Target practice.

Top Line: What’s your threshold for recommending a prostate biopsy?
The Study: This one’s not about using MRI to enhance your biopsy technique. According to a recent JAMA Onc pub, MRI can now be used to enhance your predictions of “clinically significant” prostate cancer (with a Gleason score of at least 3+4). At the National Cancer Institute (NCI), elevated PSA and/or a suspicious digital rectal exam prompts a prostate MRI. If MRI findings are PI-RADS score 3 (equivocal for cancer) to 5 (highly likely to be cancer), MRI-transrectal ultrasound (TRUS) guided biopsies of the largest lesion with the highest PI-RADS score is typically obtained prior to the standard 12-core approach. Side note: How is the MRI used? It’s segmented and then co-registered in real-time with the TRUS. 400 of these NCI cases were used to create an MRI prediction model which was then validated on 251 patients at two other institutions (also with expert uro-radiologists). When compared to a widely-accepted clinical prediction model, the MRI model resulted in far fewer false positives and slightly more false negatives. Using a MRI model risk threshold of 20% in the validation cohort, 96 of 251 patients (38.2%) would have been spared a biopsy while 11 of 96 patients (11.5%) with clinically significant disease would have been missed. The downside? Generalizability, as in to radiologists with varying experience and to patients of varying means.
Bottom Line: Using a prostate MRI to predict cancer likelihood can reduce unnecessary prostate biopsies, at least if you’re at a high-volume, high-resource center like the NCI.


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