LAUSR

Premenopausal and postmenopausal breast cancers are considered different types. Thus, this study aimed to explore differences in risk factors, epidemiological features, clinicopathological features, and treatment modes of premenopausal breast cancer compared to postmenopausal patients in western China. This was a hospital‐based, retrospective, multicenter epidemiological study of patients with breast cancer. Using the Western China Clinical Cooperation Group database, we obtained the records of 15,389 female breast cancers between January 2010 and April 2017. These patients were divided into premenopausal and postmenopausal groups, and their risk factors, epidemiological feature, clinicopathological features, and treatment modes were compared. Chi‐square tests, t‐test, and the multivariate logistic regression analysis were applied for statistical analysis. A total of 8395 patients were categorized as premenopausal, and 6994 patients were categorized as postmenopausal. Their risk factors, epidemiological features, clinicopathological features, and treatment modes were compared. Premenopausal patients with breast cancer had a greater tumor diameter at diagnosis (P = 0.008); higher rates of estrogen receptor (ER) expression (P < 0.0001), progesterone receptor (PR) expression (P < 0.0001), negative human epidermal growth factor receptor 2 (HER2) expression (P = 0.015), and negative P53 expression (P < 0.0001); and higher proportions of receiving breast‐conserving surgery and breast reconstruction (P < 0.0001), chemotherapy (P < 0.0001), radiotherapy (P < 0.0001), and endocrine therapy (P < 0.0001). The ethnicity, age at menarche, marital status, number of pregnancies, and number of births were the risk factors for age at diagnosis of breast cancer before or after menopause in western China. We found that the fall in the fertility rate, early menarche age, married, and less breastfeeding might have increased the possibility of premenopausal breast cancer. Significant differences exist in the tumor size, hormone receptor state, HER2 expression, epidemiological features, and treatment modes between premenopausal and postmenopausal female breast cancer patients in western China. Its further implementation requires prospective clinical testing.