From Pages to Practice
Published May 9, 2018
Mr. Jenkens’ ashen-face speaks volumes about his interpretation of his prostate-specific antigen (PSA) test results. He whispers, “It’s cancer isn’t it?” Mr. Jenkens is a 67-year-old man who presented to your clinic 1 week ago with a long-standing history of urinary frequency and urgency with a prostate that was normal to palpation. As part of your investigation, you obtained a serum prostate-specific antigen (PSA) level that was elevated at 8 ng/mL. You counsel Mr. Jenkens about the role of serum PSA as a screening tool for prostate cancer and inform him that in addition to cancer, an elevated PSA can be indicative of other benign pathology. To establish a definitive diagnosis, further investigation must be performed.
While transrectal ultrasonography-guided prostate biopsy has classically been the standard of care for the diagnosis of prostate cancer, limitations in its sensitivity have led to poor detection of clinically significant prostate cancers and frequent detection of clinically insignificant prostate cancer. The additional downstream stress and costs related to active surveillance or overtreatment of clinically insignificant prostate cancer has prompted researchers to investigate alternative diagnostic regimens for prostate cancer, including multiparametric magnetic resonance imaging (MRI) and MRI-targeted biopsy. In small, nonrandomized, single-center studies, an MRI-targeted biopsy approach has shown favorable rates of detection of clinically significant cancer and lower rates of detection of clinically insignificant cancer as compared to standard biopsy.
In this week’s issue of NEJM, Kasivisvanathan and colleagues reported the results of the PRECISION trial (Prostate Evaluation for Clinically Important Disease: Sampling Using Image Guidance or Not?), a multicenter, randomized, noninferiority trial of MRI-targeted biopsy versus standard biopsy in men with clinical suspicion of prostate cancer. In all, 500 men with elevated PSA level, abnormal digital rectal examination, or both were randomized to undergo standard biopsy (up to 12 blindly obtained cores) or targeted biopsy based on multiparametric MRI abnormalities.
The proportion of men with clinically significant prostate cancer (the primary outcome) was 38% in the MRI-targeted biopsy group versus 26% in the standard biopsy group (P=0.005). Significantly fewer men in the MRI-targeted biopsy group received a diagnosis of clinically insignificant cancers (Gleason grade <7) than in the standard biopsy group (adjusted difference -13; P<0.001). Participant-reported health-related quality of life at 30 days did not differ between the two groups. Finally, fewer men in the MRI-targeted biopsy group underwent further diagnostic tests than in the standard biopsy group (3% vs. 16%).
In an accompanying editorial, Michael J. Barry and Andrew B. Rosenkrantz are cautiously enthusiastic about the study findings and suggest that the intermediate results could be practice changing. However, larger and longer-term studies of prostate cancer-related morbidity and mortality are needed to fully evaluate the role of multiparametric MRI as a diagnostic tool in this disease. Furthermore, the cost and resource intensive processing that may accompany widespread implementation of multiparametric MRI in prostate cancer screening need to be considered.
In men with suspected prostate cancer, MRI, with or without targeted biopsy, can identify a large proportion of men who could benefit from treatment while reducing the overtreatment of men with clinically insignificant cancers. In counselling Mr. Jenkens, he should be made aware of the higher chance of identifying clinically significant cancer and the potential to avoid a biopsy or further investigations should he pursue multiparametric MRI and MRI-targeted biopsy.