1306 Molecular subgroups versus risk of sentinel lymph node metastases and recurrence in endometrial cancer

Introduction/Background Molecular classification of endometrial cancer (EC) can be used to stratify patients for prognosis and adjuvant treatment. Recent studies have shown that the risk of lymph node metastases (LNM) differs between the molecular subgroups. However, limited data exists on the type of LNM, i.e.: macrometastases, micrometastases and isolated tumor cells (ITCs) as determined by ultra-staging after sentinel lymph node (SLN), and the subsequent risks for location of recurrence. Therefore our aim is to investigate the risk of SLN metastasis subtype for the molecular subgroups and the impact on outcome. Methodology All patients were subsequently included with available preoperative tumor tissue that underwent SLN procedure at the Mayo Clinic, United States between 2013 and 2019. Patients were allocated into the four molecular subgroups: POLE-mutated, Micro Satellite Instable (MSI), TP53-mutated or the non-specific molecular profile (NSMP) group. LNM were classified according to the largest metastasis. Results Patients included in the study cohort (n=215) presented with 16 (7.4%) macrometastases, 10 (4.6%) micrometastases and 13 ITCs (6%). Most metastases (23.1%) were found in the TP53-mutated group. The largest proportion of macrometastases were found in the TP53-mutated group (14.4% versus 4–9%). Most ITCs were found in the MSI and NSMP group, respectively 6.9% and 7.2% versus 2.9% in the TP53 and none in the POLE group. Within the TP53 group, 20.6% had distant recurrences as opposed to the MSI and NSMP group with 13.2% and 5.3% of patients with distant recurrence and none in the POLE group (pConclusion This study showed the significant association of subtypes of LNM and location of recurrence within the molecular subgroups which could further aid risk stratification of EC patients. Disclosures None.