AUA 2017: Combining 4KScore and Magnetic Resonance Imaging (MRI) for Prostate Biopsy Decision Making

Boston, MA (UroToday.com) At the prostate cancer (PC) diagnosis and screening podium session during the 2017 American Urological Association’s Annual Meeting, Dr. Karim Marzouk and his colleagues presented their work from the Memorial Sloan Kettering Cancer Center assessing the utility of multiparametric MRI (mpMRI) as a follow-up test to the 4Kscore. As the recently published PROMIS MRI trial demonstrated, 11% of men with a normal MRI will have high-grade disease.1 Since we have many biomarkers that include imaging modalities available to clinicians in the prebiopsy setting, studies delineating appropriate patient-specific sequences of tests are important.

In this study, the 4Kscore results from the United States prospective validation study were combined with mpMRI data available from the PROMIS study. The co-authors used likelihood ratios for MRI that  detected high-grade disease from PROMIS (positive and negative likelihood ratio of 1.58 and 0.17, respectively) and applied these ratios to probabilities of 4Kscores. Four unique populations were identified based on a threshold for biopsy of 7.5% risk of high-grade disease: (i) men with a very low 4Kscore for whom risk would not be less than 7.5%, even with positive MRI, (ii) men with 4Kscores of less than 7.5% whose risk would be 7.5% or more if the MRI was positive, (iii) men with 4Kscores of 7.5% or higher whose risk would be less than 7.5% if the MRI was negative, and (iv) men with high 4Kscores whose risk would remain 7.5% or greater, even if MRI was negative. In the 4Kscore validation study, 1012 men underwent prostate biopsy, with 23% being diagnosed with Gleason 7 or higher disease. The range of 4Kscores that could be influenced by the results of MRI included 26% of the population with a risk of less than 5% (group 1), 10% with a risk of 5.0%-7.4% (group 2), 45% with a risk of 7.5%-32% (group 3), and 21% with a risk of more than 32% (group 4). Importantly, the net benefit of using 4Kscores alone was 17.7%, mpMRI of 17.6%, and combined strategies of 18.2%.

In summary, this is an sophisticated study combining imaging and biomarkers to further delineate who should or should not undergo a biopsy. Using mpMRI in the setting of low-to-intermediate 4Kscores results in a biopsy strategy with a higher net benefit compared to using either modality alone.
Presented By: Karim Marzouk, MD, Memorial Sloan Kettering Cancer Center, New York, NY, USA

Co-Authors: Behfar Ehdaie, MD; Stephen Zappala, MD; Andrew Vickers, PhD

Written By: Zachary Klaassen, MD, Urologic Oncology Fellow, University of Toronto, Princess Margaret Cancer Centre, Toronto, Ontario, Canada
Twitter: @zklaassen_md

at the 2017 AUA Annual Meeting - May 12 - 16, 2017 – Boston, Massachusetts, USA

Reference:
1. Ahmed HU, El-Shater Bosaily A, Brown LC, et al. Diagnostic accuracy of multi-parametric MRI and TRUS biopsy in prostate cancer (PROMIS): a paired validating confirmatory study. Lancet. 2017;389:815-822.
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