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Genetic Testing for People with Lung Cancer

Understanding Molecular Profiling

By Lynne Eldridge MD

Updated March 31, 2014

Written or reviewed by a board-certified physician.

Gene Mutations in Lung Cancer

One of the most exciting advances in the treatment of lung cancer has come from an understanding of genetic changes in lung cancer cells. Whereas in the past we broke lung cancers down into perhaps 5 types, we now know that no two lung cancers are the same. If there were 30 people in a room with lung cancer, they would have 30 different and unique types of lung cancer.

If you’ve been recently diagnosed with lung cancer, especially lung adenocarcinoma, your oncologist may have talked to you about genetic testing (otherwise known as molecular profiling or biomarker testing) of your tumor. It's now recommended that all lung cancer patients with advanced or metastatic lung adenocarcinoma (a type of non-small cell lung cancer) have biomarker testing to look for EGFR mutations and ALK rearrangements. In addition, non-smokers with other forms of non-small cell lung cancer should be considered for testing. What does this mean?

What is Genetic Testing (Molecular Profiling) of a Lung Cancer Tumor?

Genetic testing involves tests that a pathologist performs in the lab using a sample of your cancer tissue - tests that look at the cancer from a molecular level. This tissue may come from a biopsy of your tumor, or from tissue removed during surgery for lung cancer. The reason behind this is that cancers have gene mutations that "drive" or control the growth of the cancer. Simplistically, if these mutations can be identified, then treatments can be used which "target" these mutations, hence stopping the growth of the cancer. It is these mutations (usually a minimum of 6 or 7) that lead to the development of a cancer in the first place.

Before going further it's helpful to address something that is confusing for many people. There are two primary types of gene mutations.

Hereditary Mutations vs Aquired Mutations in Cancer

One type of mutations are hereditary mutations (also called germline mutations,) meaning you inherit genes with mutations from one or more parents. Common examples of these mutations include hemophilia, as well as mutations that may predispose someone to developing breast cancer (BRCA1 and BRCA2 mutations.)

The type of mutations that scientists look for in people with lung cancer are instead called acquired mutations (also called somatic mutations.) These mutations are not present at birth (they do not run in families) but rather develop in the process of cells becoming cancerous.

What are Cancer Cells?

Cancer Cells vs Normal Cells

What Exactly are Gene Mutations?

Gene mutations are changes to a particular gene in a chromosome. All genes are made up of 4 amino acids (called bases); adenine, tyrosine, cytosine, and guanine. When a gene is exposed to toxins in the environment, or when an accident occurs in cell division, a mutation (change) may occur. In some cases it may mean that one base is substituted for another, say adenine instead of guanine. In other cases bases may be inserted, or deleted, or genes may be rearranged in some way.

Significance of Gene Mutations

Why are oncologists interested in acquired gene mutations in a tumor? First, we should talk about the two types of acquired mutations found in lung cancers. One type of mutation is termed a driver mutation. These mutations, via several mechanisms, “drive” the growth of a tumor. It’s not known exactly how many driver mutations are present in a cancer, but estimates suggest around 1 to 10 are present in most cancers. Another type of mutation is termed a passenger mutation. Just as someone may be a passenger in a car, these genes do not drive the cancer and are basically along for the ride. Again we don’t know exactly how many passenger mutations are present in a tumor (and the number varies from tumor to tumor) but some tumors may have upwards of 100,000 passenger mutations. Interestingly some passenger mutations may actually retard the growth of a tumor.

Driver mutations not only initiate the development of a cancer, but work to maintain the growth of a cancer as well.

Common Driver Mutations Found in Lung Cancer Tumors

There are many mutations that are being studied by scientists looking at lung tumors. So far driver mutations have been found in 62% of lung adenocarcinomas. Researchers are now finding driver mutations in squamous cell lung cancer as well.

Common driver mutations in lung cancer include (for starters):

EGFR mutations

KRAS mutations

EML4-ALK Rearrangements

MET signaling

Personalized Treatments Available Based on Genetic Testing

The use of "targeted therapies" - that is medications that target particular genetic abnormalities in a tumor -- has been coined personalized medicine. What this means is that rather than a conventional chemotherapy drug that attacks all rapidly dividing cells, a targeted drug instead attacks a particular abnormality present only in cancer cells. In general targeted treatments have fewer side effects than traditional chemotherapy. To date, targeted therapies that have been approved for people with lung cancer include:

Tarceva (erlotonib) has been approved for people whose tumor has an EGFR mutation (note: there are different types of EGFR mutations)

Xalkori (crizotonib) was approved by the FDA in 2011 for people whose tumor has an ALK4-EML gene rearrangement

Other medications are being studied in clinical trials, including targeted therapies for those whose tumor becomes resistant to Tarceva or Xalkori..

A challenging problem with current treatments is that nearly everyone inevitably becomes resistant to treatments we have. There are many mechanisms by which this occurs making it difficult to find one solution. Research is ongoing in clinical trials; evaluating both the use of substituting a second drug to target the mutations, and drugs that address problems with resistance directly.

The Future

The ability to understand the molecular profile of lung tumors is an extremely exciting area of research, and it’s likely that new treatments for other mutations will soon be available. An example of how rapidly this area of medicine is advancing is the ALK4-EML gene rearrangment. This gene "mutation" (actually a rearranglement) was discovered as recently as 2007. Through a rapid process, the medication Xalkori (crizotinib) was approved in 2011 for general use by the FDA for those patients whose tumors have this rearrangment. There are clinical trials currently in progress evaluating the use of second generation drugs for those who have become resistant to Xalkori.

Next Step

If you have been diagnosed with non-small cell lung cancer, especially lung adenocarcinoma or squamous cell lung cancer, talk to your doctor about genetic testing. Although testing is now recommended for everyone with non-small cell lung cancer, a recent study reported that only 60% of oncologists are currently ordering testing. You may also wish to talk to your doctor about clinical trials that may be an option for you. If you are interested in looking into trials evaluating these treatments worldwide, check out the article below on how to find clinical trials. It can be confusing as you check out these databases, but help is near. Recently a lung cancer clinical trial matching service backed by several lung cancer organizations has become available. With this free service a trained nurse navigator can help you locate any clinical trials that may be an option for you.

Sources:

Hensing, T., Chawla, A., Batra, R., and R. Salgia. A personalized treatment for lung cancer: molecular pathways, targeted therapies, and genomic characterization. Advances in Experimental Medicine and Biology. 2014. 799:85-117.

Kim, H., Mitsudomi, T., Soo, R., and B. Cho. Personalized therapy on the horizon for squamous cell carcinoma of the lung. Lung Cancer. 2013. 80(3):249-55.

Li, T., Kung, H., Mack, P., and D. Gandara. Genotyping and genomic profiling of non-small-cell lung cancer: implications for current and future therapies. Journal of Clinical Oncology. 2013. 31(8):1039-49.

Luo, S., and D. Lam. Oncogenic driver mutations in lung cancer. Translational Respiratory Medicine. 2013. 1:6.

Villaruz, L., Burns, T., Ramfidis, V., and M. Socinski. Personalizing therapy in advanced non-small cell lung cancer. Seminars in Respiratory and Critical Care Medicine. 2013. 34(6):822-36.

http://lungcancer.about.com/od/Targeted ... Cancer.htm

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  • 6 months later...

Thank you for presenting this article in a way that is understandable. I recently had 2 lung biopsies, required for clinical trials, and was rejected from both because no genetic mutations were found. Very disappointing and frustrating. Does this happen often?

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  • 3 weeks later...

Unfortunately this is not uncommon.  Clinical trials have strict guidelines to measure success and ensure safety.  For example: if it is known that a person with a certain cancer type, mutation, or previous treatment history does not do well on that trial drug, there is no value for the researchers to allow that population into the trial.

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Not everyone that has lung cancer has a genetic mutation.  

 

From what I understand it's a little less than 20 of people with lung cancer will have an identifiable genetic mutation. The majority of patients will not have one.

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  • 4 weeks later...

Thank you for the information.  I have been tested and have the EGFR mutation.  I have not started therapy but have had surgery and will probably start therapy in the not too distant future.  I also lost my father to cancer. First lung cancer, then throat cancer.

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  • 7 months later...

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