We generated a study cohort of consecutive men who underwent prostate mpMRI from our prospective institutional registry. Measures of test performance (e.g. sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV)) were compared between the nine radiologists, who interpreted the studies as part of the clinical workflow of the abdominal imaging section at our institution. While most studies compare mpMRI to either radical prostatectomy or standard TRUS-guided biopsy histopathology, we utilized MRI-targeted biopsy core pathology as the reference standard.
Sensitivity, specificity, PPV and NPV were 83.6%, 50.5%, 41.0% and 88.2%, respectively. Although we found variation in test performance among individual radiologists, no significant differences were observed. Interestingly, the additional prostate mpMRI experience was not beneficial in improving accuracy. We found that a number of non-modifiable patient variables, including prostate lesion location, prior biopsy history, PSA, and age, were predictive of prostate mpMRI test performance (Table 1).
Table 1. Multivariate logistic regression analysis of clinical factors predictive of measures of test performance.
PSA = prostate-specific antigen; MRI = magnetic resonance imaging; PPV = positive predictive value; NPV = negative predictive value; CI = confidence interval.
As our use and understanding of prostate mpMRI continue to grow, clinicians must remain aware of variability in the interpretation of this imaging modality, as well as the clinical factors that may affect its performance. The implementation of the PI-RADS scoring system has led to a significant reduction in such variability,7 which we expect will further improve with subsequent versions. Finally, while prostate mpMRI has emerged as the new de facto imaging test for the evaluation of localized prostate cancer, further study of newer technology is critical. Promising examples include contrast-enhanced ultrasound and shear wave elastography (for patients unable to undergo MRI), PSMA-PET/CT (for staging high-risk disease or detecting disease in patients with biochemical recurrence), diffusion tensor imaging, and high-resolution MRI.
Written by: Nicholas A. Pickersgill, BS and Eric H. Kim, MD, Division of Urology, Washington University School of Medicine, St. Louis, Missouri, United States
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