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A risk factor is anything that increases a person's chance of getting a disease such as cancer. Different cancers have different risk factors. For example, unprotected exposure to strong sunlight is a risk factor for skin cancer and smoking is a risk factor for cancers of the lungs, larynx, mouth, throat, esophagus, kidneys, bladder and several other organs. Researchers have identified several risk factors that increase a person's chance of developing colorectal cancer.

A family history of colorectal cancer: Relatives of colorectal cancer patients are also at increased risk for developing this disease. Some of these families may have a colorectal cancer syndrome. Sometimes, colorectal cancer may also seem to run in some families that do not have one of these syndromes. Accurate identification of people with these syndromes is important because their doctors will recommend specific measures to prevent cancer or find it as early as possible, when treatment is most successful. Some doctors recommend that all people with colorectal cancer have an evaluation of their family history of the disease. People with a family history suggesting a colorectal cancer syndrome may consider genetic counseling and, in some cases, genetic testing. The American Cancer Society recommends screening test schedules for people with increased colorectal cancer risk that differ from those generally recommended for people at average risk. For more information, speak with your doctor.

Familial colorectal cancer syndromes: The following conditions make it more likely that a family member could develop cancer. Familial adenomatous polyposis (FAP) is a hereditary condition that greatly increases a person's risk of developing colorectal cancer. People with this syndrome typically develop hundreds of polyps in the colon and rectum. Cancer nearly always develops in one or more of these polyps between the ages of 30 and 50 if preventive surgery is not done. Like FAP, Gardner's syndrome results in polyps and colorectal cancers that develop at a young age. It can also cause benign (not cancerous) tumors of the skin, soft connective tissue and bones. Hereditary nonpolyposis colon cancer (HNPCC) develops in people at a relatively young age without first having many polyps. Women with this condition also have an increased risk of developing cancer of the endometrium (lining of the upper part of the uterus).

A personal history of colorectal cancer: Even when a colorectal cancer has been completely removed, new cancers may develop in other areas of the colon and rectum.

A personal history of intestinal polyps: Some types of polyps (hyperplastic polyps and inflammatory polyps) do not increase the risk of colorectal cancer. Other types, such as adenomatous polyps, do increase the risk of colorectal cancer, especially if they are large or there are many of them.

A personal history of chronic inflammatory bowel disease: Chronic inflammatory bowel disease (ulcerative colitis or Crohn's colitis) is a condition in which the colon is inflamed over a long period of time and may have ulcers in its lining. This increases a person's risk of developing colon cancer, so starting colonoscopy earlier and doing this test more often (every 1 to 2 years is recommended).

Aging : About 90% of people found to have colorectal cancer are 50 years of age or older.

A diet mostly from animal sources: A diet that consists mostly of foods that are high in fat, especially from animal sources, can increase the risk of colorectal cancer. Instead, the American Cancer Society recommends choosing most of your foods from plant sources and limiting intake of high-fat foods such as those from animal sources. The ACS also recommends eating at least five servings of fruits and vegetables every day and six servings of other foods from plant sources such as breads, cereals, grain products, rice, pasta, or beans. Many fruits and vegetables contain substances that interfere with the process of cancer formation.

Physical inactivity: People who do not get at least a moderate degree of physical activity have an increased risk of developing colorectal cancer.

Obesity: Being very overweight increases a person's colorectal cancer risk. Having excess fat in the waist area increases this risk more than having the same amount of fat in the thighs or hips. Researchers suggest that the excess fat changes metabolism in a way that increases growth of cells in the colon and rectum, and that fat cells in the waist area have the largest impact on metabolism.


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