ROK study-C (Rainbow of KIBOU study-colorectum): a colorectal cancer survivor cohort study on food, nutrition, physical activity, psychosocial factors and its influences on colorectal cancer recurrence, survival and quality of life in Japan

BACKGROUND: Many studies have shown that lifestyle factors such as diet, physical activity are related to the incidence of cancer. However, there are few studies on the association between lifestyle factors and cancer prognosis. To investigate the influence of lifestyle factors and psychosocial factors on prognosis, we started a prospective study of women with breast cancer, the Rainbow of KIBOU study-Breast (ROK Study-B) in 2007. As of February 2018, more than 6300 women have been enrolled, thus making this one of the world’s largest cancer patient cohort studies. Based on the know-how obtained from this study, we started another new cohort study for colorectal cancer patient (ROK Study-C). METHODS: The ROK Study-C is a prospective observational study for colorectal cancer survivors at the National Cancer Center Hospital. Participants fill in several self-administrated questionnaires about lifestyle, psychosocial factors (including posttraumatic growth and benefit finding, support), and quality of life (QOL) 5 times in total: at diagnosis, 3 and 6 months, 1 and 5 years after surgery. CT-scans will be collected to assess body composition and obesity. We also use blood and cancer tissue from the Biobank. The primary endpoint is disease-free survival. The secondary endpoints are overall survival and health-related QOL. The planned sample size is 2000 and the follow-up period is 5 years after the last enrollment. DISCUSSION: Recruitment began in December 2015 and the study is still ongoing. The ROK Study-C will contribute to improvements in patient prognosis and yield important evidence for colorectal cancer survivorship.