All society guidelines currently recommend that confirmatory biopsies be taken within 12 months for men placed on AS. However, how frequently should we continue to take surveillance biopsies after that? Should it be on a specified time schedule, or should there be specific triggers to biopsy? The question is particularly relevant given data from the PRIAS prospective AS trial suggesting that while men demonstrate good compliance with obtaining serial PSAs over time, the use of serial surveillance biopsies is only 30%. In fact, retrospective work by Loeb et al. on SEER data suggests that for men with prostate cancer being watched, <10% receive a surveillance biopsy after 4 years.
So, is this steep decline in repeat AS biopsies important? Dr. Rannikko argues that it probably is not. Data from the “pre PSA”-era suggests that T1a prostate cancers are not usually dangerous – even without repeat biopsies, the long term cancer-specific survival of these patients is excellent. The recently published ProtecT trial had a monitoring arm that was based on serial PSA measurements, not on protocolized repeat biopsies. The 10-year survival of these men did not differ from the treatment arms, although progression was higher in the monitoring group (likely due to the inclusion of men with intermediate-risk disease that would nowadays not be considered for surveillance).
Data from the PRECISION trial were released at the EAU today, showing that MRI-based diagnostic biopsies are superior to standard protocol biopsies for increasing the detection of clinically significant cancers and limiting the detection of clinically insignificant cancers. So, we have good evidence that MRI is clearly a useful tool.
MRI reduces misclassification and has a high negative predictive value, but suffers from being highly user-dependent. For monitoring on AS, only a few papers have been published and the exact benefit of MRI in this space is unclear. For example, when considering cancer reclassification on AS, 24-55% of upgrading is by standard biopsy vs. only 15% upgrading by fusion biopsy alone.
Dr. Rannikko concluded that after placement on AS and after obtaining a confirmatory biopsy, further surveillance biopsies may not be as important as previously thought. And although MRI is an important tool in the detection and diagnosis of prostate cancer, its utility in monitoring men while on AS is still unclear.
We are still at the early stages of incorporating MRI-based imaging and biopsy technology into our management paradigms for men with prostate cancer. There are clearly areas that need further clarification from prospective data, but the likelihood is that MRIs will play a key role in the management of men on AS in the future.
Speaker: Antti Rannikko, Helsinki (FI)
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