Patient-level detection of grade group ≥2 prostate cancer using quantitative diffusion MRI

Abstract

Purpose: Multiparametric MRI (mpMRI) improves detection of clinically significant prostate cancer (csPCa), but the qualitative PI-RADS system and quantitative apparent diffusion coefficient (ADC) yield inconsistent results. An advanced Restrictrion Spectrum Imaging (RSI) model may yield a better quantitative marker for csPCa, the RSI restriction score (RSIrs). We evaluated RSIrs for patient-level detection of csPCa. Materials and Methods: Retrospective analysis of men who underwent mpMRI with RSI and prostate biopsy for suspected prostate cancer from 2017-2019. Maximum RSIrs within the prostate was assessed by area under the receiver operating characteristic curve (AUC) for discriminating csPCa (grade group ≥2) from benign or grade group 1 biopsies. Performance of RSIrs was compared to minimum ADC and PI-RADS v2-2.1via bootstrap confidence intervals and bootstrap difference (two-tailed α=0.05). We also tested whether the combination of PI-RADS and RSIrs (PI-RADS+RSIrs) was superior to PI-RADS, alone. Results: 151 patients met criteria for inclusion. AUC values for ADC, RSIrs, and PI-RADS were 0.50 [95% confidence interval: 0.41, 0.60], 0.76 [0.68, 0.84], and 0.78 [0.71, 0.85], respectively. RSIrs (p=0.0002) and PI-RADS (p<0.0001) were superior to ADC for patient-level detection of csPCa. The performance of RSIrs was comparable to that of PI-RADS (p=0.6). AUC for PI-RADS+RSIrs was 0.84 [0.77, 0.90], superior to PI-RADS or RSIrs, alone (p=0.008, p=0.009). Conclusions: RSIrs was superior to conventional ADC and comparable to (routine, clinical) PI-RADS for patient-level detection of csPCa. The combination of PI-RADS and RSIrs was superior to either alone. RSIrs is a promising quantitative marker worthy of prospective study in the setting of csPCa detection.

Background prostate tissue is quantitatively abnormal on MRI in patients with clinically significant prostate cancer

“…T 2 -weighted signal in BP contributes meaningful information and may have diagnostic or prognostic clinical value. We have previously shown that a quantitative DWI biomarker called RSI C 1 is useful for voxel-level and patient-level detection of csPCa (14,15). Median T 2 in the prostate was not correlated with maximum RSI C 1 , and patient-level csPCa detection improved after normalizing maximum RSI C 1 by median T 2 .…”

“…RSI C 1 signal was computed from the DWI data of each patient by fitting with a previously described 4-compartment RSI model (13,14). Prior studies have employed the maximum C 1 value within the prostate as a diffusion-based indicator of prostate cancer (14,15), so the maximum C 1 value within the prostate was recorded for each patient in the present study. The Pearson correlation was then computed between the median T 2 -weighted signal and maximum C 1 value in the prostate.…”

“…Patients were included in analyses if they had no prior treatment for prostate cancer; in the larger cohort 2, patients were additionally excluded if they did not have a biopsy within 6 months of the MRI. Both cohorts have been studied previously for characterization of signal in lesions (13)(14)(15). BP signal has not been reported previously.…”

ReIGNITE RT Boost: An international study testing the accuracy and feasibility of using restriction spectrum imaging (RSI) MRI to guide intraprostatic tumor target volume for radiotherapy boost

“…We previously developed a quantitative diffusion MRI biomarker for PCa, called the Restriction Spectrum Imaging restriction score (RSIrs), that significantly improves diagnostic utility over conventional MRI. 6,7 RSI is a sophisticated but practical approach that models tissue microcompartments to highlight the restricted intracellular diffusion characteristic of higher-grade PCa. 8 We hypothesized that using RSIrs maps would improve radiation oncologists' accuracy for PCa tumor delineation.…”