Risk Factors for Colorectal Cancer

The risk for developing colorectal cancer increases with age. Other risk factors include a positive family history, meat consumption, cigarette smoking and alcohol consumption. Certain factors have been associated with a decrease in risk, including a high vegetable intake, use of non steroidal anti-inflammatory drugs, hormone replacement therapy, and physical activity. The average person has a 1 in 18 chance of developing colorectal cancer during his or her lifetime. Below is a breakdown of colorectal cancer risk by selected age groups.
Probability of Developing Invasive CRC over Selected Age Intervals, US, 1994-1996

Gender Birth to 39 40 to 59 60 to 70 Birth to Death

Male 0.06% 0.85% 3.97% 5.64%

(1 in 1,579) (1 in 124) (1 in 29) (1 in 18)

Female 0.05% 0.67% 3.06% 5.55%

(1 in 1,947) (1 in 149) (1 in 33) (1 in 18)

Source: Smith, RA, Mettlin, CJ, Johnston, K and H Eyre. (2000). American Cancer Society guidelines for the early detection of cancer. CA A Cancer Journal for Clinicians, 50: 34-49.
In recent years, a number of factors have been linked to either an increase or decrease in colorectal cancer risk. Some risk factors are modifiable and others are not. Lack of physical activity has been shown to be the most consistent risk factor linked to an increased risk of colon cancer. As only 15% to 20% of all cases of colorectal cancer involve a hereditary component, this means that up to 75% of cases may be preventable through behavior changes.* The chart below shows the relative positive and negative effects of several risk factors. Those that are less than one have a protective effect, and those that are greater than one have a harmful effect.
Relative Risks of Select Risk Factors for Colorectal Cancer

To see chart, please click here.

Source: Harvard Report on Cancer Prevention, Cancer Causes and Control, 10: 167-180, 1999. * Kinzler KW & Vogelstein B: Lessons from hereditary colorectal cancer. Cell, 87:159-170, 1996.