Sentinel lymph node (SLN) biopsy is now standard of care in the surgical management of several cancers (such as breast, melanoma, and vulvar) particularly in clinical stage I disease. It promises to find occult metastatic disease, while minimizing morbidity for the patient by sparing them of a radical complete lymphadenectomy and the morbidity of lymphedema. The role of and extensiveness of lymphadenectomy for endometrial cancer is controversial. However, it may serve to better guide adjuvant therapy, particularly the addition of systemic therapy for those with metastatic disease.

SLN biopsy for endometrial cancer was initially described in large single institution specialist centers with retrospectively reported series. European sites produced multi-center results with comprehensively staged patients, (SENTI-ENDO), however, this study was underpowered to answer the question of accuracy of the technique in detecting metastatic disease. In this lecture we will discuss the results of the FIRES trial (Fluorescence Imaging for Robotic Endometrial cancer Sentinel lymph nodes), the largest multi-center clinical trial for endometrial cancer SLN mapping. It was developed to definitively address the false negative rate of the technique, and its statistical design was based on that of GOG 173 (which serves as the definitive accuracy study in vulvar cancer). It is closed for enrolment after meeting statistical endpoints.

18 surgeons across 10 US centers participated. SLN mapping was performed by cervical injection of ICG and all patients underwent completion lymphadenectomy. Negative SLN’s on H&E sections were ultrastaged with immunohistochemistry for cytokeratin. The trial was designed to yield a type 1 error rate of 0.05 and power of 0.8 if the true sensitivity is 90%.

359 patients received attempted SLN mapping. Pelvic lymphadenectomy was performed in 343 patients (96%) and PA lymphadenectomy in 199 patients (56%). 296 patients (82%) had successful mapping of at least one SLN. Bilateral SLN’s were identified in 116 of these patients (60%). A mean of 20 (range 0-61) total lymph nodes were removed per patient. 41 (11.4%) patients had stage IIIC disease, 36 of whom mapped a SLN. Nodal metastases were correctly identified in the SLN’s of 35 of these 36 cases yielding a sensitivity of 97.2% (95% CI 85, 100) and a NPV of 99.6% (95% CI 97.9, 100). The false negative rate is 0.4% (95% CI 0.0, 2.1).

SLN’s identified with ICG have a high degree of diagnostic accuracy in detecting endometrial cancer metastases. Patients undergoing SLN biopsy in the absence of complete lymphadenectomy should be counseled about the potential small risk for false negative results.