Breast Cancer Patients Are at Increased Risk of Developing Uterine Serous Cancer: Implications for Counseling - A SEER Analysis

Introduction: Several studies have investigated whether patients with prior breast cancer (BC) are at an increased risk for endometrial cancer (EC)/uterine serous cancer (USC). We aimed to study this relationship and analyze the effect of prior BC on the incidence and prognosis of USC patients. Methods: With permission of the Surveillance, Epidemiology, and End Results (SEER) program of the US National Cancer Institute, clinicopathological information of women diagnosed with BC and following USC were analyzed. The recorded data included age at diagnosis, stage of disease, cause of death, interval time between BC and USC diagnosis, and overall survival. Results: The SEER database included 10,021 patients with USC during the years 1975-2015. 698 (6.96%) of these patients had been previously diagnosed with BC. The incidence of USC in patients with BC history was 57 times higher than in women without BC history (p value <0.001). The incidence of USC did not differ between estrogen receptor (ER)-positive and ER-negative BC patients (p value 0.94). The mean survival of USC patients with previous BC history was 8 years (96 months, 95% CI: 85.7-106.2), shorter than in USC patients with no BC history, presenting a mean survival of 10.6 years (127 months, 95% CI: 124.0-130.8) (p value = 0.002). Conclusion: Our results highlight the relationship between BC and USC, suggesting an increased risk for USC among BC patients. This clinical association should be introduced to BC patients, and physicians should be alert to any EC presenting symptom in BC survivors.