Colon and Rectal Cancers - Risk Factors

Highlights	Prevention	Radiation Treatment
Introduction	Diagnosis	Follow-up Testing
Causes	Staging	Treatment for Metastasized Colorectal Cancer
Symptoms	Prognosis	Resources
Risk Factors	Surgery	References
Dietary Factors	Medications

Risk Factors

Colorectal cancer is the fourth most common cancer in the US, with Americans facing a lifetime risk of 6% for this cancer. An estimated 147,000 people in the US are expected to be diagnosed with colon or rectal cancer in 2004.

Sex

The risks overall are equal in men and women, but men have a higher risk for rectal cancers and women for colon cancers.

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Age

The most important risk factor for colon cancer is getting older. More than 90% of these cancers occur in people over 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, and after age 65, this rate increases to almost 3 in 1,000.

Ethnicity

Compared to Caucasians, African Americans are at higher risk of colon (but not rectal) cancer. The highest risks are in men of African descent, particularly in the sub-Saharan region. Ashkenazi Jews, of Eastern Europe descent, also have a higher incidence of colorectal cancer.

Family History

About 25% of patients under 45 years old and 15% of everyone who develops colorectal cancer have a genetic risk. The average lifetime risk of developing colorectal cancer is approximately 2%. People who have a sibling or parent (first degree relative) who developed colorectal cancer have three times (6%) the lifetime risk of developing colorectal cancer. People who have a first degree relative who developed colorectal cancer before age 45 have an even higher, 10%, lifetime risk of developing colorectal cancer.

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. Studies indicate that diets low in fruits and vegetables and high in meats pose a risk for colon cancer. Research also indicates that diets rich in fruits and vegetables are protective against many cancers.

Alcohol and Smoking. Smoking may increase the risk for colon cancer, and drinking alcohol regularly appears to compound this risk. Nonsmokers who drink alcohol and have diets rich in vegetables and fruits do not seem to have an increased risk.