Colorectal Cancer Risks

Quick summary

Colorectal cancer is one of the most common cancers in older folks, and knowing your parent's risk is important because early detection is crucial to successful treatment. Age is the biggest risk factor for colorectal cancer; more than 90 percent of people diagnosed with it are over the age of 50. Make a list of the risks that apply to your parent, then use it to discuss colorectal cancer screening with your parent's doctor.

1. Smoking or chewing tobacco

If your parent smoked during his younger years, even if he quit at some point, he's more likely to get a host of cancers, including colorectal cancer -- not just lung cancer, as many people assume. In fact, research in the last few years has established a strong connection between smoking and colorectal cancer. A study published in Gastroenterology in February 2008 revealed that smoking doubles the risk of developing colorectal polyps, which experts have long suspected are the underlying cause of most colorectal cancers. The researchers came to the surprising conclusion that 20 to 25 percent of colorectal polyps may be attributed to smoking, and that the risk was significantly greater for high-risk polyps, suggesting that smoking may play an important role in causing polyps to develop into cancer.

2. History of digestive disorders

Polyps -- benign wartlike growths -- in the colon are the red flag doctors look for when screening for colorectal cancer, but other digestive conditions are risk factors as well. If your parent has suffered from ulcerative colitis, irritable bowel syndrome, or Crohn's disease, he's at increased risk of developing colorectal cancer due to chronic inflammation of the colon.

3. Family history of colon cancer

If any of your parent's immediate family members (parents, siblings, or children) had colorectal cancer, your parent is somewhat more likely to develop this disease himself. The likelihood goes up if more than one family member had colorectal cancer or if any of your parent's relatives developed the cancer before the age of 50.

4. Previous history of colorectal cancer

If your parent has already had colon cancer removed or treated, he's at increased risk for getting new tumors in other areas of the colon or rectum. This is particularly likely if his previous colon cancer diagnosis and treatment occurred prior to the age of 60. In addition, women who've had ovarian or endometrial cancer and men who've had testicular cancer are at higher risk for colon cancer. Men who've had radiation therapy for prostate cancer have an increased risk of rectal cancer.

5. A diet high in fat, low in nutrients

If your parent's diet has been heavy on red meat and low on vegetables and whole grains, this increases his risk of colorectal cancer. A diet high in animal fat has been linked with colon cancer, as has a diet low in calcium and folate. Eating at least five daily servings of fruits and vegetables protects against colon cancer.

6. Alcohol consumption

Drinking more than two alcoholic drinks a day has been linked to colorectal cancer. Drinking three or more alcoholic drinks a day substantially increases the risk.

7. Being African American

African Americans have the highest incidence of colorectal cancer, and whites come in second. Asians have a significantly lower incidence, and Hispanics and Native Americans are lowest of all, with close to half the incidence of colorectal cancer compared with whites and African Americans.

8. Genetic history

Between 3 and 5 percent of colorectal cancers are caused by an inherited genetic susceptibility to the disease; the most common of these is Lynch syndrome, or HNPCC (hereditary nonpolyposis colorectal cancer). A genetic mutation most common in people of Eastern European Jewish descent (also called Ashkenazi Jews) is also responsible for an increased risk of colon cancer.

9. Having diabetes

If your parent has diabetes, his risk of colorectal cancer is increased by 30 percent. Unfortunately, diabetes has also been linked to a worse prognosis for the cancer once it's detected and treated.

10. Being overweight or obese

Experts don't know why being overweight or obese is a risk factor for colorectal cancers, but statistical analyses prove that it is. One recent study showed that obese women were four times as likely to develop colon cancer as those whose body mass index was within the normal range. The risk is highest in those who are "apple shaped," carrying their excess fat around their bellies. The best guess is that it has to do with insulin levels, though researchers are still exploring this issue.