Introduction/Background Endometrial cancer (EC) is the most common gynecological cancer in Europe with approximately 20% of patients being diagnosed in advanced stage (FIGO III-IV). Until now, only few studies exist for cytoreductive surgery (CRS) in advanced stage reporting of complete cytoreduction in 18–75% cases. Evidence for EC from large multicenter analyses data is missing and the indication for CRS is widely based on individual and/or institutional decision algorithms.

Methodology STREAM-I/AGO-OP.

11/ENGOT-en22 is a retrospective, non-interventional, multicenter study aiming to identify preoperative clinical and molecular selection criteria for CRS. Patients who underwent CRS for advanced or recurrent EC at participating centers between 01/2011 and 12/2020 will be included. Available tumor material from CRS will be collected for evaluation of molecular classification and translational research. A multiple logistic regression identifying predictive factors for complete resection at CRS will be established using a stepwise covariate selection in the full clinical dataset. Therefore, a sample size of 800 patients was calculated based on estimated complete resection rates and number of independent variables.

Results As a result of this analysis, STREAM-II is planned as a consecutive prospective, single-arm, non-interventional, multicenter trial validating the predictive score established within the present study. Following confirmation, STREAM-III is planned to be a randomized, multicenter phase III trial evaluating CRS in EC.

Conclusion STREAM-I represents the first step towards Level I evidence for CRS in EC by identifying patients who most likely benefit from a radical surgical approach. STREAM-I will provide information to develop consecutive trials prospectively evaluating the impact of CRS in EC (STREAM-II/-III).

Disclosures No direct conflict of interest for this surgical trial exists. Further relation to companies have been disclosed and uploaded.