Risk Factors for Colorectal Cancer, including Early Onset

Colorectal cancer (CRC) arises from genetic, environmental, and lifestyle factors. Recognizing these risks helps clinicians identify high-risk patients and guide prevention. Risk factors are grouped as nonmodifiable (age, family history, race/ethnicity, prior abdominal/pelvic radiation, or inflammatory bowel disease) and modifiable (obesity, diet, inactivity, alcohol, or tobacco). The growing incidence of early-onset CRC (diagnosed before 50) is a particular concern and highlighted throughout this section.