancer (PROMIS), and PRECISION, MRI-Targeted vs Standard Biopsy in Prostate Cancer Diagnosis: (The PRECISION Trial).

In the PROMIS trial, men underwent both an MRI guided biopsy and TRUS guided biopsy, which was then compared against the standard of a transperineal mapping biopsy1. The authors noted MRI guided biopsies were more sensitive for the detection of clinically significant prostate cancer than TRUS-guided biopsies alone. In the PRECISION trial, men were randomized to standard TRUS guided biopsy or an MRI directed strategy, in which men underwent a targeted biopsy if the prostate MRI was concerning for prostate cancer2. More men randomized to MRI were found to have clinically significant prostate cancer compared with men undergoing TRUS guided biopsy (38% and 26%, respectively). Furthermore, men randomized to the MRI arm were less likely to have biopsies identifying clinically insignificant disease compared with men in the TRUS guided biopsy arm. Importantly, approximately 20% of men randomized to the MRI arm avoided a biopsy altogether due to reassuring MRI findings. These studies suggest MRI stratified biopsy strategies are superior at detecting clinically significant prostate cancer while minimizing the detection of clinically insignificant disease. 

Highlighting some limitations from MRI and MRI targeted biopsies, Dr. Wysock presented data from Sonn et al. which demonstrates significant inter-observer variability between radiologists reading prostate MRIs, assigning PIRADS scores, and the subsequent detection of clinically significant cancers3. Hopefully, with standardization and improving familiarity with MRI and MRI guided biopsies, variability will decrease between radiologists assigning PIRADS scores and corresponding cancer detection on targeted biopsies, thus further improving the utility of these technologies.

Dr. Wysock briefly discusses the role of MRI as a potential screening tool for prostate cancer, purposing MRI may function in the future similar to mammography for breast cancer or low-dose CT scan lung cancer, two cancer which screening programs rely heavily on imaging modalities. Additionally, 29Mhz high-resolution micro-ultrasound is an emerging technology that may play a role in the screening and detection of clinically significant prostate cancer in the future, although these data are still immature. 

Levering MRI and other enhanced imaging technologies show significant promise and improved accuracy compared to the status quo in almost all states of prostate cancer care including the screening, detection, staging, and monitoring of men with prostate cancer. This author anxiously awaits further studies integrating these technologies into prostate cancer screening, detection, and treatment paradigms.

Presented by: Dr. James Wysock, MD, MSc. Urologic Oncologist, NYU Langone Health, New York, New York, United States. 

Written by: Kevin Ginsburg, MD, and Adrien Bernstein, MD, Society of Urologic Oncology Fellow, Fox Chase Cancer Center, Fox Chase Cancer Center, Philadelphia, PA, at the 2020 Society of Urologic Oncology Annual Meeting – December 2-5, 2020 – Washington, DC

References
1. Ahmed, H. U., El-Shater Bosaily, A., Brown, L. C. et al. Diagnostic accuracy of multi-parametric MRI and TRUS biopsy in prostate cancer (PROMIS): a paired validating confirmatory study. Lancet, 389:815, 201
2. Kasivisvanathan, V., Rannikko, A. S., Borghi, M. et al. MRI-Targeted or Standard Biopsy for Prostate-Cancer Diagnosis. N Engl J Med, 378: 1767, 2018
3. Sonn, G. A., Fan, R. E., Ghanouni, P. et al. Prostate Magnetic Resonance Imaging Interpretation Varies Substantially Across Radiologists. Eur Urol Focus, 5: 592, 2019

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