Breast Cancer Risk Factors in Patients With Endometriosis

Background: Endometriosis is a common chronic inflammatory, estrogen-dependent disease with characteristics similar to cancer. Epidemiological studies of the association between endometriosis and breast cancer have yielded inconsistent results. The present study aimed to investigate the association between endometriosis and breast cancer risk factors. Methods: This case-control study (with 222 persons in each group) was conducted in Arash Women's Hospital from 2014 to 2017. Women with laparoscopically proven endometriosis were considered as cases. Controls were selected from women who had previous laparoscopic surgery due to any reason, and the absence of endometriosis was confirmed in them. Results: Multivariate logistic regression analysis by considering the risk factors (age, body mass index, gravidity, age at first pregnancy, age at menarche, history of breast-feeding, history of oral contraceptive and hormone use, history of miscarriage and induced abortion, breast cancer in first-degree relatives, and physical activity) revealed that endometriosis was positively association with age at first pregnancy (OR = 1.16, 95% CI: 1.08-1.25; P < 0.001), history of oral contraceptive use (OR = 3.91, 95% CI: 1.92-7.95; P <0.001), and history of hormone use (OR = 5.82, 95% CI: 2.70-12.56; P <0.001), and negatively associated with gravidity (OR = 0.61, 95% CI: 0.42-0.91; P = 0.01), and history of breast-feeding (OR = 0.37, 95% CI: 0.16-0.86; P = 0.02). Conclusion: Women with endometriosis have some of the breast cancer risk factors in their history, and these risk factors (gravidity, age at first pregnancy, history of breast-feeding, and OCP or hormone use) can change the risk of endometriosis as they increase or decrease the risk of breast cancer.