Impact of mandated prospectively reported apparent diffusion coefficient values on the rates of positivity for clinically significant prostate cancer by PI-RADS score

Background Prior research has shown that retrospectively measured apparent diffusion coefficient (ADC) of prostate magnetic resonance imaging (MRI) lesions is associated with clinically significant prostate cancer (csPCa) on targeted biopsy suggesting that ADC should be measured and reported prospectively. Purpose To assess the impact of mandatory prospective measurement of ADC on the rates of positivity across PI-RADS scores for csPCa. Material and Methods Consecutive patients who underwent ultrasound (US)-MRI fusion prostate biopsy from August 2018 to July 2019 and who had prospectively reported ADC were compared to control patients who did not. Rates of positivity by PI-RADS category were computed and compared using Chi-square. Multivariable regression was performed. Results In total, 126 patients (median age 65 years) with 165 prostate lesions (19, 51, 70, and 25 PI-RADS 2, 3, 4, and 5, respectively) and prospectively reported ADC values were compared to 113 control patients (median age 66 years) with 157 prostate lesions (17, 42, 64, and 34 PI-RADS 2, 3, 4, and 5, respectively). Rates of positivity across PI-RADS scores were similar between the two cohorts; 11%, 25%, 55%, and 76% and 0%, 21%, 56%, and 62% for PI-RADS 2, 3, 4, and 5 in the test and control cohorts, respectively (Chi-square P = 0.78). Multivariate logistic regression showed no significant association between the presence of prospectively measured ADC and csPCa (odds ratio 1.1, 95% confidence interval 0.7–1.7, P = 0.82). Conclusion Prospective ADC measurement may not impact PI-RADS category assignments or positivity rates for csPCa under current guidelines. Future versions of PI-RADS may need to incorporate ADC into scoring rules to realize their potential.