The improvement of prostate MRI is among the most transformative developments in PCa detection over the past decade. Use of MRI prior to prostate biopsy is rapidly increasing; however, there remain barriers to widespread adoption, with many urologists reporting persistent difficulty obtaining insurance coverage.
Increasing evidence of pre-biopsy mpMRI indication in Prostate Cancer diagnosis
These are very exciting times in prostate imaging, with a rapidly expanding body of literature on prostate magnetic resonance imaging (MRI).
Recent studies using different data sources provide corroborative evidence that the use of MRI prior to prostate biopsy has been steadily increasing over time. However, the data show that MRI was still used in the minority of cases as of 2016, particularly in the biopsy-naive population.
In April 2016, the American Urological Association and Society of Abdominal Radiology issued a Joint Consensus Statement describing the ongoing need for strategies to select patients for repeat biopsy. They state that when high-quality prostate MRI is available, it should be strongly considered in any patient with a prior negative biopsy who has persistent clinical suspicion for prostate cancer (PCa) and who is undergoing a repeat biopsy.
There is also growing evidence supporting a role for MRI prior to initial prostate biopsy. PROMIS (PROstate MRI Imaging Study), a prospective, multicenter study, examined the diagnostic accuracy of multiparametric MRI (mpMRI) and transurethral ultrasound (TRUS) biopsy compared with the reference standard of template mapping biopsy in men with a PSA level below 15 ng/mL and no prior biopsy. They found that mpMRI was more sensitive (93% vs 48%) and less specific (41% vs 96%) than TRUS biopsy for the detection of clinically significant cancer. The authors concluded that using MRI prior to prostate biopsy could reduce overdiagnosis of insignificant cancer and improve detection of clinically significant cancer.In May 2018, the multicenter randomized PRECISION (Prostate Evaluation for Clinically Important Disease: Sampling Using Image Guidance or Not?) trial was published in the New England Journal of Medicine. In this trial, 500 men with elevated PSA and no prior biopsy were randomized to undergo standard TRUS-guided biopsy versus MRI with or without targeted biopsy. In the MRI arm, 28% of participants had a negative MRI (scores less than 3) and did not undergo biopsy. The primary outcome was the proportion of men diagnosed with clinically significant cancer, defined as any Gleason score of 3+4 or higher. Overall, clinically significant cancer was found in 38% of the MRI-targeted biopsy group vs 26% of the standard biopsy group.
Despite this level 1 evidence, there seems to be a disconnect with insurance coverage for MRI prior to initial prostate biopsy.
Aside from issues with insurance coverage of MRI, other challenges remain in its widespread implementation. For example, studies have shown significant variability in the quality of mpMRI cross centers and in interpretation between radiologists, highlighting the importance of quality control. Another challenge is what to do about biopsy in cases where MRI is negative. In PRECISION, a quarter of men had a negative MRI and biopsy was not performed. This is controversial, however, since some significant cancers may be missed resulting in potential delayed diagnoses. A recent consensus conference in the UK concluded that pre-biopsy mpMRI scoring should not be the only factor guiding biopsy decisions. They suggested that other factors such as age, family history, use of 5-alpha reductase inhibitors, total PSA, PSA kinetics, PSA density, urine dipstick results, prior biopsy results, and patient preference can also be factored into the decision.
Moving forward, an important factor influencing implementation of MRI-based protocols is how to optimally integrate imaging with other markers into the detection and management paradigm. The combination of MRI plus a marker test (such as PSA density or the Prostate Health Index) has higher negative predictive value and therefore greater confidence to exclude a biopsy than MRI alone.
In conclusion, the improvement of prostate MRI is among the most transformative developments in PCa detection over the past decade. Use of MRI prior to prostate biopsy is rapidly increasing; however, there remain barriers to widespread adoption, with many urologists reporting persistent difficulty obtaining insurance coverage.
Veeru Kasivisvanathan, M.R.C.S., Antti S. Rannikko, Ph.D., Marcelo Borghi, M.D., Valeria Panebianco, M.D., Lance A. Mynderse, M.D., Markku H. Vaarala, Ph.D., Alberto Briganti, Ph.D., Lars Budäus, M.D., Giles Hellawell, F.R.C.S.(Urol.), Richard G. Hindley, F.R.C.S.(Urol.), Monique J. Roobol, Ph.D., Scott Eggener, M.D., et al., for the PRECISION Study Group Collaborators. MRI-Targeted or Standard Biopsy for Prostate-Cancer Diagnosis. N Engl J Med 2018; 378:1767-1777 DOI: 10.1056/NEJMoa1801993