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

Abstract

Background:T2-weighted MRI is well established for detection of clinically significant prostate cancer (csPCa), but prior studies have primarily focused onT2within MRI-visible lesions.Purpose:To determine whether patients with csPCa have systematically abnormalT2-weighted signal in non-lesion, background prostate tissue (BP).Materials and Methods:This retrospective study included two patient cohorts who underwent 3T MRI examination for suspected csPCa between August 2016 and February 2020. Median (urine-normalized)T2-weighted signal was computed for BP. BP signal was compared between patients with and without csPCa, using two-samplet-tests (α=0.05). csPCa discrimination performance ofT2-weighted BP signal was evaluated using area under receiver operating characteristic curves (AUC).T2andS0(a proxy for proton density) were computed and compared between patients with and without csPCa using two-samplet-tests (α=0.05).T2was also recomputed with larger buffers around csPCa lesions. Finally, csPCa discrimination performance was compared between two predictors: maximum Restriction Spectrum Imaging (RSI)C1and maximum RSIC1normalized by global prostate medianT2-weighted signal.Results:Cohort 1: 46 patients (mean age: 64 years ±10 [standard deviation]). Cohort 2: 151 patients (age: 65±8 years). Urine-normalizedT2-weighted signal was systematically lower in BP of subjects with csPCa compared to those without (p≤0.034). BPT2-weighted signal indicated the presence of cancer (cohort 1: AUC=0.80; cohort 2: AUC=0.68). BPT2was significantly lower in csPCa patients compared to those without (p≤0.011), whileS0was not (p≥0.30). BPT2measurements were stable to within 5% using a buffer of 0 to 30 mm around visible csPCa lesions. csPCa discrimination improved with incorporation of global prostate medianT2-weighted signal (cohort 1: AUC=0.72 for maximum RSIC1alone versus 0.81 when normalized by medianT2-weighted signal; cohort 2: AUC=0.63 versus 0.76).Conclusion:LowerT2-weighted signal in BP suggests the presence of csPCa.