ABC Medical Center > Cancer > What is colorectal cancer?

What is colorectal cancer?

20 February 2018


The term colorectal cancer is used to refer to cancer that starts in the colon or rectum, depending on its origin, and they are often grouped together because they have many common features.

Risk factors for colorectal cancer

Many lifestyle factors have been linked to colorectal cancer. In fact, there is a strong relationship between diet, weight, and exercise with the risk of colorectal cancer.

Some modifiable factors are:

Overweight or obesity

Being overweight or obese increases the risk of colorectal cancer. Being overweight increases the risk of colon cancer in both men and women, although this association is stronger among men.

Physical inactivity

A sedentary lifestyle leads to a higher probability of developing colorectal cancer. Being active could help lower your risk.

Certain types of food

A diet high in red meat (beef, pork, lamb, or liver) and processed meats (such as hot dogs and cold cuts) increases the risk of colorectal cancer.

Cooking meats at very high temperatures (frying, roasting, or grilling) creates chemicals that can increase cancer risk, although it’s not clear by how much this may increase your risk.

A diet high in vegetables, fruits, and whole grains have been linked to a lower risk of colorectal cancer, although fiber supplements have not been shown to help reduce this risk.


People who have smoked for a long time are more likely to get it than people who haven’t. Smoking is known to cause lung cancer, but it is also linked to other cancers, such as colorectal cancer.

Excessive alcohol consumption

Limiting alcohol consumption to no more than two drinks a day for men and one drink a day for women could have many health benefits, including a lower risk of colorectal cancer.

Non-modifiable factors:

Old age

The risk of colorectal cancer increases with age. Younger adults can get colorectal cancer, but the chances increase significantly after age 50.

Personal history of colorectal cancer or colorectal polyps

If there is a history of adenomatous polyps (adenomas) in the colon or rectum, there is an increased risk of colorectal cancer. This is especially true if the polyps are large or if there are many of them.

If you have had colorectal cancer, even if it was completely removed, you are more likely to get new cancers in other areas of the colon and rectum. The chances of this happening are higher if you developed colorectal cancer at a younger age.

Personal history of inflammatory bowel disease

Having inflammatory bowel disease (IBD), including ulcerative colitis or Crohn’s disease, increases the risk of colorectal cancer.

IBD is a condition in which the colon is inflamed for a very long time. People who have had IBD for many years often develop dysplasia. The term dysplasia is used to describe cells in the lining of the colon or rectum that look abnormal (but are not cancerous) but can turn into cancer over time.

People with IBD should start colorectal cancer screening at a younger age and be screened more often.

Inflammatory bowel disease is different from irritable bowel syndrome (IBS). IBS is not related to colorectal cancer.

Family history of colorectal cancer or adenomatous polyps

Most colorectal cancers are found in people with no family history. Despite this, one in five people with colorectal cancer have other relatives who have had it

People with a history of colorectal cancer in a first-degree relative (parents, siblings, or children) have a higher risk. The risk is even higher if the first-degree relative was diagnosed when under 45 years of age or affected by more than one first-degree relative.

The causes of the increased risk are not clear in all cases. Cancers that “run in families” may be due to inherited genes, shared environmental factors, or some combination of factors.

Having relatives who have had adenomatous polyps is also linked to an increased risk of colon cancer.

Hereditary syndromes

About 5% to 10% of people with colorectal cancer have inherited genetic defects (mutations) that can cause familial cancer syndromes and can lead to the disease.

The most common inherited syndromes associated with colorectal cancers are familial adenomatous polyposis and Lynch syndrome (hereditary non-polyposis colorectal cancer or HNPCC), although other less common syndromes can also increase the risk for colorectal cancer.

Ethnic and racial background

Black people have the highest colorectal cancer incidence and death rates of any racial group in the United States. Such reasons are still unknown.

Eastern European Jews (Ashkenazi Jews) have one of the highest risks of colorectal cancer compared to any other ethnic group in the world. Several genetic mutations have been found that increase the risk of colorectal cancer in this group. The most common of these genetic changes, called the I1307K APC mutation, occurs in about 6% of Jews in the United States.

Type 2 diabetes

People with type 2 diabetes have an increased risk of colorectal cancer. Both type 2 diabetes and colorectal cancer share some of the same risk factors. However, even when these factors are considered, people with type 2 diabetes are still at increased risk. These people also often have a less favorable prognosis after diagnosis.

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