Peng LC, Mian OY, Lakshminarayanan P, et al. - The Sexual Health Inventory for Men (SHIM) instrument was administered for 115 stage cT1-T2 prostate cancer patients treated with Pd-103 brachytherapy over a 10-year interval by the experts in order to investigate associations between dose to periprostatic anatomic structures and erectile dysfunction (ED) outcomes in an institutional cohort treated with prostate brachytherapy. The sub-apical region (SAR) caudal to the prostate was the only defined region with dose-volume histograms parameters important for potency outcomes, on univariate analysis. Regression tree analysis classified patients into low ED risk, medium ED risk, and high ED risk groups. A dose of ≥ 72.75 Gy to 20% of the SAR with 1 cm expansion was most ominous for a 2-year potency outcome, in patients with good baseline function (SHIM ≥ 17). On multivariate analysis, the regression tree risk group continued to be important for prognosticating potency outcomes even subsequent to adjustment for baseline SHIM and age. Thus, in patients with good baseline function, the dose to the sub-apical region immediately caudal to the prostate was ominous for potency outcomes. Moreover, the minimization of dose to this region may enhance potency outcomes after prostate brachytherapy.