Most cases of colon and rectal cancer are now preventable.
In many Western countries, people over age 50 have routinely been offered screening tests that can prevent colon and rectal cancer from developing. As a result, the incidence rates of colon and rectal cancers, which are often referred to as “colon cancer”, have dropped dramatically.
However, in people under age 50 in the same countries, rates of colon and rectal cancer have been rapidly increasing.
How do screening tests prevent cancer from developing?
Colon cancers develop inside the colon or rectum from non-cancerous growths called polyps.
Once a polyp begins to grow, there is a one-in-ten chance that it will become cancerous. Fortunately, this usually takes ten or more years, making it possible to remove the polyp and prevent cancer from occurring.
Polyps can be removed during a cancer-screening test called a colonoscopy.
Why are rates of colon cancer rising so quickly in people under age 50?
Scientists are not sure why colon cancer is increasing in younger people. Yet ten years from now, the incidence of colon cancer in 20 – 34-year-olds in many Western, high-income countries is expected to be 90% higher than it is today.
Scientists don’t believe that the increase in screening rates over the last decades explains the higher rates of colon cancer in young adults. One reason is that the rates are rising fastest in the youngest adults, who are also the least likely to be screened.
Poor lifestyle choices probably don’t explain the increase either. Young adults today have poorer diets and less physical activity when compared with young adults of earlier generations. However, because young adults today smoke less and drink less alcohol, the overall impact from lifestyle choices is fairly similar.
What are the risk factors for developing colon cancer?
The major risk factors for colon cancer include:
Although the incidence of colon cancer is rising among younger people and has fallen among older people, older age is still one of the biggest risk factors. The median age for men at diagnosis of colorectal cancers is 66; for women, the median age is 69.
In the U.S., the highest rates of colon cancer are found in people who identify as Black, American Indian, or Alaska Native.
However, anyone can develop colon cancer. Well-known people who survived colon cancer include music manager and former talk-show host Sharon Osbourne, the Queen Mother, and at age 33, pro race car driver Scott Lagasse. Sadly, actor Chadwick Boseman passed away from colon cancer at age 43.
Hereditary syndromes result from gene mutations that are passed down through a biological parent. Ten percent of people diagnosed with colon cancer have an inherited gene mutation that puts them at high or moderately high risk. There are many hereditary syndromes that cause colon cancer, of which the most common are:
- Lynch syndrome.
Lynch syndrome is responsible for 3% of cases of colon cancer, but 8% of cases in people under age 50.
People with Lynch syndrome have the same risk of developing polyps as non-affected people. However, the polyps of people with Lynch syndrome are more likely to become cancerous.
People with Lynch syndrome have an increased risk of developing several other types of cancers, including cancers of the small intestine, bladder, stomach, ovary, and female breast.
- Familial Adenomatous Polyposis (FAP).
FAP is responsible for 1% of cases of colon cancer. A person with FAP can develop hundreds or even thousands of polyps by the time they are in their 20s. Since the likelihood of developing cancer is extremely high, most people with FAP have surgery to remove the colon.
- BRCA -1
The BRCA-1 mutation, commonly known as the mutation responsible for breast cancer in several ethnic groups, increases the risk of developing colon cancer by 50% when compared to people without the BRCA-1 mutation.
- MUTYH Associated Polyposis (MAP)
People with MAP, a rare syndrome, have multiple polyps and a 70 -75% risk of developing colon cancer.
Family history of colorectal polyps or colon cancer.
Having a family history of a disease does not necessarily mean that you have a genetically inherited syndrome that puts you at high risk. However, you do share some of the same genetic, ethnic, or racial background and you might have been raised with similar lifestyles and risk factors that can increase your risk of developing colon cancer. Your health care practitioner might recommend earlier screening if your family history includes (among many variations):
- one or more first degree relatives (parent, sibling, or child) with a diagnosis of colon cancer or a type of polyp called an adenoma
- one or more first or second-degree relatives with a diagnosis of colon cancer.
- One or more first or second-degree relatives with a diagnosis of colon cancer before age 55.
Obesity is a risk factor for colon cancer. More research is needed to separate out factors related to obesity, such as fat distribution.
Inflammatory bowel disease (Crohn disease or ulcerative colitis).
People with inflammatory bowel disease are at twice the risk for colon cancer compared with the general population.
Abdominal radiation in childhood or treatment with chemotherapy.
Type 2 diabetes.
Type 2 diabetes is associated with a slight increase in risk for colon cancer, independent of factors such as obesity that contribute to the development of diabetes.
Processed, smoked, fermented, or cured meats are associated with a slight increase in risk when eaten multiple times per week.
Studies have been mixed on the contribution of red meat to the risk of colon cancer. Meat cooked at lower temperatures may be preferable to charred meats.
There is a clear association between moderate to heavy drinking, defined as 2 to 4 or more drinks per day, and an increased risk of colon cancer.
Smoking, even if only in the past, is associated with increased risk.
How can I protect myself from developing colon cancer?
- Minimize your risk factors as much as possible.
- Get screened! Because of the recognition that colon cancer is increasingly found in younger people, some medical associations recommend that screening for people at average risk begin at age 45.
If you are opposed to having a colonoscopy, other screening methods are available.
- Make sure that your health care provider has documented not only your medical history, but also your family members medical histories. Be sure to update the history as you learn of any new diagnoses.
- Eat a balanced diet.
People who eat well balanced meals are highly likely to take in the nutrients needed to have a protective effect against colon cancer.
A healthy gut microbiome may have a protective effect against colon cancer. Read more.
- Get regular physical activity. People who get the most physical activity have a 25% lower risk of developing colon cancer than people who get the least. Most major medical associations recommend that people get 150 to 300 minutes of moderate-intensity activity, or 75 to 150 minutes of high-intensity activity a week. Find an exercise routine that you enjoy. Walk with a friend, find an exercise class at a gym or community center, or put on the radio and boogie to your favorites.
Check with your doctor and start slowly and carefully. It’s ok if you can’t do 150 minutes right away. Be proud of yourself for starting!
Science has come a long way in understanding the interplay of genetics, lifestyle, family history, and the environment on an individual’s risk of colon cancer. Ask your family members about their medical histories before your next exam. Tell your doctor about your risk factors and your family’s medical history, even if you don’t think any of it is relevant to colon cancer. Ask about genetic testing. And know that you are not too young or too healthy to develop colon cancer.
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