Endometrioid Carcinoma of the Ovary: Outcomes Compared to Serous Carcinoma After 10 Years of Follow-Up.

OBJECTIVES: The prognostic significance of endometrioid ovarian cancer is unclear. In this study we compared rates of overall survival (OS) and disease-free survival between patients with endometrioid and serous ovarian cancers using long-term follow-up data.

METHODS: We included patients with endometrioid or serous ovarian cancers diagnosed at a single regional cancer centre between 1988 and 2006. Data on baseline and treatment characteristics were collected retrospectively. We used multivariate Cox proportional hazard models to determine the independent effect of histology on death or recurrence, adjusting for age, tumour grade, primary cytoreductive surgery, year of diagnosis, adjuvant treatment, and stage.

RESULTS: Five hundred and thirty-three women with ovarian cancer were included in the study cohort; 98 (18.4%) had endometrioid histology and 435 (81.6%) serous histology. The five-year OS rate for women with endometrioid cancer was 80.6%, and for women with serous ovarian cancer, it was 35.0%. The 10-year OS rates were 68.4% and 18.4% for endometrioid and serous histology, respectively. After adjusting for confounders excluding stage, there was a significantly lower risk of death from endometrioid cancer compared to serous ovarian cancer (hazard ratio [HR] 0.41, 95% CI 0.26 to 0.66). However, the difference was no longer significant after adding tumour stage to the model (HR 0.74, 95% CI 0.45 to 1.24). We found similar results for the risk of recurrence (HR 0.41, 95% CI 0.27 to 0.62 with stage not included, compared to HR 0.77, 95% CI 0.49 to 1.21 with stage included).

CONCLUSION: In this large cohort, in comparison with women with serous ovarian cancer, women with endometrioid ovarian cancer presented at a younger age, had earlier stage disease, and had disease almost always confined to the pelvis. The earlier stage of presentation of endometrioid ovarian cancer resulted in improved five-year and 10-year OS rates compared to serous ovarian cancer.