One of the risk factors for colon cancer is a family history of the disease. Having family members with colon cancer puts an individual at higher risk for developing colon cancer. Most colon cancers occur independently, but an estimated 5 to 10 percent of colon cancers are a direct result of heredity. Therefore, a person who has a family history of colon cancer and eventually develops the disease is more likely to have inherited the cancer gene than a person with no family history of colorectal cancer.
Check out our family history infographic at the bottom of this page
When a disease is said to be inherited, it means that it is passed down in the genetic code from one or both parents. A gene is a block of DNA that holds the instructions for making essential proteins for body functions. Abnormalities in the genetic code are known as a mutations which can result in disease. Mutations can occur many ways. They can:
Know Your Family’s History
Knowing your family’s health history is important because certain risk factors such as family history makes you a candidate for early screening. Although individuals at average risk for colon cancer should schedule their first colonoscopy around the age of 50, individuals who are at higher risk need to have a baseline screening earlier. If you have a family history of colon cancer, your doctor will help you to know when you should have your first colonoscopy.
The two most common inherited colorectal syndromes are hereditary nonpolyposis colorectal cancer (commonly known as Lynch Syndrome) and familial adenomatous polyposis (FAP). They affect both genders and can develop at very young ages. The children of men and women who carry the genetic code for HNPCC and FAP have a 50 percent chance of inheriting the disease-causing gene.
The more common type of inherited colon cancer is called hereditary nonpolyposis colorectal cancer (HNPCC) or Lynch Syndrome. Lynch Syndrome accounts for roughly 3 to 5 percent of all colon cancer diagnoses and usually affects family members in two or more generations. Families with a history of Lynch Syndrome usually have more family members develop colon cancer than typically expected. While the average age for a new diagnosis of colorectal cancer in the general population is 72, the average age of new diagnosis for someone with Lynch syndrome is only 45 years of age.
Individuals who have Lynch Syndrome are more prone to developing other cancers including endometrial (uterine), stomach, breast, ovarian, small bowel (intestinal), pancreatic, prostate, urinary tract, liver, kidney and bile duct cancers.
The classic diagnostic criteria for Lynch Syndrome are:
Screening options for Lynch syndrome include
Familial Adenomatous Polyposis
Another rare, but serious, genetic colon disease is Familial Adenomatous Polyposis or FAP. People affected by this genetic condition develop hundreds or thousands of precancerous polyps in the colon, and the number of polyps increases with age. Unless the colon is removed, polyps begin forming in the mid-teens and people with FAP will develop colon cancer in their thirties.
The average age that a person affected by classic FAP will develop colon cancer is 39 years of age. Some individuals have a variant of the disease and polyp growth is delayed. The average age of colon cancer onset is 55 years of age in this group.
Some facts about FAP:
If colon cancer runs in your family, please seek counsel from your doctor. Being in good communication with your doctor will help you know your risk and have a colon screening at the appropriate time. When it comes to genetic screening, there are benefits as well as risks. The good news is that a positive diagnosis will mean early treatment. However, genetic screening is costly, emotionally draining and can even be detrimental to an individual’s quality of life. You want to make the best choice for yourself and your family, so schedule regular visits with your doctor so you can have the best possible care.
Have a conversation with your family members about their colonoscopy history and results.
If you have a first-degree relative (parents, siblings or children) who had pre-cancerous polyps, you have a 35% to 70% higher chance of developing colon cancer.
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