Colon and Rectal Cancers - Risk Factors

Risk Factors

Colorectal cancer is the third most common cancer in the U.S., with Americans facing a lifetime chance of 5.5 - 6% for this cancer. In 2005, colorectal cancer was expected to cause 145,290 new cases and 56,290 deaths in the United States. About 72% of cancers occur in the colon and 28% in the rectum.

Sex

The lifetime risk of cancer of the colon or rectum is 5.9% for men and 5.5% for women.

Age

Colorectal cancer risk increases with age. More than 90% of these cancers occur in people over age 50. The rate of colorectal cancer in patients under 20 years is less than 1 in 100,000 per year. At age 50 about one in 2,000 people per year will develop colorectal cancer. After age 65, this rate increases to almost 3 in 1,000.

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Ethnicity

African Americans have the highest risk of being diagnosed with, and dying from, colorectal cancer. Among Caucasians, Jews of Eastern European (Ashkenazi) descent have an elevated rate of colorectal cancer. Asian Americans/Pacific Islanders, Hispanics/Latinos, and American Indians/Alaska Natives have a lower risk than Caucasians. In all ethnic groups, men have a higher risk than women.

Family History

About 20 - 25% of colorectal cancers occur among people with a family history of the disease. (Seventy-five percent of cases are due to other causes.) People who have more than one first-degree relative (sibling or parent) with the disease are especially at high risk. The risk is even higher if the relative was diagnosed with colorectal cancer before the age of 60.

About 5 – 10% of patients with colorectal cancer have an inherited genetic abnormality that causes the disease. Genetic mutations associated with colorectal cancer include familial adenomatous polyposis (FAP) and hereditary nonpolyposis colorectal cancer (HNPCC).

Lifestyle Factors

The risks for colon cancer are far higher in industrialized nations than less developed countries. A Western lifestyle, being sedentary, smoking, and excess weight have all been associated with increased risk for colorectal cancer. (It should be noted, however, that about 75% of cases occur without a known predisposing factor.)

Dietary Factors. A diet high in red meat consumption increases the risk for colorectal cancer. Other types of animal protein (low-fat dairy products, fish, poultry) may decrease the risk of developing polyps and colorectal cancer. Studies on fruits, vegetables, and fiber are mixed. There is some evidence that diets very low in fruits and vegetables may increase the risk. In any case, eating a variety of fruits and vegetables should be part of a healthy diet.