Dr. Andrew Chan leads research in colorectal cancer prevention that synthesizes traditional epidemiologic methods with novel genetic, biochemical, and intratumoral molecular markers to elucidate the underlying mechanisms mediating associations among diet, lifestyle, and tumorigenesis. His most substantial contributions have been in the field of chemoprevention. His early studies were referenced as high-quality evidence for U.S. Preventive Services Task Force recommendations on the use of aspirin and NSAIDs in the primary prevention of colorectal cancer. In the New England Journal of Medicine, he and his colleagues were the first to show in a human population that the reduction in risk of colorectal cancer associated with aspirin use was mediated through the COX-2 pathway. The American Society of Clinical Oncology heralded this work as one of the 18 most notable advances in cancer research of 2007. More recently, his group demonstrated that regular aspirin use after colorectal cancer diagnosis was associated with improved survival, particularly among cancers defined by COX-2 (JAMA 2009) or PIK3CA status (NEJM 2012). A commentary accompanying his JAMA publication declared, “in the near future . . . aspirin may become standard adjuvant therapy in the management of colorectal cancer.” In addition to his work in colorectal cancer, Dr. Chan has been instrumental in the development of one of the largest prospective cohorts of incident Crohn’s disease and ulcerative colitis, which has yielded seminal observations about lifestyle and dietary determinants of these conditions. Dr. Chan also leads a large prospective cohort collaborative of studies examining lifestyle and genetic risk factors for gastrointestinal bleeding.