274 Oncologic outcomes in women with low-intermediate risk endometrial carcinoma

Introduction/Background Surgery for endometrial carcinoma in Norway is centralized, except for women with assumed low/intermediate-risk disease. Nodal assessment is not routinely performed in these women. We sought to compare oncologic outcomes between women with preoperative grade1 stage IA and stage IB (G1 IA/IB). Methodology All cases with preoperative G1 IA/IB referred to our center from 2006–2021 were evaluated for progression-free survival (PFS) and disease-specific survival (DSS). Results In total, 518 women were included. Of these, 21/518 (5%) women were >stage I and 68/518 (13%) had >G1 histology on final pathology. Women with discrepant stage or histology had significantly worse PFS; stage I vs >stage I (p<0.001), G1 vs >G1 (p=0.006). Of 435 women with G1 IA/IB on final pathology, 14% (51/358) preoperative stage IA were up-staged to IB postoperatively, and 52% (44/77) preoperative stage IB were down-staged to IA postoperatively. With a median follow-up time of 84 months, 5.5% (24) recurred, 15 with vaginal recurrence, 1 with pelvic recurrence, 3 with distant metastasis and 5 with multiple metastasis. In univariate analysis, preoperative stage IB, lympho-vascular space invasion and age ≥75 years were significantly related to increased risk of recurrence. Preoperative stage IB was significantly related to poorer DSS (p=0.008). In multivariate analysis, none of these variables were independent risk factor for recurrence. However, preoperative stage IB remained near significant for worse DSS (p= 0.059). Conclusion We demonstrate significant discrepancies between preoperative assessment and final pathology for histology and myoinvasion for women with assumed low-intermediate risk disease, as well as poorer prognosis for women with preoperative G1 stage IB compared to those with G1 stage IA. These findings support the notion that low-risk endometrial cancer is a postoperative diagnosis, and that comprehensive surgical staging including nodal assent should be performed in all G1 cancers. Disclosures Attached