Study population
cancer, tumor, primary breast cancer, breast cancer
CANCER, TUMOR, BREAST CANCER
Women diagnosed with primary breast cancer at Fujian Medical University Union Hospital in southeast China between the ages of 18 and 90 years during the period from January 2013 to March 2016 were asked to participate in this study. The cancer diagnosis was provided and confirmed by two pathologists in Fujian Medical University Union Hospital, together with the information on estrogen receptor (ER) status and tumor stage. The healthy controls were selected from women who participated in opportunistic or organized health examinations in the same hospital during the corresponding period without history of cancer. We only collected information for those woman within age 18–90 years. From 2013 to 2016, a total of 1350 cases and 2053 controls were collected, after excluding participants with missing data, 1321 breast cancer patients and 2045 healthy controls were analyzed using a complete‐case approach. All the participants in this study were permanent residents in Fujian Province, southeast China. They answered a structured questionnaire during a face‐to‐face interview to gather comprehensive data on sociodemographic characteristics and possible breast cancer risk factors. The participants also donated blood for genotyping.