1043PCancer-specific survival with or without adjuvant chemotherapy in high-risk stage I endometrial cancer

Abstract Background Controversies exist for utility of adjuvant chemotherapy (AC) in early stage high risk endometrial cancer (EC). Our study sought to evaluate overall, relapse-free and cancer-specific survivals (OS, RFS, CSS) in patients with high risk FIGO stage I EC. Methods Per provincial guideline, high risk stage I EC eligible for AC was defined as 1) endometrioid histology, stage IB and grade 3 or 2) non-endometrioid histology with any myometrial invasion. We identified all consecutive patients with stage I EC from 6 cancer centres in British Columbia, Canada diagnosed between 2000 and 2010. CSS was defined as time between diagnosis and death due to endometrial cancer. Descriptive statistics were used to evaluate patient, disease and treatment characteristics; Cox proportional hazard regression was used to evaluate differences in OS, RFS and CSS. Results Among stage I EC (n = 1426), 24 with endometrioid histology and 214 with non-endometrioid histology with high risk characteristics were identified (n = 238). Median age was 66 (range 33-91); stage IA = 196, IB = 50; grade 1=16, 2=20, 3=196; LVI+ 88. Among all high risk patients, OS (RR 0.37, 95% CI 0.20-0.71, p = 0.002; median 6.3 vs 12.2 years) and RFS (RR 0.35, 95% CI 0.19-0.65, p = 0.001; median 5.6 vs 12.2 years) were significantly better in patients who received AC, but CSS (RR 0.65, 95% CI 0.32-1.33, p = 0.24; median not reached in both groups) was not statistically improved although numerically favoured AC. Similarly, among non-endometrioid histology, OS (RR 0.40, 95% CI 0.20-0.78, p = 0.008; median 6.4 vs 12.2 years) and RFS (RR 0.38, 95% CI 0.20-0.72, p = 0.03; median 5.9 vs 12.2 years) were significantly better in patients who received AC, but improvements in CSS with AC (RR 0.68, 95% CI 0.3-1.4, p = 0.32; median not reached in both groups) were not statistically significant. Conclusions Despite its use, there is insufficient evidence that AC reduces risk of death due to cancer in high risk stage I EC, although DSS is numerically improved in patients who received AC. Improvements in OS and RFS associated with chemotherapy may be largely attributed to other confounding factors. Future prospective studies are needed to clarify the role of contemporary AC in high risk stage I EC. Legal entity responsible for the study The authors. Funding Has not received any funding. Disclosure All authors have declared no conflicts of interest.