Sentinel Node Mapping in High Risk Endometrial Cancer

Although most patients with endometrial cancer present with early-stage disease, the standard treatment still includes systematic lymph node dissection for staging. Recently, SLN mapping has emerged as an acceptable surgical strategy when deciding between complete lymphadenectomy and no node dissection. This approach can help avoid the morbidity that is associated with a complete lymphadenectomy, such as neurovascular injury, lymphocyst formation, and lymphedema. A recent meta-analysis that included 55 studies and 4915 patients reported an overall SLN detection rate of 81% versus 50% for bilateral SLNs. Moreover, the use of indocyanine green increased the bilateral SLN detection rate compared with blue dye (74.6% vs. 50.5%). Yet, the studies noted an overall sensitivity of 96% and false negative rates of less than 5% when analyzed per hemipelvis. Since 2014, the National Comprehensive Cancer Network (NCCN) guidelines have recommended SLN mapping as an alternative option for node staging in endometrial cancer. However, most studies on SLN mapping have included patients who are at low risk for lymph node involvement and thus might underestimate the false negative rate. Recently, Soliman et al. reported a series of only high-grade and deep invasive endometrial cancers for which patients underwent SLN mapping, followed by pelvic and para-aortic lymph node dissection. An 89% detection rate was reported, suggesting that SLN mapping accurately identifies node metastases, with an negative predictive value (NPV) of 98% and an false negative predictive value (FNPV) of 2% when analyzed by hemipelvises. Positive nodes were found in 22.8% of patients (43% of isolated tumor cells and micrometastases), and in 40% of cases, the SLN was the only positive node. Data from the investigators corroborate these findings-26.7% of high-risk cases had positive nodes (50% of isolated tumor cells and micrometastases), and when analyzed by hemipelvis, the NPV was 97.9% and the FNPV was 2.1%. In 14 (70%) patients, the SLN was the only positive node. Moreover, there are few publications that have compared the results of the addition of SLN mapping to lymphadenectomy alone. Raimond et al. compared 156 patients that had SLN mapping with 95 who had pelvic node dissection. In their study, SLN mapping and imuno-histochemistry (IHC) were performed in low- and intermediate-risk patients, and the former detected metastatic node 3 times more often than complete pelvic lymphadenectomy alone (16.2% vs. 5.1%, p=0.03). They had no false negatives, and the IHC findings modified the adjuvant therapy in half of all cases. Holloway et al. compared a series of 661 patients who had undergone pelvic and para-aortic lymphadenectomy with 119 who were subjected to SLN mapping plus node dissection, including 68 high-intermediate- and high-risk patients in the SLN mapping group (GOG99 stratification). Despite the similarity in demographics and pathological risk factors, the SLN group had more LN metastases that were detected (30.3% vs. 16.3%; p\<0.001) and received more adjuvant therapy (28.6% vs. 16.3%; p=0.003). The SLN was the only positive node in 18 (50%) of mapped cases, and the false negative rate was 2.8%.The investigators recently published a series on high risk endometrial cancer and also recorded a higher pelvic node metastasis rate for the SLN mapping group (26.7% vs. 14.3%, p=0.02) but no significant difference in para-aortic node metastases (13.5% vs. 5.6%, p=0.12). Notably, if considered only patients in whom SLNs were mapped, 31.3% had pelvic positive nodes. Despite the differences in uterine risk factors between groups, 10.6% (8/75) of patients in the SLN group had node metastasis that was diagnosed only after IHC. Excluding these patients, the SLN group would have had a node positivity rate of 17.3%, similar to the N-SLN group (17.4%), reinforcing the impact of IHC in the detection of node metastases. Moreover, the SLN group received more adjuvant chemotherapy (33.5% vs. 48%). The overall detection rate for SLNs was 85.3%, and bilateral SLNs were observed in 60%. The investigators noted an overall sensitivity of 90%, a negative predictive value of 95.7%, and a false negative predictive value of 4.3%. Recently, Touhami et al. showed that the risk of non-SLN metastasis is 61% when the SLN metastasis size is ≥2mm, and 5% for SLN metastasis of \<2mm. However, one of the remaining uncertainties is the role of systematic lymphadenectomy after a positive SLN. In other words, is there any benefit in favor of systematic lymphadenectomy in a patient that already undergo adjuvant chemotherapy? The investigators hypothesized that there is no disease free survival benefit in adding systematic lymphadenectomy to only sentinel node mapping and proposed a prospective randomized controlled non-inferiority trial comparing SLN mapping to SLN mapping with systematic lymphadenectomy in high risk endometrial cancer.