National Colorectal Cancer Awareness Month is an annual celebration observed in the United States during the month of March, to increase awareness of colorectal cancer — the second deadliest cancer in the United States, behind only lung cancer. It is also one of the most common: this year alone, an estimated 154,270 people will be diagnosed with colorectal cancer, joining more than 1.5 million colorectal cancer patients and survivors living today. In fact, 1 in 24 people will be diagnosed with colorectal cancer in their lifetime.
What is colorectal cancer exactly, and how does it start?
Most colorectal cancers start as a growth on the inner lining of the colon or rectum. These growths are called polyps. Polyps are quite common, especially as you get older. Most polyps are benign, or noncancerous. Some types of polyps can change into cancer over time (usually over many years). The chance of a polyp turning into cancer depends on the type of polyp it is.
If cancer forms in a polyp, it can grow into the wall of the colon or rectum over time. The wall of the colon and rectum is made up of many layers. Colorectal cancer starts in the innermost layer (the mucosa) and can grow outward through some or all of the other layers. When cancer cells are in the wall, they can then grow into blood vessels or lymph vessels (tiny channels that carry away waste and fluid). From there, they can travel to nearby lymph nodes or to distant parts of the body.
The stage (extent of spread) of a colorectal cancer depends on how deeply it grows into the wall and if it has spread outside the colon or rectum. Most colorectal cancers are adenocarcinomas. These cancers start in cells that make mucus to lubricate the inside of the colon and rectum. When doctors talk about colorectal cancer, they're almost always talking about this type.
What are the risk factors for developing colorectal cancer?
Different cancers have different risk factors. Some risk factors, like smoking, can be changed. Others, like a person's age or family history of cancer, can't be changed. But having a risk factor, or even many, does not mean that you will get the disease. And some people who get the disease may not have any known risk factors.
Many lifestyle-related factors have been linked to colorectal cancer. In fact, more than half of all colorectal cancers are linked to risk factors that can be changed, including:
- Being overweight or obese. If you are overweight or obese, your risk of developing and dying from colorectal cancer is higher.
- Diabetes mellitus, Type 2. People with type 2 diabetes mellitus are more likely than people who don't to develop colorectal cancer. Researchers suspect that this higher risk may be due to high levels of insulin in people with diabetes mellitus.
- Diet. A long-term diet that's high in red meats (such as beef, pork, lamb, or liver) and processed meats (like hot dogs and some lunch meats) raises your colorectal cancer risk. Cooking meats at very high temperatures (frying, broiling, or grilling) creates chemicals that might raise your cancer risk. Having a low blood level of vitamin D may also increase your risk. A diet that includes plenty of fruits, vegetables, and whole grains, and that limits or avoids red and processed meats and sugary drinks can lower your risk.
- Smoking. Typically, we think of this as a risk factor primarily tied to lung cancer, but people who have smoked tobacco for a long time are more likely to develop and die from colorectal cancer than people who don't smoke. Smoking tobacco increases the risk for developing colon polyps.
- Alcohol use. Colorectal cancer has been linked to moderate to heavy alcohol use. Even light-to-moderate alcohol intake has been associated with some risk.
The good news is: Colorectal cancer is also one of the most preventable and treatable cancers when caught early with screening tests.
Screening is the process of looking for cancer or precancer in people who have no symptoms of the disease. Colonoscopy, a colorectal cancer screening test, can often find colorectal cancer early when it's small, hasn't spread, and might be easier to treat. And regular screening can even prevent colorectal cancer. A polyp can take as many as 10 to 15 years to develop into cancer. With a colonoscopy, doctors can find and remove polyps before they have the chance to turn into cancer. Colonoscopy is the 'gold standard' of colorectal cancer screenings. The American Cancer Society recommends that people at average risk of colorectal cancer start regular screening at age 45. People at higher risk might need to start earlier.
If colorectal cancer is highly preventable with screening and highly treatable when caught early, then why is colorectal cancer the second deadliest cancer in the U.S.?
It's a great question with a complicated answer. A lack of knowledge about prevention and limited access to screening has a lot to do with it, and a third of people who could get checked don't. A missed or delayed screening gives colorectal cancer a chance to grow and become more dangerous long before symptoms appear. This may be because they don't know that regular testing could save their lives from this disease, or due to things like cost and health insurance coverage issues.
It's never too early to talk to your health care provider about which tests might be good options for you. They can also help you check with your insurance provider about your coverage.
If you don't have a primary care physician, visit our 'Find a Doctor' webpage to find one near you and schedule an appointment today.