Subcapsular prostate cancer: Identification with mpMRI and MRI/TRUS fusion-guided biopsy

52 Background: The subcapsular region is often under-sampled by standard 12-core transrectal ultrasound (TRUS) prostate biopsy. We retrospectively evaluated multi-parametric MRI (mpMRI) features of subcapsular prostate cancers (PCa) and their detection on MRI/TRUS fusion-guided biopsy (FgBx). Methods: All patients referred for 3T mpMRI and subsequent FgBx under an IRB-approved protocol from Jan 2010 to July 2014 were reviewed. Histologically confirmed subcapsular lesions (just inside the prostate capsule with capsular border length >> width) were identified. Impact of the FgBx on clinical management according to current National Comprehensive Cancer Network (NCCN) guidelines was evaluated, with prior status based on outside TRUS biopsy results. Results: Of 992 eligible patients, 33 had subcapsular prostate lesions on mpMRI. In this subpopulation, mean age, PSA, and prostate volume were 63 years (range 52-76), 8.4ng/mL (1.2-63), and 53 mL (12-125). The FgBx, consisting of targeted (TBx) and systematic (SBx) portions, confirmed PCa in 24 of 33 patients. Five cancers (21%) were only detected by TBx. The remaining 19 were diagnosed on both TBx and SBx, but in 5 of these 19 (26%), higher Gleason scores were found on TBx cores. The FgBx results more accurately classified patients’ NCCN risk scores, with 17 prior unknown or low risk PCa upgraded to higher risk scores (Table). Conclusions: Subcapsular lesions on mpMRI are rare but largely malignant. Most are found on 12-core SBx, but ~20% require TBx for diagnosis, and TBx more accurately grades >25% of the lesions. The FgBx may improve clinical management of patients with subcapsular PCa, since more aggressive cancer was found in 17 of 24 patients. [Table: see text] [Table: see text] [Table: see text]