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.