Multiple risk factors that may raise an individual’s risk of colorectal cancer or polyps have been identified by researchers.
What is a risk factor?
Anything that increases your likelihood of contracting a disease like cancer is considered a risk factor.
There are various risk factors for various malignancies. Certain risk factors are modifiable, such as smoking. Some are unchangeable, such as an individual’s age or family history of cancer.
However, having one or more risk factors does not guarantee that you will develop the illness. Furthermore, some disease-stricken individuals might not have any recognized risk factors.
Risk factors you can change
Colorectal cancer has been connected to numerous lifestyle variables. In actuality, modifiable risk factors are associated with over half of all colorectal cancer cases.
Being overweight or obese
You have an increased risk of acquiring and passing away from colorectal cancer if you are fat or extremely overweight. People who are overweight have a higher risk of colorectal cancer; however, the association appears to be stronger in men. Achieving and maintaining a healthy weight may reduce your risk.
Diabetes mellitus, Type 2
Individuals who have type 2 diabetes mellitus have a higher risk of colorectal cancer than those who do not. Researchers hypothesize that persons with diabetes mellitus may have elevated insulin levels, which would explain this increased risk. Some of the risk factors for type 2 diabetes and colorectal cancer are similar (e.g., being overweight and physically inactive). However, the risk remains elevated for those with type 2 diabetes even after accounting for these variables. Additionally, after diagnosis, their prognosis (outlook) is typically less good.
Certain types of diets
A diet heavy in processed meats (such hot dogs and various lunch meats) and red meats (like liver, pig, lamb, or beef) increases your risk of colorectal cancer over time.
When you fry, broil, or grill meat at extremely high temperatures, chemicals are produced that may increase your risk of cancer.
Having a low blood level of vitamin D may also increase your risk.
It is likely less risky to follow a healthy eating pattern that consists of lots of fruits, vegetables, whole grains, and little to no red and processed meats as well as sugar-filled beverages.
Smoking
Long-term tobacco users have an increased risk of colon cancer and death from the disease compared to non-smokers. Additionally, colon polyps are more common in persons who smoke. In addition to being a well-known cause of lung cancer, smoking is also associated with a number of other malignancies. See How to Quit Using Tobacco if you smoke and would like additional information about stopping.
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. It is best not to drink alcohol. If people do drink alcohol, they should have no more than 2 drinks a day for men and 1 drink a day for women. This could have many health benefits, including a lower risk of many kinds of cancer.
Colorectal cancer risk factors you cannot change
Your age
Your risk of colorectal cancer goes up as you age. Younger adults can get it, but it’s much more common after age 50. Colorectal cancer is rising among people who are younger than age 50, and the reason for this remains unclear.
Your racial and ethnic background
American Indian and Alaska Native people have the highest rates of colorectal cancer in the United States, followed by African American men and women.
Jews of Eastern European descent (Ashkenazi Jews) have one of the highest colorectal cancer risks of any ethnic group in the world.
Your sex at birth
Men who have colorectal cancer are more likely to die from it than women. The reasons are not fully clear. Women who have colorectal cancer are more likely to have right-sided colon cancer, particularly if they are no longer menstruating (postmenopausal).
Cholecystectomy
People who have had their gallbladder removed (cholecystectomy) have been found to have a mildly higher risk for right-sided colon cancer. It’s not fully understood why this is. Research is ongoing.
A personal history of colorectal polyps or colorectal cancer
If you have a history of adenomatous polyps (adenomas), you are at increased risk of developing colorectal cancer. This is especially true if the polyps are large, if there are many of them, or if any of them show dysplasia.
If you’ve had colorectal cancer, even though it was completely removed, you are more likely to develop new cancers in other parts of the colon and rectum. The chances of this happening are greater if you had your first colorectal cancer when you were younger.
A personal history of inflammatory bowel disease
If you have inflammatory bowel disease (IBD), including either ulcerative colitis or Crohn’s disease, your risk of colorectal cancer is increased.
IBD is a condition in which the colon is inflamed over a long period of time. People who have had IBD for many years, especially if untreated, often develop dysplasia. Dysplasia is a term used to describe cells in the lining of the colon or rectum that look abnormal, but are not cancer cells. They can change into cancer over time.
If you have IBD, you may need to start getting screened for colorectal cancer when you are younger and be screened more often.
Inflammatory bowel disease is different from irritable bowel syndrome (IBS), which does not appear to increase your risk for colorectal cancer.
A personal history of radiation to the abdomen or pelvis area
If you survived cancer in the past and as part of your treatment, received radiation to the area where your colon is (abdomen and pelvis area), your risk of colorectal cancer is increased. If you have received radiation to the abdomen or pelvis, especially as a child, you may need to start getting screened for colorectal cancer when you are younger and be screened more often.
Several studies suggest that men who had radiation therapy to treat prostate cancer might have a higher risk of rectal cancer because the rectum receives some radiation during treatment. Most of these studies are based on men treated in the 1980s and 1990s, when radiation treatments were less precise than they are today. The effect of more modern radiation methods on rectal cancer risk is not clear, but research continues to be done in this area.
A family history of colorectal cancer or adenomatous polyps
Most colorectal cancers are found in people without a family history of colorectal cancer. Still, as many as 1 in 3 people who develop colorectal cancer have other family members who have had it.
People with a history of colorectal cancer in a first-degree relative (parent, sibling, or child) are at increased risk. The risk is even higher if that relative was diagnosed with cancer when they were younger than age 50, or if more than one first-degree relative is affected.
The reasons for the increased risk are not clear in all cases. Cancers can “run in the family” because of inherited genes, shared environmental factors, or some combination of these.
Having family members who have had adenomatous polyps is also linked to a higher risk of colon cancer. (Adenomatous polyps are the kind of polyps that can become cancer.)
If you have a family history of adenomatous polyps or colorectal cancer, talk with your doctor about the possible need to start screening at a younger age. If you’ve had adenomatous polyps or colorectal cancer, it’s important to tell your close relatives so that they can pass along that information to their doctors and start screening at the right age.
Having an inherited syndrome
About 5% of people who develop colorectal cancer have inherited gene changes (mutations) that cause family cancer syndromes and can lead to them getting the disease.
The most common inherited syndromes linked with colorectal cancers are Lynch syndrome (hereditary non-polyposis colorectal cancer, or HNPCC) and familial adenomatous polyposis (FAP), but other rarer syndromes can increase colorectal cancer risk, too.
Lynch syndrome (hereditary non-polyposis colon cancer or HNPCC)
The most prevalent hereditary colorectal cancer syndrome is Lynch syndrome. It makes up between 2% and 4% of all colorectal cancer cases. In most cases, this disorder is caused by an inherited defect in either the MLH1, MSH2,MSH6, PMS2, or EPCAM gene, but changes in other genes can also cause Lynch syndrome. These genes are known as DNA mismatch repair (MMR) genes, and they often aid in the repair of damaged DNA.The malignancies associated with this syndrome typically strike relatively young individuals and are more likely to be right-sided colon tumors. Although polyps are possible in people with Lynch syndrome, they usually have few of them. Depending on which gene is impacted, a person with this syndrome may have a 50% lifetime risk of developing colorectal cancer.
Women who have this illness are also at a high risk of endometrial cancer, which is cancer of the lining of the uterus. Cancers of the ovary, stomach, small intestine, pancreas, kidney, prostate, breast, ureters (tubes that transfer urine from the kidneys to the bladder), and bile duct are among the other cancers associated with Lynch syndrome. Individuals with Turcot syndrome, an uncommon hereditary disorder, who possess a mutation in one of the Lynch syndrome genes are more vulnerable to colon cancer and glioblastoma, a particular kind of brain cancer.
For more on Lynch syndrome, see What Causes Colorectal Cancer?, Can Colorectal Cancer Be Prevented?, and Family Cancer Syndromes.
Familial adenomatous polyposis (FAP)
FAP is caused by changes (mutations) in the APC gene that a person inherits from their parents. About 1% of all colorectal cancers are caused by FAP.
In the most prevalent kind of FAP, a person’s colon and rectum may produce hundreds or thousands of polyps; this commonly begins in the age range of 10 to 12. One or more of these polyps typically develop cancer as early as age 20. If their colon hasn’t been removed to prevent it, nearly all FAP patients will have colon cancer by the time they are 40. Additionally, tumors of the stomach, small intestines, pancreas, liver, and a few other organs are more common in people with FAP.
There are 3 sub-types of FAP:
Patients with attenuated FAP or AFAP typically have fewer polyps (less than 100) and develop colorectal cancer later in life (in their 40s and 50s).
In addition to causing noncancerous tumors of the skin, soft tissues, and bones, Gardner syndrome is a kind of FAP.
Individuals with Turcot syndrome who carry an APC gene mutation are highly susceptible to developing multiple adenomatous polyps, colon cancer, and medulloblastoma, a particular kind of brain cancer.
Rare inherited conditions linked to colorectal cancer
Peutz-Jeghers syndrome (PJS): Individuals with this hereditary disorder typically have hamartomas, a particular kind of polyp, in their digestive tract and freckles around their mouths (and occasionally on their hands and feet). These individuals have a significantly increased risk of developing colorectal cancer in addition to other cancers like pancreatic, ovarian, and breast cancer. Typically, they receive a diagnosis earlier than typical. The STK11 (LKB1) gene mutations that cause this condition.
Individuals suffering from MUTYH-associated polyposis (MAP) experience an abundance of colon polyps. If they are not regularly monitored with colonoscopies, they often develop into cancer. These individuals are also more susceptible to malignancies of the breast, ovaries, thyroid, bladder, and gastrointestinal tract. This disease, which frequently results in cancer at an earlier age, is brought on by mutations in the MUTYH gene, which is involved in “proofreading” the DNA and correcting any errors.
The genetic disorder known as cystic fibrosis (CF) causes cells in specific body organs to produce mucus that is stickier and thicker than usual. Health issues may result from this, particularly in the pancreas and lungs. Better medical care has extended the life expectancy of persons with cystic fibrosis (CF), but it has also shown that CF patients are more susceptible to colorectal cancer, which typically strikes considerably earlier than in the case of healthy individuals. An organ transplant recipient, such as someone who received a lung transplant, is considerably more at risk for colorectal cancer. The CFTR gene is mutated, and this results in CF.
Finding families with these inherited disorders is crucial because many of them are connected to colorectal cancer at an early age as well as other cancer types. It enables medical professionals to suggest particular actions, including screening and other preventive measures, when the patient is younger. Genetic Testing, Screening, and Prevention for People with a Strong Family History of Colorectal Cancer provides information on risk assessment, genetic counseling, and testing for several of these diseases.