252 Type of sentinel lymph nodes metastases and oncologic outcomes in endometrial cancer patients: an italian multi-institutional study

Introduction/Background* The role of volume of sentinel lymph nodes (SLNs) disease (macro-micrometastases and ITCs) in endometrial cancer is not clearly defined. We aimed to asses predictive factors for SLNs involvement and recurrence free survival (RFS) in patients with endometrial cancer. Methodology A multicenter retrospective evaluation of endometrial cancer patients with positive (macro-micro metastases or ITCs) SLNs, treated between 2003 and 2020, was performed. Predictive factors for nodal involvement (endometrioid vs non-endometrioid histology, grading, lymphovascular-space invasion (LVSI), myometrial invasion (MI), cervical stromal invasion, ESGO/ESTRO/ESP risk group), adjuvant therapy and oncological outcomes were evaluated. Result(s)* 142 patients were identified among 12 participating centers performing SLN mapping. In 64.8% of cases a low-volume disease (≤2 mm) was found in SLNs: 33 (23.2%) ITCs and 59 (41.6%) micrometastases. Factors influencing volume of nodal metastases were: grading [p:0.002] (G1 associated with low-volume disease), LVSI [p:0.007] and MI >50% [p:0.008] (both associated with macrometastases). There were: 20 (14.1%) low-risk, 14 (9.8%) intermediate, 88 (62%) high-intermediate and 20 (14.1%) high-risk according to 2020-ESGO/ESTRO/ESP risk group (on uterus). 17 (18.5%) patients with low-volume disease (8 micrometastases and 9 ITCs) did not receive any adjuvant therapy. At a mean follow-up of 34.6 months (range 1 –215) months, 21 (14.8%) relapses were recorded, only one among patients not receiving any adjuvant, none in the ESGO/ESTRO/ESP low risk group. The RFS at 2-years for the micrometastatic patients was 91%, similar to ITCs patients (79.1%), regardless of adjuvant treatment, but statistically better than patients with macrometastases (72.3%) [p: 0.026]. There was a trend to distinct RFS according to ESGO/ESTRO/ESP risk group, but none of the comparisons reached significance. The only factors affecting RFS were deep MI [p:0.03] and cervical stromal invasion [p:0.046]. Conclusion* More than half of patients with positive SLNs had low-volume disease. Grading, MI and LVSI predicted volume of nodal metastases. MI and cervical invasion affected RFS; while adjuvant treatment did not seem significantly associated with RFS in patients with low-volume disease. Longer follow-up time and a larger sample size are needed to understand the role of adjuvant therapy in low-volume metastatic SLNs.