Impact of modifiable lifestyle factors on outcomes after breast cancer diagnosis: the Setouchi Breast Cancer Cohort Study.

The primary purpose of this large cohort study is to investigate the effects on breast cancer outcomes of modifiable lifestyle factors after breast cancer diagnosis. These factors include physical activity, smoking, alcohol consumption, obesity and weight gain after diagnosis, alternative medicine and dietary factors. Women diagnosed with Stage 0 to III breast cancer are eligible for participation to this study. Lifestyle, use of alternative medicine, psychosocial factors, reproductive factors and health-related quality of life will be assessed using a questionnaire at the time of breast cancer diagnosis (baseline), and 1, 2, 3 and 5 years after diagnosis. Clinical information and breast cancer outcomes will be obtained from a breast cancer database. The primary endpoint will be disease-free survival. Secondary endpoints are overall survival, health-related quality of life, breast cancer-related symptoms and adverse events. Patient recruitment commenced in February 2013. Enrollment of 2000 breast cancer patients is planned during the 5-year recruitment period. The concept of the study is described in this article.