Making an art into a science: a mathematical "Likert tool" can change PI-RADS (v2) scores into Likert scores when reporting multiparametric MRI for prostate cancer.

Abstract

When reporting multiparametric magnetic resonance imaging (mpMRI) for prostate cancer, UK national guidelines recommend allocating both Likert and PI-RAD scores. Likert scores have been shown to better predict clinically significant cancer (csPCa) but are subjective and lack standardization. To compare differences in outcomes between the scoring systems and create a mathematical tool that can help to objectively allocate Likert scores. A total of 791 patients referred with query prostate cancer between 2017 and 2019 were prospectively allocated PI-RADS and Likert scores by a single experienced reporter. Histology results were used to compare the predictive accuracy of both scoring systems. A "Likert tool" was created based on a logistic regression of features found to be predictors of csPCa in a cohort of 2018-2019 patients (n = 411). Its performance was evaluated. Assuming a policy whereby patients with a PI-RADS/Likert score of ≥3 are biopsied, Likert scoring (sensitivity 0.92, specificity 0.77) would have resulted in 107 fewer biopsies and 20.3% higher cancer yields than the PI-RADS score (sensitivity 0.99, specificity 0.43). Thirteen patients would have avoided over-diagnosis of clinically insignificant prostate cancer (iPCa). Similar outcomes (111 fewer biopsies, 22.3% increase in cancer yield, iPCa diagnosis avoided in 16 patients) could be seen when the "Likert tool" was applied to the same patient cohort (sensitivity 0.93, specificity 0.79) and to a separate cohort (n = 380). PI-RADS and Likert scores are different. A "Likert tool" could reduce inter-reporter variability, decrease the number of patients unnecessarily biopsied, increase csPCa yield, and decrease over-diagnosis of iPCa.