What are the causes and risk factors of colon cancer?

Colorectal cancer is caused by a genetic mutation that likely occurs from environmental situations or an inherited process. Most commonly, previous personal history of polyps, family history and chronic inflammation from diseases such as ulcerative colitis or Crohn’s and smoking can increase risk.

The exact causes of colorectal cancer are unknown. However, research has shown that certain factors do indicate higher risk. These risk factors include being over age 50, colorectal polyps, family history and certain genetic alterations.

Colorectal cancer, also called colon cancer, is found in the colon or the rectum, and usually develops very slowly, over a period of years, from a precancerous polyp. A polyp is an abnormal growth of the tissue that lines the colon or rectum. The two main types of polyps are the adenomatous polyp and the hyperplastic polyp. An adenomatous polyp is a benign, precancerous growth that, if not removed, has the greatest risk of becoming cancer; a hyperplastic polyp is a benign growth with no potential to develop into cancer.

The exact causes of polyps are uncertain, but they appear to be caused by both inherited and lifestyle factors. Genetic factors may determine a person's susceptibility to the disease, whereas dietary and other lifestyle factors may determine which individuals at risk actually go on to form polyps (and later cancers). Diets high in fat and low in fruits and vegetables may increase the risk of polyps. Cigarette smoking, a sedentary lifestyle and obesity may also increase the risk.

Few studies have been able to show that modifying lifestyle can greatly reduce the risk of colon polyps or cancer. However, reducing dietary fat, increasing fiber, ensuring adequate vitamin and micro-nutrient intake and exercise may improve general health. Studies have shown that getting adequate calcium may reduce the risk of polyps.

Because colorectal cancer develops slowly, screening for the disease is especially important as it allows the doctor to locate and remove polyps before they turn into cancer. For individuals at average risk, the ASGE recommends colonoscopy screening beginning at age 50 and repeating the procedure every ten years after a normal exam. For individuals with a family history, screening should begin at age 40, or at an age as recommended by their doctor. Some experts suggest African-Americans begin screening at age 45.

Removal of an adenomatous polyp prevents that polyp from becoming cancerous, but the patient is still at risk to develop new polyps in the colon and will require more frequent follow-up exams. If the patient has a family history of colorectal cancer, the interval for their follow-up exam may be shortened. After a colonoscopy exam, the doctor will recommend when the patient should return for another colonoscopy.

Dr. Daniel Labow, MD
Surgical Oncologist

While doctors don't know the exact cause of colon cancer, they do know some of the risk factors. In this video, Daniel Labow, MD, an oncology surgeon at The Mount Sinai Medical Center, explains what can increase your risk of colon cancer.

Although there are a number of risk factors that can increase someone's chances for developing colon cancer, the actual cause of colon cancer is generally unknown. Something causes healthy cells to begin growing abnormally. In some people, these overgrown cell areas can become colon cancer.

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Doctors aren't really sure what causes colon cancer, or why some people get colon cancer and others don't. They do know that colon cancer is linked to lifestyle, diet, inactivity, and obesity.

Juliet Wilkinson
Oncology Nursing Specialist

Although we are getting closer, science still cannot predict exactly what causes colon cancer in one person, yet not another. We do know that there are a number of risk factors that increase your chances of getting colon cancer. These risk factors include genetic factors (things passed down through your family that you cannot change) as well as lifestyle factors (things you can change). Lifestyle factors may include obesity, a sedentary lifestyle, dietary considerations (such as excessive alcohol use or a diet high in fat and red meat) and smoking. Change what you can now, to decrease your risk of colon cancer tomorrow.

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Important: This content reflects information from various individuals and organizations and may offer alternative or opposing points of view. It should not be used for medical advice, diagnosis or treatment. As always, you should consult with your healthcare provider about your specific health needs.