Prevention and Screening for Colorectal Cancer

Lynn Butterly

Colorectal cancer is one of the few cancers we can actually prevent. Lynn Butterly, MD, a gastroenterologist and researcher at Norris Cotton Cancer Center talks about the importance of prevention and screening for colorectal cancer.

Why is screening for colorectal cancer in particular important?

Dr. Butterly - Colorectal cancer is the second leading cause of cancer death in the U.S. and one of the few that are actually preventable through screening. We make the distinction when we do screening between prevention and early detection. Prevention means we prevent an individual from ever developing colorectal cancer at all. Early detection means that we find the cancer early so that treatment is more effective and survival is better. For those reasons, it’s much better if cancer is detected early.

How are we able to prevent colorectal cancer?

Dr. Butterly - Almost all colorectal cancers start off as a little growth on the lining inside the colon called a polyp. Over 10 or 15 years, some of the polyps develop into colon cancer. That means that if we do a colonoscopy within that time, look inside the colon, find a polyp and remove it, we’ve eliminated any chance of that polyp from ever turning into cancer. That’s what makes colorectal cancer different than other cancers, is that we can actually prevent it from happening rather than just catching it early.

Is everyone at the same risk for developing colorectal cancer?

Dr. Butterly - Everyone is not at the same level of risk for colorectal cancer. The two common categories we might think about other than those who are at high risk due to hereditary diseases, would be average-risk individuals and increased-risk-individuals.  Average risk means people who have no symptoms, who are age 50, and have no personal history of colorectal cancer or potentially precancerous polyps. Increased risk means a greater chance of developing polyps or cancer. That’s because they either have a family history, particularly in a close relative, or, they have had a personal history of polyps or colorectal cancer. We test those with increased risk more often using colonoscopy because we know there’s a greater chance of finding colorectal polyps. This is called surveillance. For those who are at average risk, we generally begin screening at age 50, and have a choice of options that are effective at trying to prevent the growth of polyps or letting polyps turn into cancer. Anyone at average risk would want to talk with their provider about which option is right for them.

How often are polyps found during screening?

Dr. Butterly - I think what’s important to realize, is that when we do screening on people who are at average risk, we almost never find a colorectal cancer. It’s 0.1 to 0.2 percent of the time, which means we do thousands of colonoscopies and find maybe a handful of people already have colon cancer. It’s not impossible, but extremely rare. However, we are fairly likely to find polyps, because many people, 40 to 50 percent at least, have them.  Some of these polyps could turn into colorectal cancer. So we do a colonoscopy, find the polyps and remove them using a completely painless procedure. This eliminates the chance for them to develop into cancer.

Is there anything other than screening that people can do to prevent colorectal cancer?

Dr. Butterly - Absolutely. As with every other form of cancer, it’s important to lead a healthy lifestyle. Leading the list are not smoking, maintaining a healthy weight and getting exercise. All of the things that keep us healthy in our general lives are also important in preventing colorectal cancer. But in addition to that, it’s very important to talk about colorectal cancer screening with your provider. As we said, getting screened gives us the opportunity to actually prevent colorectal cancer, and that is critical in saving lives and keeping people from getting a disease that they don’t have to get.

To learn more about the importance of colorectal cancer screening and what to expect during a colonoscopy, please visit