It’s easy and natural to assume that if you have a family history of something, then that something may be genetic. I think this is especially the case when it comes to cancer, as nearly everything we hear in the media and in our culture hammers home the idea that if you have a family history of cancer, you are at an increased risk for it. This is certainly true, but there are many reasons a family history can lead to an increased risk, and genetic or hereditary susceptibility is just one of those and is actually one of the more rare reasons. Nearly every patient I ever saw in clinic was surprised when I told them that only about 10% of all cancers are hereditary.
Since hereditary cancer is so rare, it does not make sense to test everyone’s genes to see if they have a change, or mutation, which leads to increased risk. Rather, what genetic counselors and other medical professionals do is look for clues in the family history which suggest a genetic mutation might be present, and therefore identify good candidates for genetic testing. Some of those clues include:
- Early age at cancer diagnosis: Usually any diagnosis before age 50 is considered “early.” When a genetic mutation is inherited from a parent, it is present in a person’s cells even before they are born, and since hereditary mutationsmake it easier for a person to develop cancer, cancers are more likely to develop before they typically would.
- Diagnosis of rare cancer(s): When a rare cancer develops, there is often the question of why. A hereditary mutation could be a possible explanation, especially if there is a family history of other rare cancers.
- Diagnosis of multiple primary cancers: If a person has a hereditary mutation, and is therefore more likely to develop cancer in general, he or she is also more likely to develop cancer more than once. Just to be clear here, I’m talking about two or more new cancers. A recurrence of an “old” cancer is not the same, as that reflects the original treatment was not working 100%.
- Diagnosis of multiple same or related cancers in the family: If multiple people in the family have been diagnosed with the same type, or related types of cancer, one possible explanation is a hereditary mutation may be present in the family. It’s not always obvious which cancers are related to each other, so if you have different types of cancer in your family, you may wish to consult with a genetic counselor or other medical professional for further discussion.
Having one or more of these clues present in your personal or family history does not absolutely mean you or your family has a hereditary mutation for cancer susceptibility. However, it does mean it’s a possibility, so it might be worth talking to your doctor about a referral for additional genetic assessment. You can also use the Hereditary Cancer Risk Indicator to see if you are at risk of having a hereditary mutation and learn more about next steps.
