735 IPT (inverse probability of treatment weighting) of operative outcomes after systematization of SLNB in EC 2014–2023

Introduction/Background The aim of this study is to compare surgical outcomes after the routine replacement of the lymphadenectomy technique by the SLNB technique. Methodology Observational cohort study performed between July 2014 and December 2023. A retrospective study was performed comparing the cohort of patients included in the prospective study We compare a prospective cohort women with EC and SLNB (Sentinel Lymph Node Biopsy) with dual cervical and transcervical fundal injection of ICG + lymphadenectomy in EC from July 2014 to December 2020 with another cohort of patients prospectively registered, but data collected retrospectively from January 2021 to December 2023 operated at Hospital Universitario Donostia, using the same SLNB technique with no lymphadenectomy. Pelvic and aortic SLNB was performed following our protocol looking for upper&lower parametrical pathways and infundibula-pelvic pathway. In order to, inverse probability of treatment weighting (IPTW) was used to minimize confounding biases derived from the absence of randomization and to be able to estimate the population mean effect, establishing a weight for each participant according to the baseline variables observed. Results We included 442 in the analysis, Surgical staging was performed by SLNB&lymphadenectomy in 328 women if high or intermediate risk preoperative risk factors, and only by SLNB in 114. There was a 45.5% reduction in the lymphadenectomy rates, a reduction of 0.97 days for days of hospitalization, an increase of 0.66 gr/dL of the levels of haemoglobin and an increase of detection rate for aortic, bilateral pelvic and Aortic&bilateral pelvic SLN of 12.4%, 16.3% and 14.9%. Conclusion Implementation of SLNB for EC achieves a very significant reduction in the number of days of hospital stay, number of lymphadenectomies and an increase of the hemoglobin levels. Once the technique is systematized all detection rates are improved and specially bilateral pelvic detection rate. Disclosures No disclosures