Risk factors

Factors that may increase the risk of rectal cancer are the same as those that increase the risk of colon cancer. Colorectal cancer risk factors include:

• Older age. Colorectal cancer can be diagnosed at any age, but most people with this type of cancer are older than 50. The rates of colorectal cancer in people younger than 50 have been increasing, but doctors aren't sure why.
• African-American descent. People of African ancestry born in the United States have a greater risk of colorectal cancer than do people of European ancestry.
• A personal history of colorectal cancer or polyps. Your risk of colorectal cancer is higher if you've already had rectal cancer, colon cancer or adenomatous polyps.
• Inflammatory bowel disease. Chronic inflammatory diseases of the colon and rectum, such as ulcerative colitis and Crohn's disease, increase your risk of colorectal cancer.
• Inherited syndromes that increase rectal cancer risk. Genetic syndromes passed through generations of your family can increase your risk of colon and rectal cancer, including FAP and Lynch syndrome.
• Family history of colorectal cancer. You're more likely to develop colorectal cancer if you have a parent, sibling or child with colon or rectal cancer.
• Eating a diet low in vegetables. Colorectal cancer may be associated with a diet low in vegetables and high in red meat, particularly when the meat is charred or well done.
• Too little exercise. If you're inactive, you're more likely to develop colorectal cancer. Getting regular physical activity may reduce your risk of cancer.
• Diabetes. People with poorly controlled type 2 diabetes may have an increased risk of colorectal cancer.
• Obesity. Obese people have an increased risk of colorectal cancer when compared with people considered at a healthy weight.
• Smoking. People who smoke may have an increased risk of colorectal cancer.
• Drinking alcohol. Regularly drinking more than three alcoholic beverages a week may increase your risk of colorectal cancer.
• Radiation therapy for previous cancer. Radiation therapy directed at the abdomen to treat previous cancers may increase the risk of colorectal cancer.