Endometrioid Ovarian Cancer Presents Earlier, Offers Better Survival Than Serous Carcinoma

Women with endometrioid ovarian cancer present at a younger age and with earlier stage disease than those with serous ovarian cancer, according to a new analysis. The earlier presentation resulted in better 5- and 10-year overall survival rates as well.

Endometrioid carcinoma accounts for about 20% of all epithelial ovarian cancers. “The prognostic significance of histologic subtype is controversial, given the relative rarity of histologic subtypes other than serous,” wrote study authors led by Lilian T. Gien, MD, MSc, of the University of Toronto.

The new study was a retrospective analysis of 533 women with ovarian cancer diagnosed at a single center between 1988 and 2006. Of those, 98 women (18.4%) had endometrioid histology, and 435 women (81.6%) had serous histology. Researchers compared these cohorts with regard to presentation, treatment, and survival; the results were published online ahead of print in the Journal of Obstetrics and Gynaecology Canada.

At the time of diagnosis, endometrioid patients were a median age of 50 years, compared with 58 years for serous patients (P < .001). They also presented at an earlier stage of disease, with 83.7% of endometrioid patients presenting with stage I or II vs only 13.8% of serous patients (P < .001).

Almost all endometrioid histology patients (98%) underwent surgery as their primary treatment, compared with 69% of serous patients (P < .001). Most serous patients (97.2%) received adjuvant chemotherapy, compared with 57.1% of endometrioid patients.

Recurrences were more common in serous patients, with 70.1% experiencing a recurrence during the study period compared with 31.6% of endometrioid patients. Among those who did recur, 48.4% of endometrioid patients had the recurrence within the pelvis alone, compared to only 17.9% of serous patients, in whom abdominal recurrences were more likely.

There were 361 total deaths over the median follow-up period of 9.1 years; 26 of the endometrioid patients died (29.6%), and 355 of the serous patients died (77%). The 5-year overall survival rate was 80.6% in women with endometrioid carcinoma, compared with 35% in those with serous disease. At 10 years, these rates were 68.4% and 18.4%, respectively.

On a multivariate analysis that adjusted for age at diagnosis, tumor grade, and treatment variables, the hazard ratio (HR) for death from endometrioid carcinoma compared to serous carcinoma was 0.41 (95% CI, 0.26–0.66; P < .001). When tumor stage was added to that model, the HR was no longer significant, at 0.74 (95% CI, 0.45–1.24; P = 0.26). Adding tumor stage to a model for recurrence risk also attenuated the result.

“This demonstrates that stage of disease at presentation has a profound effect on overall survival and disease-free survival,” the authors wrote, though they noted that it remains unknown exactly why the two histologies tend to present at different stages. “There is a need for further exploration of molecular markers and biologic pathways to better characterize the behavior of these rare histologic subtypes. This will allow us to develop targeted therapies, improve treatment strategies, and improve survival rates and control recurrences.”