BIPARAMETRIC QUANTITATIVE MRI FOR PROSTATE CANCER DETECTION

INTRODUCTION AND OBJECTIVE: Prostate Cancer (PC) detection using the quantitative MRI parameter, apparent diffusion coefficient (ADC), has been shown to improve accuracy over the Prostate Imaging Reporting & Data System (PI-RADS), however insufficient evidence exists for the use of any quantitative MRI parameter in biopsy selection. We aimed to prospectively investigate the fractional order calculus (FROC) estimation of diffusion to better predict PC compared to ADC and PI-RADS. METHODS: A prospective pilot study (NCT04175730) was conducted in biopsy naïve men with PSA 4 and 20 ng/mL without prior diagnosis of PC. All men received 3T MRI with T2 weighted, mapping and diffusion weighted imaging (DWI) using ten b-values (50 e 4000 s/mm). Men with PI-RADS <3 lesions seen on MRI underwent 12 systematic biopsies, men with central zone PI-RADS 3 lesions underwent fusion targeted biopsy and six systematic biopsies, and men with peripheral zone PI-RADS 3 lesions underwent fusion targeted biopsies. Using the DWI series, the corresponding PIRADS 3 lesions (or peripheral zone area in negative MRIs) were fit a mono-exponential signal decay diffusion model to calculate ADC (mm/s) and the FROC model with diffusion coefficient DF (mm /s). The primary endpoint was detection of Gleason grade group 2 (GG 2) PC. Univariate Kruskal-Wallis and chi-squared tests as well as 95% confidence intervals were used when applicable. GG 2 PC discrimination was calculated using receiver operating characteristic regression and the area under the curve (AUC) was reported. RESULTS: In total, 48 men underwent MRI and biopsy. The mean age was 61.5 years (56-68), 29% were White, 52% were African American, mean PSA was 6.0 ng/mL (4.9-8.0), and mean PSA density was 0.14 ng/mL. In total 61 PI-RADS 3 lesions were found with 38% (23) in the central zone and 62% (38) in the peripheral zone. GG 2 PC was found in 7% (1/14) of PI-RADS 3 lesions, 28% (10/36) of PI-RADS 4 lesions, and 36% (4/11) of PI-RADS 5 lesions. Mean ADC for PC was 0.78 (0.68-0.98) compared to 1.02 (0.86-1.15) in benign tissue (p[0.009). Mean DF was 1.2 (1.1-1.4) for PC compared to 1.4 (1.41.5) in benign tissue (p[0.002). The AUC for detection of GG 2 PC was 0.63 (0.5-0.76) for PI-RADS, 0.82 (0.68-0.96) for ADC, and 0.87 (0.77-0.97) for the FROC model. CONCLUSIONS: In this small prospective pilot study we show modeling of MRI signal diffusion using the FROC model may provide improvement in PC detection over ADC and PI-RADS. Further study including larger populations may confirm these findings.