The American Cancer Society's Cancer Prevention Study 3 (CPS-3): Recruitment, study design, and baseline characteristics.

<bold>Background: </bold>Prospective cohort studies contribute importantly to understanding the role of lifestyle, genetic, and other factors in chronic disease etiology.<bold>Methods: </bold>The American Cancer Society (ACS) recruited a new prospective cohort study, Cancer Prevention Study 3 (CPS-3), between 2006 and 2013 from 35 states and Puerto Rico. Enrollment took place primarily at ACS community events and at community enrollment "drives." At enrollment sites, participants completed a brief survey that included an informed consent, identifying information necessary for follow-up, and key exposure information. They also provided a waist measure and a nonfasting blood sample. Most participants also completed a more comprehensive baseline survey at home that included extensive medical, lifestyle, and other information. Participants will be followed for incident cancers through linkage with state cancer registries and for cause-specific mortality through linkage with the National Death Index.<bold>Results: </bold>In total, 303,682 participants were enrolled. Of these, 254,650 completed the baseline survey and are considered "fully" enrolled; they will be sent repeat surveys periodically for at least the next 20 years to update exposure information. The remaining participants (n = 49,032) will not be asked to update exposure information but will be followed for outcomes. Twenty-three percent of participants were men, 17.3% reported a race or ethnicity other than "white," and the median age at enrollment was 47 years.<bold>Conclusions: </bold>CPS-3 will be a valuable resource for studies of cancer and other outcomes because of its size; its diversity with respect to age, ethnicity, and geography; and the availability of blood samples and detailed questionnaire information collected over time. Cancer 2017;123:2014-2024. © 2017 American Cancer Society. [ABSTRACT FROM AUTHOR]