Significance of erection hardness score as a diagnostic tool to assess erectile function recovery in Japanese men after robot-assisted radical prostatectomy

The objective of this study was to characterize time-dependent recovery of erectile function in Japanese patients following robot-assisted radical prostatectomy (RARP) using the erection hardness score (EHS). This study prospectively included 170 Japanese patients with localized prostate cancer (PC) undergoing RARP without neoadjuvant hormonal therapy. The erectile function of each patient was assessed based on the International Index of Erectile Function-5 (IIEF-5) and EHS at the baseline and on every visit to an outpatient clinic after RARP. In this series, potency was defined as the ability to have an erection sufficient for intercourse, corresponding to EHS ≥3, while patients with EHS ≥2 were regarded as those with erectile function. Of these 170 patients, 20 and 75 underwent bilateral and unilateral nerve-sparing procedures, respectively; however, non-nerve-sparing procedures were performed in the remaining 75. A proportional increase in the IIEF-5 score according to EHS was noted at 24 months after RARP. At 6, 12 and 24 months after RARP, the recovery rates of erectile function were 11.9, 21.7 and 35.8 %, respectively, while those of potency were 3.8, 9.8 and 13.7 %, respectively. Of several factors examined, the age, preoperative IIEF-5 score and nerve-sparing procedure were identified as independent predictors of erectile function recovery. These findings suggest that favorable erectile function recovery could not be achieved in Japanese PC patients even after the introduction of RARP; therefore, it might be preferable for such a cohort to use EHS rather than IIEF-5 as an assessment tool for the postoperative recovery of erectile function.