The Contractor, Westat conducts participant retention activities, as well as passive data collection for approximately 155,000 participants in the National Cancer Institute’s Prostate, Lung, Colorectal and Ovarian (PLCO) Cancer Screening Trial. Westat coordinates data linkages and is responsible for attaining and maintaining approvals with institutional review boards, cancer registries, the National Death Index (NDI), and the Centers for Medicare and Medicaid Services (CMS). Westat manages data transfers with various entities and processes the data for submission to a data repository. Westat continues participant retention activities primarily by sending out mailings, updating changes in address, and answering questions by phone, with any changes in status documented and managed in a study database. Additionally, Westat oversees similar activities with subcontracted cancer screening centers in the study.