Endorectal magnetic resonance imaging for predicting pathologic T3 disease in Gleason score 7 prostate cancer: Implications for prostate brachytherapy

Abstract

To determine the ability of endorectal magnetic resonance imaging (erMRI) and other pretreatment factors to predict the presence and extent of extraprostatic extension (EPE) in men with Gleason score (GS) 7 prostate cancer. We included patients with clinical stage T1c-T2c, GS=7 (3+4 or 4+3), and prostate-specific antigen (PSA) <10ng/mL who underwent pre-prostatectomy erMRI. We compared pathologic EPE findings with pretreatment factors. One hundred seventy-one men were eligible for inclusion. Pretreatment characteristics were: median age=60 years (42-76); median PSA 4.9ng/mL (0.4-9.9); GS 3+4=61%; T1c=51%; T2a=25%; T2b=21%; T2c=3%; ≥50% positive cores=46%; EPE-positive (EPE+) erMRI=28%. Thirty-three percent had pathologic EPE. Increasing T-stage (p<0.0001) and EPE+ erMRI (p<0.0001) were significant predictors of pathologic EPE, whereas GS (4+3 vs. 3+4) (p=0.14), percentage of positive core biopsies (p=0.15), and pretreatment PSA (p=0.41) were not. Median EPE distance was 1.75mm (range, <1-15mm). The rates of EPE >5mm and EPE >3mm were 11% and 15%, respectively. The odds ratios for erMRI detection of any EPE and of EPE >5mm were 3.06 and 3.75, respectively. T-stage and EPE+ erMRI predict pathologic EPE in men with GS 7 prostate cancer. The ability of erMRI to detect EPE increases with increasing EPE distance. These findings may be useful in patient selection for prostate brachytherapy monotherapy.