SIU 2017: The Utility of Subsequent Prostate Biopsies for the Active Surveillance of Prostate Cancer when Genomics and MRI Are Negative
As an introduction, Dr. Cooperberg noted that AS has finally been recognized as the standard of care for low-risk PCa, as opposed to an option. However, those same guidelines do NOT mention high-risk groups, such as African-Americans, younger men, and high volume disease. While AS currenty entails an initial biopsy and a confirmatory biopsy at 6-12 months, following by surveillance regimens that vary significantly, most surveillance protocols still call for repeat biopsies during follow-up. However, along this management course, there are numerous new genomic tests that can be utilized to alter risk level as well as mpMRI. How do these tests affect decision making and can they replace biopsy?
Dr. Egawa began by highlighting the role of AS in Japan. Specifically, it is still significantly underutilized in Japan (< 5%). Part of the concern is that Korean men, and Asian men in general present with more aggressive disease. As such, they are utilizing much more stringent follow-up. As such, they have not allowed replacement of the biopsy yet. MRI is used frequently however.
Dr. Klotz and Dr. Kim then used ProtecT to point that even the substandard Active Monitoring had excellent prostate cancer survival. AS therefore is an excellent management that is safe in a selected population – the problem is accurately identifying that population. Gleason grade, for better of worse, is still pretty good at selecting patients for AS. However, the heterogeneity between lesions and even within lesions in the same prostate are what lead to the concern for undiagnosed higher risk disease. This is where molecular assessment may be helpful – by assessing the tissue or genome as a whole, rather than as specific cores, it may reveal some genomic predisposition to worse outcomes. However, a study by Wei et al (2016) demonstrated significant genomic heterogeneity even with a single tumor. A caveat though is a situation with an abnormal genomic score but normal biopsy – what do you do then? mpMRI is not without its flaws as well. While it has a NPV >90% in some series, others have not been able to replicate it – ranges from 60-90% elsewhere. It also does not detect all tumors. Importantly, Dr. Klotz presented data regarding the ASIST trial – specifically, about 8% had upgrading on the systematic biopsy but not the target biopsy. Therefore, MRI alone, even with targeted biopsy, does not capture all significant prostate cancer. He concludes by saying it is too soon to give up on systematic biopsies; but nomograms incorporating MRI may be warranted now.
Dr. Mulders’ notes that the experience with MRI in his center has been very good, with NPV 95%. As such, in their institution, they have foregone biopsy in MRI is negative. However, these results are not necessarily generalizable.
Overall, there was no consensus. The results of MRI are too inconsistent across even established centers to forego biopsy at this time.
Panelists: Shin Egawa, Wun-Jae Kim, Laurence Klotz, Peter Mulders
Written by: Thenappan Chandrasekar, MD, Clinical Fellow, University of Toronto, Twitter: @tchandra_uromd at the 37th Congress of Société Internationale d’Urologie - October 19-22, 2017- Lisbon, Portugal