Introduction/Background*The first Swedish national guidelines for endometrial cancer (NGEC) recommended adequate staging with pelvic and paraaortic lymphadenectomy for patients with high-risk disease, including non-endometrioid endometrial cancer (EC). The recommended adjuvant oncological treatment protocol was chemotherapy to all non-endometrioid EC and radiotherapy only for those with stage IIIC. Before the NGEC, the stipulated surgery was solely hysterectomy and bilateral salpingectomy followed by adjuvant chemo-and radiotherapy to all non-endometrioid ECs. The aim of this study was to investigate the outcome in survival and recurrence of this shift in treatment strategy.

Methodology All women with non-endometrioid EC, defined as serous, clearcell, carcinosarcoma and undifferentiated, were identified through the Swedish Quality Registry for Gynecological Cancer in the western Sweden health care region (1.9 million inhabitants) between 2010-2017 where the NGEC were implemented in 2013. Recurrences were identified including location and relative survival (RS), overall survival (OS) and disease-free survival (DFS) were analysed .The cohort was divided according to treatment protocol before and after NGEC implementation and compared.

Result(s)*In total 401 patients were identified and after exclusion for neoadjuvant chemotherapy, palliative treatment and preoperative stage IV, the final study cohort consisted of 261 patients who underwent primary surgical treatment with no evidence of disease at start of follow-up. The cohort before NGEC implementation was 103 patients and 158 patients after. The total recurrence rate was 26% and 6% were localized only to vagina. The RS rate for all patients diagnosed with a recurrence was 14.1% (95%CI 7.7-26.0) compared to 92.8% (95%CI 85.7-100.5) with no recurrence. Both the RS and OS rates were significantly improved after implementation of the NGEC. The 5-year RS was 58.8% (95%CI 48.6-71.0) for treatment in the first period and 79.8% (95%CI 71.0-89.8) for the second period (p=0.005). The 5-year OS was 54.3% (95%CI 45.5-64.9) and 68.7% (95%CI 61.3-77.0) respectively (p=0.011).

Conclusion*In this populationbased study of a complete cohort of non-endometrioid ECs we conclude that adequate lymphnode staging followed by adjuvant chemotherapy to all patients and radiotherapy only to those with postive nodes is associated with superior survival compared to chemo-and radiotherapy to all regardless of lymphnode status.