Combination of aneuploidy and high S-phase fraction indicates increased risk of relapse in stage I endometrioid endometrial carcinoma

INTRODUCTION: Endometrioid endometrial carcinoma is a cancer type with generally excellent prognosis when diagnosed at an early stage, but there is a subset of patients with relapsing disease in spite of early diagnosis and surgical treatment. There is a need to find prognostic markers to identify these patients with increased risk of relapse. Depth of myometrial invasion, histological grade, and presence of lymphovascular invasion are known risk factors. DNA content (ploidy) and proliferation measured as S-phase fraction (SPF) have been discussed as prognostic markers but need additional evaluation. MATERIAL AND METHODS: We evaluated relapse-free survival (RFS) with respect to ploidy and SPF, which was analyzed by flow cytometry on fresh tumor tissue, in a cohort of 1001 women treated for stage I endometrioid endometrial carcinoma in northern Sweden during the period of 1993-2010, with a median follow up time of 12.0 years. Data were obtained from historical records. RESULTS: In simple analysis, both aneuploidy and high SPF were associated to increased risk of relapse with hazard ratios (HR) 2.37 (95% CI 1.52-3.70) and 1.94 (95% CI 1.24-3.02), respectively. Our data also confirmed stage, tumor grade, and ploidy as independent prognostic markers in an age adjusted cox regression multivariable analysis but we did not find SPF to contribute to prognosis. However, the combination of aneuploidy and high SPF identified a group of patients with increased risk of relapse, HR 2.02 (95% CI 1.19-3.44). CONCLUSION: In this study, which is the largest study of ploidy and SPF in stage I endometrioid endometrial carcinoma using fresh frozen tissue, aneuploidy was shown to be an independent prognostic marker. Furthermore, the combination of aneuploidy and high SPF could be used to identify patients with increased risk of relapse.