Ask an expert: Am I at risk for colorectal cancer? What can I do to lower my risk?

Everyone is at some risk for developing cancer of the colon or rectum, collectively known as colorectal cancer. And everyone can take steps to reduce his or her risk. In fact, about 90 percent of colorectal cancers may be preventable.

In the United States, the average lifetime risk of developing colorectal cancer is about 5 percent, or one in 20. You may be at higher risk if one or more of the following factors apply to you:

You have had colorectal cancer before

People who have already had colorectal cancer are at higher risk of developing a new cancer in another part of their colon. They also are at risk of their treated cancer coming back in another part of their body – most often in the liver or lungs.

You have had colon polyps removed

Having polyps in the past means that you are at higher risk of developing more polyps in the future. If undetected for several years, some of those polyps could turn into cancer. A history of fairly large polyps – those measuring at least 1 centimeter (a little less than half an inch) – increases your relative risk three- to six-fold, from the average of 5 percent to 15-30 percent.

You have a first-degree relative with polyps or colon cancer

If someone in your immediate family – your mother, father, sister or brother – has had polyps or colorectal cancer, your relative risk rises about two-fold, to 10 percent.

You have inflammatory bowel disease

Inflammatory bowel disease increases the relative risk of developing colorectal cancer three- to 15-fold, depending on how much of the colon is affected. Over time, chronic inflammation can make the immune cells in the affected part of the colon lose their ability to recognize cancers, allowing them to grow unchecked.

You have an inherited condition that causes colon cancer

Two rare hereditary conditions can cause gene defects that increase the risk of colorectal cancer dramatically. Familial adenomatous polyposis, or FAP, causes colon cancer in nearly 100 percent of people who have it – most often before age 45; hereditary nonpolyposis colorectal cancer, or HNPCC (also called Lynch syndrome), causes colorectal cancer in about 70 percent of people who have it. If one of your parents has tested positive for either of these after a colorectal cancer diagnosis, you have a 50 percent chance of having the gene defect, too. Providence’s Cancer Risk Assessment and Prevention Program can help you understand your risks and preventive options and decide whether genetic testing is appropriate for you.

You are African American

Colon cancer rates are higher among African Americans than among Caucasians. In addition, African Americans tend to develop colorectal cancers at an earlier age, and their cancers have a higher chance of being more advanced or life-threatening.

You are over age 50

About 90 percent of colorectal cancers occur after the age of 50; the risk increases with advancing age.

You smoke, you’re overweight or you don’t exercise

Smoking tobacco, obesity and inactivity are all associated with a higher risk of developing colon cancer.

What can you do to lower your risk?

Research makes it very clear that these four protective steps can greatly reduce the risk of developing colorectal cancer for most people:

  1. Get screened.
    Screening is the most effective way to prevent colorectal cancer. Colonoscopy – a screening that most people need only once every 10 years – has the potential to reduce your risk by 77 percent by finding and removing pre-cancerous polyps before they become cancerous. There are other ways to get screened, too – talk to your doctor about all of the options. Most people should start screening at age 50, but people with some of the higher-risk factors may be advised to start earlier.
  2. Get moving.
    Getting regular exercise – about 30 minutes on most days of the week – may lower your risk by 24 percent. Taking a brisk, rejuvenating walk a few times a week, or finding another sport or activity that you enjoy doing regularly, could make all the difference.
  3. Get back to a healthy weight.
    Studies strongly suggest that controlling body weight lowers the risk of colorectal cancer. If you’re carrying extra pounds, losing even a few can help. Forget about diets – read this Providence dietitian’s expert advice on losing the first 20 pounds.
  4. Get serious about quitting smoking.
    Smoking cigarettes is a proven cause of colorectal cancer. Talk to your doctor about medications and support programs that will give you the best chance of quitting for good.