[The Breast Cancer Cohort Study in Chinese Women: the methodology of population-based cohort and baseline characteristics].

Breast cancer has been the first cancer among women with the incidence increasing gradually. In September 2016, the Breast Cancer Cohort Study in Chinese Women (BCCS-CW) was initiated, aiming to establish a standardized and sharable breast cancer-specific cohort by integrating the existing cohort resource and improving the quality of follow-up. The BCCS-CW may provide a research basis and platform for the precision prevention and treatment of breast cancer in etiology identification, prevention, early diagnosis, treatment, and prognosis prediction. We conducted a population-based perspective cohort by questionnaire interview, anthropometry, biological specimens, breast ultrasound and mammography. The cohort was followed by using regional health surveillance and ad hoc survey. Finally, BCCS-CW included 112 118 women, in which 55 419 women completed the standardized investigation and blood specimens were collected from 54 304 women. The mean age of participants was 51.7 years old, 62.7% were overweight or obese, and 48.9% were menopausal. The BCCS-CW will provide population-based cohort resource and research platform for the precise prevention and treatment of breast cancer in Chinese women.