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

BackgroundT2-weighted MRI is standard for detecting clinically significant prostate cancer (csPCa) by identifying visible lesions that stand out from the background prostate. PurposeTo determine whether patients with csPCa have abnormal T2-weighted signal in non-lesion, background prostate tissue (BP). MethodsThis retrospective study included two patient cohorts who underwent 3T MRI examination for suspected csPCa. Median (urine-normalized) T2-weighted signal was computed for BP and compared between patients with and without csPCa. csPCa discrimination performance of T2-weighted BP signal was evaluated using area under receiver operating characteristic curves (AUC). T2 and S0 (a proxy for proton density) were computed and compared between patients with and without csPCa. T2 was also recomputed using larger buffers around csPCa lesions. csPCa discrimination performance was compared between two predictors: Restriction Spectrum Imaging (RSI) C1 and RSI C1 normalized by global prostate median T2-weighted signal. ResultsCohort 1: 46 patients (age: 64{+/-}10 years). Cohort 2: 151 patients (65{+/-}8 years). Urine-normalized T2-weighted signal was systematically lower in BP of subjects with csPCa (p[≤]0.034) and indicated the presence of cancer (cohort 1: AUC=0.80; cohort 2: AUC=0.68). BP T2 was significantly lower in csPCa patients (p[≤]0.011), while S0 was not (p[≥]0.30). BP T2 measurements were stable to within 5% with buffers from 0 to 30 mm around visible lesions. csPCa discrimination improved with incorporation of BP T2-weighted signal (cohort 1: AUC=0.72 for RSI C1 alone, versus 0.81 with BP T2-weighted signal; cohort 2: AUC=0.63 versus 0.76). ConclusionLower T2-weighted signal in BP suggests the presence of csPCa.