Most people who develop colorectal cancer don’t have a family history. But as many as 1 in 3 people have other family members diagnosed with this type of cancer.
The American Cancer Society estimates
Cancer develops when gene mutations inside your cells cause them to replicate uncontrollably. Doctors usually don’t know why colorectal cancer develops, but a combination of your inherited genes and genetic mutations you acquire are both thought to play a role.
Most people who develop colorectal cancer don’t have a family history, but as many as
Read on to learn more about what’s known about the genetics of colorectal cancer.
Researchers estimate between
Colorectal cancer rates vary between ethnicities, likely at least partially due to inherited genes. People of
Most people who have colorectal cancer don’t have a family history.
However, having relatives who had colorectal cancer seems to increase your risk too.
The risk seems to be highest if you have a first degree relative who had cancer when they were younger than
In a
Familial cancer syndromes
About
A familial cancer syndrome is a predisposed risk of developing certain cancers due to genetic mutations passed through families. They often cause clusters of the same types of cancer among family members.
Syndromes associated with colorectal cancer include:
| Syndrome | Lifetime risk of colorectal cancer |
|---|---|
| Lynch syndrome | up to |
| familial adenomatous polyposis | nearly |
| Peutz-Jeghers syndrome | about |
| MUTYH-associated polyposis |
What is HNPCC (Lynch syndrome)?
Lynch syndrome, also called hereditary non-polyposis colorectal cancer (HNPCC), makes up about
- MLH1
- MSH2
- MSH6
Most people with gene mutations linked to Lynch syndrome will develop colorectal cancer. People with a uterus also have about a
Differences between familial adenomatous polyposis and colorectal cancer?
Familial adenomatous polyposis causes about
Almost everybody with familial adenomatous polyposis will develop cancer by age 40 if their colon isn’t removed.
People with familial adenomatous polyposis also have an increased risk of other cancers, including:
The U.S. Preventive Services Task Force very strongly recommends colorectal cancer screening for adults ages 50 to 75. The task force also strongly recommends screening for people ages 45 to 49.
Doctors use
- Fecal occult blood tests are stool tests that check for small amounts of blood.
- DNA stool tests look for DNA changes in your cells.
- Sigmoidoscopy is an examination of your lower colon using a tube with a camera.
- Colonoscopy is an examination of your entire colon with a tube with a camera.
- CT colonography is an examination of your colon with CT imaging.
If you have an increased risk of colorectal cancer, it’s a good idea to talk with your doctor about which type of screening is best for you.
If you’re between the ages of 76 and 85, it’s a good idea to have a conversation with your doctor to learn whether you may benefit from colorectal cancer screening.
Researchers have identified many gene mutations associated with the development of colorectal cancer. Knowing which mutations you have helps doctors determine how to best treat your cancer.
The
| Gene | Prevalence |
|---|---|
| APC | 80%–82% |
| TP53 | 48%–59% |
| KRAS | 40%–50% |
| PIK3CA | 14%–18% |
Other
- obesity
- low fiber and high fat diet
- diet high in processed meats
- diet low in fruits and vegetables
- lack of physical activity
- smoking or tobacco use
- high alcohol consumption
- inflammatory bowel disease (IBD)
Genetic testing may be beneficial if you have a family history of colorectal cancer, especially if you have a parent or sibling with colorectal cancer.
Genetic testing can be performed with a sample of your:
- blood
- polyp
- tumor
For people who haven’t yet received a diagnosis of Lynch syndrome, doctors often recommend testing if you meet the
- You have at least three relatives with cancer linked to Lynch syndrome.
- One relative is a first degree relative.
- At least two generations in your family are affected.
- At least one relative had cancer before age 50.
It’s important to get tested as soon as possible if you have a family history of familial adenomatous polyposis. The
Most people who develop colorectal cancer don’t have a family history, but having a first degree family member with colorectal cancer increases your risk of developing it, too.
A small percentage of people with colorectal cancer have familial cancer syndromes. These syndromes often cause clusters of colorectal cancer within a family.