Andrew T. Chan, MD, MPH is a leading epidemiologist and clinician-scientist at Massachusetts General Hospital and Harvard Medical School, where he serves as the Daniel K. Podolsky Professor of Medicine, Director of Cancer Epidemiology at the Mass General Brigham Cancer Institute, and Chief of the Clinical and Translational Epidemiology Unit. He is widely known for pioneering large-scale research into how lifestyle, diet, medications, and other exposures influence cancer risk and survival, particularly colorectal cancer, as well as broader gastrointestinal and metabolic health outcomes. Through his work using data from long-running prospective cohorts, Chan has helped clarify how common factors like aspirin use, dietary patterns, and early screening can meaningfully alter disease risk and long-term health across populations. His research bridges clinical insights with rigorous population science to inform prevention strategies and improve public health.