Establishment of Novel Intraoperative Monitoring and Mapping Method for the Cavernous Nerve During Robot-assisted Radical Prostatectomy: Results of the Phase I/II, First-in-human, Feasibility Study

Abstract

Background: Potency preservation often does not meet expectation despite nerve-sparing prostatectomy.

Objective: To set the protocol for intraoperative cavernous nerve monitoring and mapping during robot-assisted radical prostatectomy (RARP), and to evaluate its safety and clinical feasibility.

Design, setting, and participants: A prospective phase I/II, feasibility study was performed. A total of 30 patients with prostate cancer who underwent RARP at a high-volume tertiary academic hospital were enrolled.

Surgical procedure: Pudendal somatosensory evoked potential, bulbocavernosus reflex, spontaneous corpus cavernosum electromyography (CC-EMG), median nerve stimulation evoked CC-EMG, and neurovascular bundle (NVB)-triggered CC-EMG with various stimulation protocols were assessed during conventional RARP under total intravenous anesthesia with controlled muscle relaxation.

Measurements: The primary endpoint was the completion rate of planned surgery and assessment. Adverse events, and erectile and urinary functions were evaluated within 1 yr. CC-EMGs were graded and correlated with functional outcomes.

Results and limitations: The completion rate was 100%. Only one patient experienced adverse events, which were not related to study intervention. Grades of CC-EMGs including NVB-triggered CC-EMG before prostate removal were associated with baseline five-item International Index of Erectile Function (IIEF-5) score (grades 0-1, 4.6±2.7; grade 2, 13.2±6.8; grades 3-4, 16.6±5.9; p=0.003). Furthermore, grades of CC-EMGs including NVB-triggered CC-EMG after prostate removal were significantly associated with potency recovery (grade 0, 12.5%; grade 1, 0%; grade 2, 33.3%; grades 3-4, 100% at 12 mo; p=0.005) and postoperative IIEF-5 scores at all evaluation time points (grades 0-1, 2.6±2.8; grade 2, 4.3±5.8; grades 3-4, 15.7±11.0 at 12 mo; p=0.003).

Conclusions: We successfully established the protocol for safe intraoperative cavernous nerve monitoring and mapping using CC-EMG during RARP. Its grades were well correlated with erectile function.

Patient summary: In this first-in-human feasibility study, we successfully established the protocol for safe intraoperative cavernous nerve monitoring and mapping method during robot-assisted radical prostatectomy. The results were significantly associated with erectile function. Evaluation of clinical efficacy to preserve potency seems worthy of further optimization and investigation in confirmatory clinical trials.

Keywords: Cavernous nerve; Electromyography; Erectile function; Intraoperative monitoring; Prostatectomy; Robotic surgery.