Most lung cancer is not inherited, but some people carry genes that raise their risk
About 8 to 10 percent of people diagnosed with lung cancer have a family history of the disease. That does not mean they inherited it directly. Most lung cancer develops because of smoking, secondhand smoke, radon exposure, or occupational hazards — things that happen to your lungs over time, not things written in your DNA.
However, some families do carry genetic mutations that make lung cancer more likely. These are rare. The most studied ones are mutations in the EGFR gene, the ALK gene, and the KRAS gene. If you have one of these mutations, your cells are more prone to becoming cancerous. But having the mutation does not mean you will get lung cancer — it means your risk is higher than average.
The difference matters because it changes how doctors treat you if you do develop the disease, and it may change screening decisions for your relatives. It does not change whether you should quit smoking or avoid radon.
Key Takeaways
- Most lung cancer is caused by exposure to smoke, radon, or workplace hazards, not by inherited genes.
- Some families carry genetic mutations like EGFR, ALK, or KRAS that raise lung cancer risk, but these are uncommon.
- Having a family history of lung cancer does not automatically mean you carry a genetic mutation.
- Genetic testing is usually done after a lung cancer diagnosis to guide treatment, not before diagnosis to predict risk.
- If a close relative had lung cancer, talking to a genetic counselor can help you understand your actual risk and what screening makes sense.
What genetic mutations actually do in lung cancer
A genetic mutation is a change in the DNA instructions that tell your cells how to grow and divide. Some mutations make cells more likely to become cancerous. In lung cancer, the most common inherited mutations are in genes that normally act as brakes on cell growth.
The EGFR mutation is found in about 10 to 15 percent of lung cancers in the United States, and more often in people of East Asian descent and in people who have never smoked. The ALK mutation appears in about 3 to 5 percent of lung cancers, usually in younger people. The KRAS mutation is found in about 30 percent of lung cancers and is more common in people with a smoking history.
If you have one of these mutations and develop lung cancer, your doctor can prescribe targeted drugs that work specifically against that mutation. That is why genetic testing after diagnosis matters — it changes your treatment options. But these mutations are not the same as inheriting a predisposition. You can have the mutation and never develop cancer. You can also develop lung cancer without having any of these mutations.
The difference between inherited risk and acquired mutations
An inherited mutation is one you are born with, passed down from a parent. You carry it in every cell of your body. An acquired mutation is one that develops in a single cell or group of cells over time, usually because of exposure to something harmful like cigarette smoke or radon.
Most lung cancer mutations are acquired, not inherited. A cell in your lung gets damaged by smoke or radiation, the damage accumulates over years, and eventually that cell becomes cancerous. This is why lung cancer risk goes up with age and with years of exposure.
Inherited mutations are rarer. If you have an inherited EGFR, ALK, or KRAS mutation, you were born with it. But even then, you might never develop lung cancer — the mutation raises your risk, but it does not may provide disease. You would also need additional exposures or additional mutations in that cell to push it toward cancer.
When family history matters and when it does not
If multiple people in your family have had lung cancer, especially if they were young or never smoked, that pattern suggests a possible inherited mutation. If your parent, sibling, or child had lung cancer before age 50, or if three or more relatives across generations had it, a genetic counselor can help you figure out whether testing makes sense.
If only one relative had lung cancer and they were a smoker, or if they were older when diagnosed, family history is less likely to point to an inherited mutation. It might just mean your family shares a risk factor — like living in a house with radon, or working in construction.
Genetic counselors are trained to look at your family tree and tell you whether the pattern suggests inherited risk. They can be found through your primary care doctor, through a cancer center, or through the National Society of Genetic Counselors website. Many insurance plans cover genetic counseling even before you have been diagnosed with cancer.
Genetic testing: when it happens and what it shows
Genetic testing for lung cancer usually happens after you have been diagnosed, not before. If you are diagnosed with lung cancer, your doctor will order tests on the tumor itself to look for EGFR, ALK, KRAS, and other mutations. This tells your doctor which drugs might work best for you.
Testing before diagnosis — when you have no symptoms and no cancer — is less common and usually only recommended if you have a strong family history and you are considering screening with CT scans. Some people with a family history of lung cancer and heavy smoking histories do get annual low-dose CT screening, and genetic information might help your doctor decide whether that is right for you.
If you want genetic testing because of family history, ask your doctor for a referral to a genetic counselor. They will review your family history, explain what testing can and cannot tell you, and help you decide whether it makes sense. Testing usually involves a blood sample or saliva sample and takes a few weeks to get results.
What to do if lung cancer runs in your family
If a close relative had lung cancer, the most important step is to reduce your own exposure to known risk factors. Do not smoke. Test your home for radon — you can buy a radon test kit at a hardware store for under $30, or hire a professional to test. If you work in construction, mining, or another industry with air hazards, use protective equipment and follow safety rules.
Talk to your doctor about your family history. If the pattern suggests inherited risk, ask for a referral to a genetic counselor. If you have a heavy smoking history and a family history of lung cancer, ask whether annual CT screening is right for you — this is a conversation, not a decision your doctor makes alone.
You do not need to wait for a genetic test to take these steps. Reducing exposure helps whether or not you carry a genetic mutation. And if you do carry a mutation, you still benefit most from not smoking and avoiding radon.
Frequently Asked Questions
If my parent had lung cancer, will I definitely get it?
No. Even if your parent had lung cancer caused by an inherited mutation, you might not develop the disease. Having the mutation raises your risk, but many people with mutations never get cancer. Your actual risk depends on the specific mutation, your exposures, and other factors a genetic counselor can help explain.
Can I get genetic testing if I have never been diagnosed with cancer?
Yes, but it is usually recommended only if you have a strong family history of lung cancer, especially if relatives were young when diagnosed or never smoked. A genetic counselor can review your family history and tell you whether testing makes sense for you. Your doctor can refer you to one.
What does it mean if I have an EGFR mutation but no lung cancer?
It means your cells carry a change that makes them more prone to becoming cancerous, but you have not developed cancer yet. You should avoid smoking and radon exposure. Talk to your doctor about whether screening with CT scans is right for you, especially if you have other risk factors.
If my sibling had lung cancer, should I get screened?
That depends on your age, smoking history, and whether your sibling's cancer suggests an inherited mutation. A doctor or genetic counselor can review your situation and tell you whether screening is recommended. Generally, screening is offered to people over 50 with a significant smoking history, but family history may change that recommendation.
Does having a family history of lung cancer mean I should never smoke?
Yes. If lung cancer runs in your family, smoking raises your risk far more than it does for someone without family history. The combination of inherited risk and smoking exposure is much more dangerous than either one alone. Not smoking is the single most important thing you can do.