The Effect of Subsequent Pregnancy on Prognosis in Young Breast Cancer Patients (≤35 Years Old) According to Hormone Receptor Status

PURPOSE: We aimed to examine the effect of pregnancy on prognosis in young breast cancer (YBC) patients with hormone receptor (HR) positive after surgery and the safety of interrupting endocrine therapy (ET). METHODS: A retrospective cohort study was performed in patients who became pregnant after BC surgery under the age of 35 and were matched (1:4) to nonpregnant patients from 2006 to 2014. The primary endpoints were disease-free survival (DFS) and overall survival (OS) in HR-positive BC patients, and the secondary endpoints were DFS and OS in HR-negative BC patients and the whole population. Subgroup analyses included the DFS of patients who became pregnant within 5 years after surgery and DFS according to the ET interval time (≤ 30 months v > 30 months) in the pregnant group. RESULTS: A total of 1323 YBC patients were collected in our study, which included 68 pregnant patients and 264 matched nonpregnant patients. There were no statistically significant differences in DFS and OS among HR-positive patients (P=0.657, P=0.250, respectively) and the whole population (P=0.058, P=0.152, respectively). A BC pregnancy interval ≤ 5 years showed a better DFS (P=0.042), and an ET interval ≤ 30 months had a worse DFS (P = 0.01). CONCLUSION: This study did not observe a worse prognosis in patients with HR-positive disease who became pregnant after BC surgery, and an ET interval less than 30 months in pregnant patients led to a worse outcome. Patients were able to become pregnant within 5 years after surgery.