Performance of sentinel lymph node biopsy in high-risk endometrial cancer

OBJECTIVE To determine the rate and performance of sentinel lymph node (SLN) mapping among women with high-risk endometrial cancers. METHODS Patients diagnosed between 2012 and 2015 with uterine cancer of grade 3 endometrioid, clear cell, serous or carcinosarcoma histology and who underwent SLN mapping prior to full pelvic lymph node dissection were included. Subjects underwent methylene blue or ICG injection for laparoscopic (N = 16) or robotic-assisted laparoscopic (N = 20) staging. Outcomes included SLN mapping rates, SLN and non-SLN positive rates, false negative SLN algorithm rate, and the negative predictive value (NPV) of the SLN algorithm. Fisher's exact test was used to compare mapping and node positivity rates. RESULTS 9/36 (25%) patients with high-risk uterine cancer had at least one metastatic lymph node identified. Successful mapping occurred in 30/36 (83%) patients. SLN mapped to pelvic nodes bilaterally in 20 (56%), unilaterally in 9 (25%), and aortic nodes only in 1 (3%). Malignancy was identified in 14/95 (15%) of all sentinel nodes and 12/775 (1.5%) of all non-sentinel nodes (p < 0.001). The false negative rate of SLN mapping alone was 2/26 (7.7%); the NPV was 92.3%. When the SLN algorithm was applied retrospectively the false negative rate was 0/31 (0%); the NPV was 100%. CONCLUSION SLN mapping rates for high-risk cancers are slightly lower than in prior reports of lower risk cancers. The NPV of the SLN mapping alone is 92% and rises to 100% when the SLN algorithm is applied. Such results are acceptable and consistent with larger subsets of lower risk endometrial cancers.