Objectives To assess the effects on relative survival of established and new prognostic factors in stage I–III grade 1–3 endometrioid endometrial carcinoma and in the subgroup of stage I grade 1–2.

Methods This was a population-based, retrospective study including all women (n=1113) in the western Swedish healthcare region diagnosed with International Federation of Gynecology and Obstetrics (FIGO) stage I–III grade 1–3 endometrioid endometrial carcinoma in 2006–2011. Histology, grade, stage, and age were prospectively reported to the regional clinical and national cancer registers. DNA ploidy and S-phase fraction were analyzed by flow cytometer. S-phase fraction cut-off was set at ≥8%. Tumor biopsies were classified as diploid if there was one G0/G1 peak or the DNA index was 1.0±0.04. Overexpression of p53 as determined by immunohistochemistry was positive if strong nuclear staining was found in >30% of the neoplastic cells.

Results Based on univariable statistical analyses we found that 5-year relative survival was significantly associated with S-phase fraction, DNA ploidy, p53, stage, grade, and age. Excess mortality for S-phase fraction ≥8%, aneuploidy, and p53 overexpression was 8, 14, and 8 and times higher, respectively. However, in a multivariable regression model, adjusted for stage, grade, and age, S-phase fraction, DNA ploidy, and p53 were not statistically independent prognostic factors (p=0.413, p=0.107, p=0.208, respectively) for 5-year relative survival in stage I–III grade 1–3 endometrioid endometrial carcinoma. In a subgroup analysis of stage I grade 1–2, aneuploidy identified a subgroup with impaired 5-year relative survival.

Conclusion We can conclude that S-phase fraction, DNA ploidy, and p53 overexpression did not improve identification of high-risk patients by stage, grade, and age in stage I–III endometrioid endometrial carcinoma. In stage I, aneuploidy and grade 2 predicted lower relative survival rates than other variables.