This information explains how having the I1307K mutation in the APC gene may affect you and your family.
In this resource, the word “family” means family members related to you by blood. They are not related to you through marriage or adoption.
Your APC gene normally helps prevent cancers. A mutation in this gene causes it to stop working like it should. This increases your risk for certain types of cancers.
I1307K is the name of a specific mutation in the APC gene that prevents it from working like it should.
What is my cancer risk if I have the APC I1307K mutation?
The APC I1307K mutation slightly increases your risk of getting polyps (growths of tissue) in your colon and rectum. These polyps can lead to an increased risk for colorectal (colon and rectal) cancer.
The APC I1307K mutation is different from other mutations in the APC gene. Most mutations in the APC gene are rare and cause a serious condition called Familial Adenomatous Polyposis (FAP). The APC I1307K mutation doesn’t cause FAP or increase the risk for polyps or cancer as much as other APC gene mutations.
The APC I1307K mutation is common. Around 6% to 10% of people with Ashkenazi (Eastern European) Jewish ancestry have this mutation. People of non-Jewish ancestry can also have this mutation.
As we learn more about these mutations, we may learn they increase the risk for other types of cancers. Your genetic counselor will give you more information about your cancer risk if you have a mutation.
For more information, read Frequently Asked Questions About Hereditary Cancers.
What can I do about my cancer risk if I have the APC I1307K mutation?
If you have the I1307K mutation, your genetic counselor will review your results and your personal and family history of cancer and give you recommendations.
They may recommend you start having cancer screenings at a younger age, have them more often than most people, or get specialized screenings to help find cancer as early as possible.
Some examples of these cancer screenings include having colonoscopies starting at an earlier age and more often than most people.
Your genetic counselor will also talk with you about whether there are any other screening or prevention options that may be right for you.
What happens if I don’t have the APC I1307K mutation?
If you don’t have the I1307K mutation, your genetic counselor will review your personal and family history and talk with you about the general cancer screening guidelines you should follow.
What does the APC I1307K mutation mean for my blood relatives?
If you have a mutation, your biological parents, siblings, and children each have a 50% chance of having the same mutation. This means there’s an equal chance they will or won’t have the mutation. Your distant family members may also be at risk for having the same mutation.
Males and females have an equal chance of passing down a mutation in their family. You only need to inherit a mutation from one parent to have an increased risk for cancer.
Your genetic counselor will review your family history and talk with you about whether they recommend genetic testing for your blood relatives.