Abstract B022: Conversion from minimally invasive surgical approaches to open surgery among endometrial cancer patients in a national cancer patients’ registry

Abstract Endometrial cancer (EC) ranks as the predominant gynecological malignancy in the US. While minimally invasive surgical (MIS) techniques have revolutionized EC management, conversion to laparotomy remains a concern, with reported rates varying widely. Factors influencing this conversion, including patient characteristics and tumor attributes, have not been fully understood. Addressing this gap, our study employs a national registry to analyze patient, tumor, and surgeon-related factors contributing to the transition from MIS to laparotomy in EC cases. Results: 0ur results showed, 3. 4% (135/4028) experienced planned MIS-to-open conversion. Demographic disparities were absent between conversion and MIS groups. Conversion was more prevalent in obese (29%) and morbidly obese (37%) patients (P=0. 04), linked to prior abdominal surgery (63% vs 52%; P=0. 001). Endometrioid EC predominated (59%) in the converted group, with higher non-endometrioid rates (serous carcinoma 16%, clear cell carcinoma 4%, carcinosarcoma 5%, mixed histology 12%; all P0. 01). Advanced FIGO stages were more common in conversions (stage II: 5%, stage III: 25%, stage IV: 9%; all P0. 001). Type II (24%) and type III (5%) hysterectomies were more frequent in conversions (P0. 001). Logistic regression indicated BMI, prior surgery, FIGO stage, histology, and operation type affected conversion (p0. 001), explaining 12. 3% of variance. Indications for conversion included uterine size, adhesions, and disease extent. Conclusion: the adoption of minimally invasive surgery (MIS) has become increasingly popular for managing endometrial cancer (EC), attributed to enhanced perioperative outcomes. However, prudent patient selection and surgical planning are imperative to mitigate the risk of unplanned transition to open surgery. Predictive factors for such conversion include uterine size, prior abdominal surgeries, surgical complexity, disease extent, and histologic types. Further prospective research is warranted to validate these findings and identify individuals at conversion risk. Ultimately, a personalized surgical approach, tailored to individual patient attributes, remains pivotal for optimizing outcomes in EC management. Citation Format: Abdelrahman Yousif, Julie Ngo, Deena Abdel-Gadir, Jenny Lachance, Benjamin Mize, Ilana Chefetz. Conversion from minimally invasive surgical approaches to open surgery among endometrial cancer patients in a national cancer patients’ registry abstract. In: Proceedings of the AACR Special Conference on Endometrial Cancer: Transforming Care through Science; 2023 Nov 16-18; Boston, Massachusetts. Philadelphia (PA): AACR; Clin Cancer Res 2024;30 (5Suppl): Abstract nr B022.