You may know someone who has smoked cigarettes for decades and hasn’t developed lung cancer. You may also know someone who never smoked a single cigarette but who has been diagnosed with the disease. Smoking cigarettes puts you at the highest risk of developing lung cancer — around 80 percent of lung cancer deaths are linked to a history of smoking tobacco. However, only 10 percent to 20 percent of people with a history of smoking develop lung cancer. Cancer researchers aren’t sure yet why some people who smoke develop lung cancer while others don’t.

Read on to learn what’s known and what’s still being studied about why some people who smoke don’t get lung cancer.

How Does Lung Cancer Develop?

Lung cancer, like all cancers, develops when genetic mutations (changes) build up in the DNA of normal, healthy lung cells. For cancer to develop, the genetic mutations must encourage cells to divide and grow in an abnormal, disorganized way. These cell mutations are usually in genes related to cell growth or tumor suppression, which normally work to control cell growth and keep it orderly. DNA mutations can interfere with the role of these genes. This interference can cause cells to multiply and form a tumor, causing cancer.

Some chemicals can increase the rate of genetic mutation, especially over long periods of time. Chemicals that can increase the risk of cancer are known as carcinogens. Not all genetic mutations will lead to lung cancer. The longer cells live, the more time they have to accumulate mutations. Cells that line the lungs can live for years, or even decades. That’s why these cells are the most likely to become cancerous. The growing collection of mutations in lung cells increases the chance that a lung cancer-associated gene could become mutated.

1. DNA Repair May Prevent Lung Cancer in Some People Who Smoke

Smoking tobacco is the leading risk factor for lung cancer. Tobacco smoke contains at least 70 carcinogens (chemicals known to cause cancer). Use of tobacco products — whether cigarettes, cigars, vapes, or e-cigarettes — is thought to increase the risk of genetic mutation in lung cells. Recent research has confirmed that people who smoke cigarettes accumulate mutations in lung cells faster than those who have never smoked. This leads to a higher risk of lung cancer, but it doesn’t always result in lung cancer, even among people who smoke heavily.

Cells have biological tools that can repair and correct damaged DNA, thereby preventing mutations from building up over time. Recent research has found that even people who smoke heavily may be protected from developing lung cancer if they have genes with strong DNA-repair mechanisms. This may be one reason why some people who smoke frequently don’t develop lung cancer.

2. Risk for Lung Cancer Increases With Age

Young people who smoke are less likely to be diagnosed with lung cancer. As people age, they accumulate more and more genetic mutations. This can increase the risk of developing lung cancer. Most lung cancer diagnoses occur in people aged 65 and older. The average age of people diagnosed with lung cancer is 70. Only a small number of lung cancer diagnoses are made in people under age 45.

3. Family History of Lung Cancer May Increase Your Risk

Having a parent or sibling diagnosed with lung cancer may increase your risk of developing lung cancer. This familial risk could be caused by shared environmental risk factors, like exposure to secondhand smoke or other chemicals in the same household.

Only about 8 percent of lung cancer cases are directly caused by genes passed down from your parents. People who smoke and who have not inherited a genetic mutation that causes lung cancer are at a lower risk than people who smoke and who do have the mutation.

4. Avoiding Certain Chemicals May Lower Your Risk

Cancer-causing agents can be present in your workplace, home, or the environment around you. People who smoke heavily have less exposure to these cancer-causing agents might have a lower risk of developing lung cancer compared to people who smoke with a high exposure.

Here are a few of the chemicals known to raise the risk for lung cancer.

Radon

People who smoke and who have not had heavy exposure to radon may have a lower risk of lung cancer than those who haven’t been exposed to the gas.

Radon gas naturally occurs when uranium in rocks and soil breaks down. It has no odor or color. Breathing in radon can increase your risk of lung cancer. Radon exposure is the leading cause of lung cancer in people who do not smoke. Radon is found in some homes, basements, and other buildings in nearly every part of the United States.

Air Pollution

People who smoke heavily and live in rural areas with low levels of air pollution may have a lower risk of developing lung cancer than those who reside in urban areas and cities. Extended exposure to outdoor air pollution may be responsible for up to 5 percent of lung cancer deaths. This may especially be the case in cities with high levels of air pollution.

Asbestos

People who smoke who’ve never been exposed to asbestos may have a lower risk of lung cancer than people who have been exposed to the material.

Asbestos is a fibrous material used as insulation in homes and buildings. If inhaled, asbestos can permanently implant and irritate the lungs. Most lung cancer cases occur 15 years after the first asbestos exposure. The use of asbestos as insulation has been discontinued. However, asbestos remains installed in some homes, and it’s still used in some mills, mines, textile factories, and other workplaces. Long-term exposure to asbestos results in a greater risk of lung cancer.

Other Workplace Chemicals

Other carcinogens can be found in the workplace that increase the risk of lung cancer, including:

• Radioactive ores, such as uranium
• Diesel exhaust
• Inhaled chemicals such as mustard gas, chromium compounds, coal products, ethers, beryllium, cadmium, arsenic, silica, vinyl chloride, and nickel compounds

People who smoke but don’t work around these cancer-causing agents may have a lower risk of developing lung cancer compared with those who are often exposed.

Radiation Therapy

People who have received radiation therapy to the chest, such as for the treatment of breast cancer, have an increased risk of later developing lung cancer. Radiation therapy is a useful cancer treatment because it damages cancerous cells with high-energy particles or waves. This damage can slow or stop cancer cell growth or kill the cancerous cells. Radiation therapy can also damage healthy cells and increase the number of genetic mutations, potentially leading to cancer over time. People who smoke and who have not received radiation therapy may have a lower risk of developing lung cancer compared with those who were exposed to chest radiation.

How Can You Decrease Your Risk of Lung Cancer?

There is no certain way to avoid getting lung cancer, but you can decrease some of your risks. While you may not be able to avoid risks like previous radiation therapy, you can manage lifestyle and environmental factors to lower your risk, including:

• Monitoring radon levels and implementing methods to decrease high levels of radon
• Using protective equipment when working with asbestos
• Using protective equipment and following safety procedures when working with cancer-causing chemicals or radiation

Beta-Carotene and Antioxidant Supplements

Antioxidant supplements were once thought to reduce the risk of lung cancer, but study results have been inconsistent. A 2022 review of past research found that antioxidant supplements, such as vitamin E, vitamin C, copper, and zinc, as well as beta-carotene supplements, have shown varied effects on the risk of developing lung cancer among people who smoke. Some studies indicate a potential protective effect, while others suggest no benefit or even increased risk. The relationship between these supplements and lung cancer risk remains unclear, and more research is needed to determine whether dietary supplements can reliably reduce lung cancer risk in people who do and do not smoke.

Always check with your doctor before you start taking a new supplement.

Should You Stop Smoking After a Lung Cancer Diagnosis?

There are several good reasons to stop smoking after being diagnosed with lung cancer:

• People who stop smoking after a lung cancer diagnosis live longer than those who keep smoking.
• If you smoke and have been diagnosed with lung cancer, continuing to smoke could make your cancer progress faster.
• Stopping smoking might allow cancerous cells in your lungs to be replaced with healthy cells, even among people who smoke heavily or have smoked for a long time.

By staying informed and taking steps to avoid harmful chemicals, you can lower your risk of developing lung cancer. It’s important to talk to your doctor for advice on how to stay healthy and reduce your risk. They can provide guidance and support tailored to your needs. Talk to your doctor if you want to quit smoking but need support.

Connect With Others Who Understand

On MyLungCancerTeam, the social support network for people with lung cancer and their loved ones, more than 13,000 members come together to ask questions, give advice, and share their stories with others who understand.

Do you have risk factors for lung cancer apart from smoking? Share your insights in the comments below, or start a conversation by posting on your Activities page.