Assessment of prostate cancer aggressiveness using apparent diffusion coefficient values: impact of patient race and age

Purpose: To assess the impact of patient race and age on the performance of apparent diffusion coefficient (ADC) values for assessment of prostate cancer aggressiveness. Materials and methods: 457 prostate cancer patients who underwent 3T phased-array coil prostate MRI including diffusion-weighted imaging (DWI; maximal b-value 1000 s/mm²) before prostatectomy were included. Mean ADC of a single dominant lesion was measured in each patient, using histopathologic findings from the prostatectomy specimen as reference. In subsets defined by race and age, ADC values were compared between Gleason score (GS) ≤ 3 + 4 and GS ≥ 4 + 3 tumors. Results: 81% of patients were Caucasian, 12% African-American, 7% Asian-American. 13% were <55 years, 42% 55–64 years, 41% 65–74 years, and 4% ≥75 years. 63% were GS ≤ 3 + 4, 37% GS ≥ 4 + 3. ADC was significantly lower in GS ≥ 4 + 3 tumors than in GS ≤ 3 + 4 tumors in the entire cohort, as well as in Caucasian, African-American, and all four age groups (P ≤ 0.015). AUC for differentiation of GS ≤ 3 + 4 and GS ≥ 4 + 3 as well as optimal ADC threshold was Caucasian: 0.73/≤848; African-American: 0.76/≤780; Asian-American: 0.66/≤839: <55 years, 0.73/≤830; 55–64 years, 0.71/≤800; 65–74 years, 0.74/≤872; ≥75 years, 0.79/≤880. A race-optimized ADC threshold resulted in higher specificity in African-American than Caucasian men (84.9% vs. 67.1%, P = 0.045); age-optimized ADC threshold resulted in higher sensitivity in patients aged ≥75 years than <55 years or 55–64 years (100.0% vs. 53.6%–73.3%; P < 0.001). Conclusion: Patients’ race and age may impact the diagnostic performance and optimal threshold when applying ADC values for evaluation of prostate cancer aggressiveness.