Furthermore, the NPV of an MRI depends on the definition of a negative MRI. Classifying PIRADS 3 as a “positive” or “negative” MRI matters. Dr. Arsov argued that apart from MRI, there are other clinical predictors of high grade disease that are important to consider, such as PHI, PCA3, and other genomic markers and risk-calculators. PSA density (PSAD), in particular, has been shown to have nearly identical ROC test characteristics as MRI for detecting prostate cancer; hence, men with a high PSAD but without suspicious MRI findings should still probably receive a biopsy.
We also should not forgo the use of systematic biopsy, as stated earlier. Although standard TRUS biopsies tend to miss anterior lesions, evidence suggests that targeted biopsies are prone to miss lesions in the dorsolateral prostate – so these biopsy approaches are complementary, not stand-alone. Indeed, during follow-up, systematic biopsy appears to reclassify patients at a higher rate than fusion biopsies. Another important point is that fusion biopsy does not do well at diagnosing multifocal prostate cancer. Is the MRI index lesion really of prognostic relevance? Evidence suggests that tumor heterogeneity within the prostate predicts biological outcome, so maybe we shouldn’t just focus on MRI index lesions.
In summary, Dr. Arsov argues that complete reliance on MRI targeting may be premature. Given the continued variability in experience using MRI targeting and interpretation, both by Radiologists and Urologists, perhaps we shouldn’t be rushing to make MRI-based biopsies the only standard of care.
Speaker: C. Arsov, Düsseldorf (DE)
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