Initial Experience with Dual-Tracer Sentinel Lymph Node Mapping Using RI and ICG in Robot-Assisted Surgery for Early-Stage Endometrial Cancer: A Prospective Exploratory Study

Background/Objectives: Sentinel lymph node (SLN) biopsy is a minimally invasive alternative to systematic lymphadenectomy for endometrial cancer staging. However, optimization of SLN identification during robot-assisted surgery remains an important clinical issue. This prospective exploratory study evaluated the feasibility and mapping characteristics of dual-tracer SLN mapping combining radioisotope (RI) and indocyanine green (ICG) in robot-assisted surgery for clinical stage IA endometrial cancer. Methods: Ten patients with clinical stage IA endometrioid carcinoma (grade 1 or 2) who underwent robot-assisted surgery at our institution between June 2025 and March 2026 were prospectively enrolled. Technetium-99m phytate was injected cervically the day before surgery, followed by SPECT-CT imaging. ICG was administered intraoperatively. SLNs were identified using both RI mapping and near-infrared fluorescence imaging. All patients subsequently underwent pelvic lymphadenectomy. SLN detection rates, concordance between tracers, intraoperative findings, and perioperative outcomes were evaluated. Results: The SLN detection rate with the dual-tracer method was 100% (10/10). RI mapping alone achieved bilateral detection in 30% (3/10), whereas ICG fluorescence imaging identified SLNs in all patients (100%). All RI-positive SLNs were also identified by ICG fluorescence imaging. In several cases, multiple fluorescent lymph nodes were observed, and gamma-probe assessment aided intraoperative SLN selection. No lymph node metastases were identified. One Clavien–Dindo grade IIIa complication (pelvic hematoma requiring intervention) occurred. No adverse events related to ICG were observed. Conclusions: Dual-tracer SLN mapping using RI and ICG was feasible in robot-assisted surgery for clinical stage IA endometrial cancer. ICG fluorescence imaging provided sensitive lymphatic visualization, whereas RI mapping offered complementary information for intraoperative SLN identification in selected cases. Further prospective studies with larger cohorts are required to clarify the clinical utility of the dual-tracer approach.