2\. 1. Selection of the Patients From June 2002 to August 2015, a total of 1,503 patients underwent RARP. During this period, perioperative data, including postoperative functional outcomes, were prospectively collected using a customized database; our ethics committee approved the data collection. Erectile function was assessed using the sexual health profile for men (SHIM) score at 3, 9, 15, and 24 months and then annually after surgery, and the duration of pad-free continence recovery was asked by a non-physician third party. In our institution, RH was applied during RARP for all patients from February 2008 to March 2015 (consecutively between the 671st and 1459th cases). Among the recruited patients, 789 men (52.6%) underwent HP, leaving the other 711 (47.4%) as controls.
The inclusion criteria for this study were as follows: (1) bilateral nerve-sparing RARP (over 70%) and (2) a minimum follow-up of 15 months. The exclusion criteria were as follows: (1) men with a history of salvage radiation therapy, chemotherapy, or hormone therapy after RARP (n=98) and (2) the presence of a high-risk disease with an initial prostate-specific antigen (PSA) level over 20 ng/ml or biopsy Gleason score over 8, which may influence the refining surgical plane around the neurovascular bundle (NVB), thereby affecting the degrees of nerve-sparing strategy at the time of surgery (n=275). Further, (3) the initial 100 cases were excluded to avoid potential bias from the learning period. From a cohort of 1,503 patients, 59 (3.92%) men whose potency outcome within 15 months was not assessed were also excluded from the study. Finally, 930 patients were selected for the analysis; half of the procedures (n=466, 50.1%) were performed under RH and the remaining other half (n=464, 49.9%) as normothermal controls.
2\. 2. Endpoints of the Study The primary endpoints of this study were the SHIM score and the rate of potency regain, which was defined as a SHIM score \>17 in the RH and control groups 15 months after surgery. Considering the proven impacts of age and preoperative SHIM scores on the recovery of potency, the groups were further divided into the young and potent (YP: age \<65 years and SHIM score ≥22, n=409, 43.9%) subgroup and susceptible for impotency (SI: age ≥65 years or SHIM score \<22, n=512, 55.1%) counterpart and investigated the sexual function of the YP subgroup. The secondary endpoints were the duration of pad-free continence regain and the rate of continence recovery within 3 months after surgery, especially in the YP subgroup.
2.3. Surgical Protocol for RH All procedures were performed by a single surgeon. RH was achieved by devising an endorectal cooling balloon system (ECB) as previously reported \[2, 4, 5\]. In brief, a 40-cm, 24-F, 3-way latex urethral catheter was placed inside a 5 × 2.5-inch elliptic latex balloon that distended at a low pressure and conformed to the rectal wall without excessive deformations. The lubricated ECB was inserted just inside the anus and anchored by inflating the catheter balloon to 20 ml. The ECB was then distended and cycled continuously with cold saline (4°C) by gravity 40 cm above the patient. The ECB volume was \~200 ml. A 9-F esophageal probe (Smiths Medical ASD, Rockland, MA) was used to obtain the intracorporeal temperature readings directly along the anterior surface of the rectum/NVB.
