While we do not know the exact cause of most colorectal cancers, there are certain known risk factors that affect a person’s chance of getting the disease. Some risk factors, like smoking, can be controlled; others, such as a person’s age, cannot.
Risk factors you cannot change include: age – more than nine out of 10 people with colorectal cancer are at least 50 years old and having had polyps or colorectal cancer before.
Some types of polyps increase the risk of colorectal cancer, especially if they are large or if there are many of them. If you have had colorectal cancer, you are more likely to have new cancers start in other areas of your colon and rectum. The chances of this happening are greater if you had your first colorectal cancer when you were younger.
Another risk factor is having a history of bowel disease. Inflammatory bowel diseases, like ulcerative colitis and Crohn’s disease, increase the risk of colon cancer. In these diseases, the colon is inflamed over a long time. If you have one of these diseases, your doctor may want you to have colon screening testing more often.
If you have family history of colorectal cancer and have close relatives – parents, brothers/sisters, or children – who have had this cancer, your risk might be increased.
Some people (about 5 per cent to 10 per cent) who get colorectal cancer have gene changes (mutations) that cause the disease that are passed on by a parent. Often, these changes lead to cancer that occurs at a younger age than is common. It’s important to check your family medical history not just for colon cancer and polyps, but also for any other type of cancer linked to these changes. Doctors recommend that members of families with these gene changes begin screening at a younger age.
The two most common inherited syndromes linked with colorectal cancers are familial adenomatous polyposis (FAP) and hereditary non-polyposis colorectal cancer (HNPCC).
People with FAP typically get hundreds or thousands of polyps in their colon and rectum, most often in their teens or as early adults. Cancer often starts in one or more of these polyps as early as age 20. By age 40, almost all people with this disorder will have cancer if surgery to remove the colon is not done. About 1 per cent of all colorectal cancers are due to FAP.
Hereditary non-polyposis colon cancer (HNPCC), also known as Lynch syndrome, accounts for about 3 per cent to 5 per cent of all colorectal cancers. It can be caused by inherited changes in a number of different genes that normally help repair DNA damage.
The cancers that occur as a part of this syndrome also happen when people are fairly young. People with HNPCC may also have polyps, but they only have a few, not hundreds as in FAP. The lifetime risk of colorectal cancer in people with this condition may be as high as 80 per cent. Other cancers are also linked with HNPCC.
Some racial and ethnic groups such as African Americans and Jews of Eastern European descent (Ashkenazi Jews) have a higher colorectal cancer risk.
People with type 2 (most often non-insulin dependent) diabetes have an increased risk of getting colorectal cancer.
Some lifestyle-related factors have been linked to colorectal cancer, including certain types of diets.
A diet that is high in red meats, like beef, lamb, or liver, and processed meats, including hot dogs, bologna, and lunch meat, as well as eating meats cooked at high heat by frying, broiling, or grilling can increase colorectal cancer risk.
Heavy use of alcohol has also been linked to colorectal cancer.
Being very overweight increases a person’s risk of having and dying from colorectal cancer. Exercising more may help reduce your risk.
Most people know that smoking causes lung cancer, but long-time smoking also increases the risk of many other cancers, including colorectal cancer.
Being aware of your family history and risk factors for colon cancer along with the proper screenings can help lower your chances of developing colon cancer. Take control of your health and talk to your doctor about colon cancer.
Dr. Darley Solomon is a consultant general surgeon at Chrissie Tomlinson Memorial Hospital. March is Colorectal Cancers Awareness Month.