Is Lung Cancer Inherited?

If Someone in My Family Has Lung Cancer, Am I More Likely to Get It?

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Is lung cancer hereditary?. istockphoto.com

It is well known that some cancers, such as ovarian cancer and colon cancer, run in families. Even though the role of heredity in lung cancer is not as well-known, having a family history of lung cancer does increase the risk to some degree. Lung cancer is more likely to be related to a genetic predisposition in women, in nonsmokers and in lung cancer in young adults. Overall, it has been estimated that 1.7 percent of lung cancers up to the age of 68 are hereditary. Let's look at some of the ways that a family history of lung cancer can affect an individuals risk.

How Closely a Family Member is Related

Having a first-degree family member (parent, sibling or child) with lung cancer roughly doubles the risk of developing lung cancer. This risk is greater for women than men, and stronger in nonsmokers than smokers. Having a second-degree relative (an aunt, uncle, niece or nephew) with lung cancer increases risk by around 30 percent.

People Who Are More Likely to Have Hereditary Lung Cancer

There are some groups of people who are more likely to have a hereditary predisposition to lung cancer than others. The average age for lung cancer at the current time is 71. People who have lung cancer when they are younger than this suggest that genetics may be involved. Even if someone has smoked but is only 50, this is very true.

Men and women are about equally likely to develop cancer at the current time. Lung cancer in women, however, is more likely to have a genetic component. Women are also more likely to develop lung cancer at a young age.

In some regions of the world, familial lung cancer appears to be much more common than others. For example, in Xuanwei City in the Yannan Province of China, the incidence of hereditary lung cancer is very high.

Smoking Status, Lung Cancer, and Heredity

Smokers who develop lung cancer are less likely to have a family history than ​non-smokers who develop lung cancer. That said, however, for those who have a genetic predisposition to lung cancer, smoking appears to amplify that risk.

Type of Lung Cancer and Heredity

Studies vary in the types of lung cancers that have the greatest hereditary component, but those with nonsmall cell lung cancers, especially lung adenocarcinoma are more likely to have a family history of lung cancer than those with small cell lung cancers.

A recent finding is that non-smokers with non-small cell lung cancer whose tumors have an EGFR mutations are much more likely to have a family history of lung cancer than those who have an ALK rearrangement or KRAS mutation.

Breast Cancer Gene (BRCA2) and Risk of Lung Cancer

It's also recently been found that people who have a BRCA2 mutation, one of the mutations found in people with genetic breast cancer, are at a higher risk of developing lung cancer as well. This mutation is found in roughly two percent of people of European ancestry and is inherited in an autosomal dominant fashion (if one of your parents carries the mutations, you have a 50:50 chance of inheriting it yourself).

Genes such as the BRCA genes are considered tumor suppressor genes. These genes code for proteins that repair damaged DNA in cells (from damage that may occur due to environmental exposures such as smoking, or damage that occurs in the normal metabolic processes in the body. It's thought that a series of mutations in the DNA in cells (mutations in genes that control the growth and regulation of the cell) is what leads to the development of cancer.

In addition to increasing the risk of breast cancer and ovarian cancer (among others), smokers who have a BRCA2 mutation were found to have almost twice the likelihood of developing lung cancer. (The risk of lung cancer was also higher than normal for non-smokers with the mutation.) Smokers carrying this mutation appeared to have an increased risk primarily for squamous cell lung cancer, a form of non-small cell lung cancer. At this time, there are not any specific recommendations regarding screening for people with the mutation, but those who are concerned may wish to talk to their physicians about the possibility of CT screening for lung cancer if they have any other risk factors, such as a history of smoking or exposure to radon in their home.

Other Genetic Changes and Lung Cancer Risk

The research is young, but the unveiling of the human genome is allowing researchers to look for genetic changes in addition to BRCA2 mutations that may raise lung cancer risk. It's likely, that in the future, genetic testing may give important information on who is at risk for lung cancer, so that appropriate screening and monitoring can be done.

Somatic vs Germ-Line Mutations

Talking about gene mutations and cancer can be very confusing, especially now that many people are having genetic testing done on their tumors. When molecular profiling is done on a tumor, the mutations found are usually somatic mutations, that is, mutations in the genes that occur after birth. Germ-line mutations, in contrast, are mutations that are inherited from a parent.

Race, Lung Cancer, and Heredity

Blacks with first-degree relatives who have had lung cancer have a greater risk of early-onset lung cancer than whites. This risk increases further in those who smoke.

Other Cancers and Hereditary Lung Cancer

In general, having a family history of cancer other than lung cancer does not appear to increase the risk that you will develop lung cancer. On the other side of the equation, however, those that develop more than one primary lung cancer are significantly more likely to have a genetic predisposition contributing to their cancer.

What Should I Do if I Have a Family History of Lung Cancer?

CT screening for lung cancer is an option for some people, although it's currently only recommended for those people between the ages of 55 and 74, who smoke or have quit in the past 15 years, and have at least a 30 pack-year history of smoking. Depending upon your risk factors, you and your doctor may elect to choose screening outside of these parameters. Before we despair about those genes passed on to us by Mom and Dad, we need to keep in mind that many causes of lung cancer are preventable. Quitting smoking (if you smoke), testing your home for radon, eating a healthy diet, exercising and being careful to avoid occupational causes can all help lower your risk of developing lung cancer whether you have a family history or not.