Clinicopathological Features of Breast Cancer in Relation to Exposure of Cycling Reproductive Hormones: A Multicenter Retrospective Study of 14 731 Patients Diagnosed with Invasive Breast Cancer

BACKGROUND: The reproductive period for women begins at menarche and ends at menopause, representing the total time period of exposure to cycling reproductive hormones. The potential associations between clinicopathological features and exposure of cycling reproductive hormones has not been extensively studied. This retrospective study enrolled 14 731 patients diagnosed with invasive breast cancer and was designed to evaluate factors associated with the reproductive period on breast cancer type and patient outcomes. MATERIAL/METHODS: A total of 14 731 female breast cancer patients from the Western China Clinical Cooperation Group from January 1, 2008, to December 31, 2017, were enrolled. Unconditional logistic regression was performed to assess the associations between clinicopathological features and menarche age, menopause age, and reproductive years. The differences in risk factors between lower and higher number of reproductive years (<35 and ≥35 years) were examined with the chi-square test. RESULTS: First, patients with late menarche age were more likely to present with tumors of higher histological grade and larger size. Second, the findings suggested a higher likelihood of smaller tumor size in postmenopausal patients with a greater length of reproductive years. Conversely, higher histological grade was associated with this group of patients, compared with their counterparts with shorter reproductive years. Third, patients with luminal breast cancer with a greater length of reproductive years were more likely to present larger tumors. CONCLUSIONS: Our findings indicated that several clinicopathologic factors, including tumor size and histological grade, were associated with the length of reproductive years in patients diagnosed with breast cancer.