Colorectal cancer arises from abnormal growth of cells in the colon or rectum, typically beginning with benign polyps that can become malignant over years. It is one of the most common cancers worldwide and a major cause of cancer related death, yet it is also highly preventable and treatable when detected early.

Risk increases with age, especially after 50, and is influenced by genetic and environmental factors. Family history, inherited syndromes such as familial adenomatous polyposis and Lynch syndrome, inflammatory bowel disease, obesity, physical inactivity, alcohol, smoking, and diets high in red and processed meat all contribute to higher risk. Protective factors include regular physical activity, a diet rich in fiber, fruits, and vegetables, and maintaining a healthy weight.

Symptoms often appear late and can include blood in the stool, changes in bowel habits, abdominal pain, weight loss, and fatigue, but screening can detect precancerous polyps before symptoms arise. Screening options include stool based tests that detect hidden blood or DNA changes and endoscopic methods such as colonoscopy and sigmoidoscopy that allow visualization and removal of polyps.

Diagnosis relies on imaging, pathology, and staging to assess how far the cancer has spread. Treatment typically involves surgery, sometimes combined with chemotherapy, radiation therapy, and targeted or immunotherapy drugs for advanced disease. Prognosis depends strongly on stage at diagnosis, with early stage cancers having high survival rates.

Current research focuses on improving early detection through better biomarkers, optimizing screening strategies, and developing more precise, personalized treatments that target specific molecular characteristics of each tumor.