Through this Funding Opportunity Announcement (FOA), the National Cancer Institute (NCI) invites applications for support of investigator-initiated studies addressing mechanisms by which bariatric surgery impacts cancer risk, and seeks to draw in talented scientists who study bariatric surgery to investigate its effects on cancer, rather than shorter term outcomes such as weight loss and diabetes. The goal of this FOA is to support proof of concept studies for feasibility and exploratory development. Feasibility must not have already been developed in the literature or with preliminary data. While unpublished data are not permitted, references and data from widely available preprints that have a Digital Object Identifier (DOI) are acceptable. Investigators who have generated unpublished preliminary data should submit a proposal to companion R01.