Abstract
BACKGROUND: Endometrial cancer (EC) often occurs subsequently to a primary cancer arising from a different site. However, little is known regarding the survival experience of EC as a second primary (ECSP) malignancy, specifically in relation to the original primary site and prior treatment. METHODS: Using Florida's cancer registry, all EC cases (first, second, or higher-order) diagnosed from 2005-2016 were analyzed. Kaplan-Meier methods and Cox Regression were used in a cause-specific survival analysis. RESULTS: A total of 2879 clinically independent ECSPs and 42,714 first primary ECs were analyzed. The most common first primary sites for ECSPs were breast cancer (BC) (n = 1422) and colorectal cancer (CRC) (n = 359). Five-year cause-specific survival was 84.0% (95% CI: 83.6-84.3) for first primary ECs and 81.8% (95% CI: 80.0-83.4) for ECSPs. After adjusting for age, race/ethnicity, histology, and stage at diagnosis, ECSPs had a lower risk of EC mortality than first primary ECs (hazard ratios [HR] 0.88, 95% CI: 0.79-0.97). ECSPs with a first primary CRC had a higher risk of EC-specific death (HR 1.47, 95% CI: 1.04-2.06) compared to ECSPs that followed BC in multivariable analysis. Finally, women who had chemotherapy for ECSP and preceding BC did not have a higher risk of death (HR 0.80, 95% CI: 0.49-1.31) compared to those who only received chemotherapy for first primary EC. CONCLUSIONS: ECSPs present a complex clinical profile. ECSP survival is superior to that of first primary EC. However, ECSPs following CRC may constitute a population of interest for their worse prognosis. Chemotherapy for a previous BC does not seem to impact the effectiveness of chemotherapy for ECs.