So, can MRI consistently detect men who need treatment? Several studies, such as from Memorial Sloan Kettering and the PRIAS prospective active surveillance study show a clear trend that men with higher score MRI lesions have higher grade disease on biopsy, especially with PIRADS scores >3. Although the test characteristics vary somewhat between studies, it is now well-established that PIRADS 4-5 lesions have a high likelihood of representing clinically significant cancer and should be biopsied.
The role of MRI after patients are already on AS protocol is less clear. Data from the PRIAS study shows that men are far less likely to consent to protocol biopsies as time passes on AS; and it is evident that Urologists are not convinced of this necessity either. Hence, there is a real demand for decreasing the number of biopsies performed, and the use of MRI may help balance risks of excessive biopsies with risks of under-detection. For that reason, Dr. Moore suggests that only PIRADS lesions >=3 undergo biopsy, especially while on AS protocol.
It is unclear if MRI alone is the most appropriate way to follow men on AS. Clearly, baseline MRI findings are important in predicting future positive biopsies, but negative predictive values appear to maximize when using a combination of measures such as PSA density and MRI score. Hence, a multimodal approach is recommended when following men on AS when deciding on the performance of further biopsies.
In summary, Dr. Moore argues that MRI is able to detect cancers that need immediate treatment. Combination approaches (MRI score + PSA density) are able to deliver high negative predictive rates for men on AS who don’t need treatment or further biopsies. This is important because men clearly don’t like serial protocol biopsies while on AS, so developing ways to minimize the use of biopsy is a worthwhile task. Therefore, our growing reliance on MRI-targeted lesions is justified for men being chosen for AS or who are on AS already.
Speaker: C. Moore, London (GB)
Written by: Shreyas Joshi, MD, Fox Chase Cancer Center, Philadelphia, PA, Twitter: @ssjoshimd, at the 2018 European Association of Urology Meeting EAU18, 16-20 March, 2018 Copenhagen, Denmark