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

Purpose: 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. Methods and Materials: We included patients with clinical stage T1c-T2c, GS. =. 7 (3. +. 4 or 4. +. 3), and prostate-specific antigen (PSA) <10. ng/mL who underwent pre-prostatectomy erMRI. We compared pathologic EPE findings with pretreatment factors. Results: One hundred seventy-one men were eligible for inclusion. Pretreatment characteristics were: median age. =. 60 years (42-76); median PSA 4.9. ng/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 1.75. mm (range, <1-15. mm). The rates of EPE >5. mm and EPE >3. mm were 11% and 15%, respectively. The odds ratios for erMRI detection of any EPE and of EPE >5. mm were 3.06 and 3.75, respectively. Conclusions: 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.