Lung cancer is an abnormal growth of cells in the lungs, usually caused by smoking cigarettes, that frequently spreads to other parts of the body and is often fatal.
In the 1960s, actor David McLean was hired to portray the Marlboro Man, a macho, cigarette-smoking cowboy, in television and print advertising for the tobacco company Philip Morris. McLean smoked many packs of cigarettes to get the right, ruggedly handsome look for each ad, and later he continued to receive boxes of cigarettes as gifts from the company. McLean had begun smoking at age 12, and he never was able to quit. In 1985 he began to suffer from a lung condition called emphysema * due to smoking, and in 1993 he was diagnosed with cancer of the right lung. By 1995 the cancer had spread to his brain and spine. McLean died that year at age 73.
Lung cancer is the world's top cancer killer, accounting for 1.59 million deaths each year. According to the American Lung Association, more than 50 percent of lung cancer patients die within one year of diagnosis, and the five-year survival rate is just 17.8 percent. The single biggest cause of lung cancer is cigarette smoking.
Lung cancer may start in the lining of the bronchi, in the trachea, or in the lungs. The disease takes a long time to develop. Lung tissue, like every other kind of body tissue, contains DNA * . DNA is a molecule that carries all the chemical instructions living organisms need to develop, grow, and function. Discrete sequences of DNA are the genes * that are inherited from an individual's parents and that code for all the functions of every cell in the body. Gene changes, called mutations, can cause normal cells in the lungs to behave abnormally and to form cancers. These changes are DNA coding errors that can occur when a cell copies its DNA in preparation for the cell division that produces two new cells. Then both new cells carry the abnormal coding instructions. Some genes tell cells when to grow, and others tell them when to stop growing. Mutations in these genes may tell cells to grow too much, or they may fail to tell them to stop growing. In either case, the result is cells that are out of control. The cells have repair mechanisms to correct the faulty signals, but when a cell is growing very fast, errors may slip past.
Most of the mutations that occur in lung cancer are not believed to be changes that are inherited from a person's parents. Instead, the mutations seem to occur during the person's lifetime in response to environmental factors. It is possible for a person to inherit a reduced ability to break down certain kinds of cancer-causing chemicals and therefore be more likely to develop mutations. Because cases of lung cancer sometimes cluster in families, scientists think some lung cancers may develop due to a combination of genes and cigarette smoking. In other words, people who have inherited certain genes that are vulnerable to developing coding errors and who also smoke might be more likely to develop lung cancer than other people who smoke but do not have those genes. The specific genetic factors that increase the risk for lung cancer are not clear. Several scientific studies have identified inherited gene variations that may increase the risk of lung cancer in people who smoke or have been exposed to various environmental agents; however, as of 2015 no particular gene or set of genes has been established as the definite risk factor in all people.
More people die from lung cancer each year than from any other kind of cancer. The rates of death from lung cancer vary by state. These differences in death rates in the states correspond to cigarette smoking trends: states with higher rates of cigarette smoking have higher rates of death from lung cancer. In addition, according to the American Cancer Society, the states with the highest death rates from lung cancer were states without strong public health programs that discouraged tobacco use. In the 1990s the death rate from lung cancer in people 30 to 39 years of age fell by 19 percent in California and 28 percent in Oregon after those states developed strong antitobacco programs. During those same years, the rate of death from lung cancer increased in states with weak antitobacco programs, including West Virginia, Kentucky, and Missouri. In 2011 the state with the highest rate of lung cancer was Kentucky, and with the lowest was Utah.
More than 80 percent of lung cancer cases are caused by smoking. Tobacco smoke damages cells in the lungs of smokers in ways that can lead to cancer. Smokers are 10 times more likely than nonsmokers to get lung cancer, and the longer a person has been smoking, the greater the risk. Breathing secondhand smoke, the smoke given off by burning cigarettes or exhaled by smokers, causes about 3,400 lung cancer deaths each year. At least 15,000 deaths from lung cancer each year are caused by radon gas. Radon occurs naturally in soil and rocks that contain uranium. Radon gas seeps into homes through cracks and other openings. As of 2016, the U.S. Environmental Protection Agency (EPA) estimates that one out of every 15 homes has unsafe levels of radon. Radon in homes cannot be seen or smelled, but it can be measured with a simple test kit.
People who have worked with asbestos, a substance once widely used as an insulating material that was later banned in the workplace and in home products, also have a higher risk of getting lung cancer. Other risk factors for the disease include cancer-causing chemicals in the workplace. In 2015 researchers determined that about 10 to 20 percent of people diagnosed with lung cancer have never smoked nor been exposed to other known risk factors. Medical researchers theorize that these cases of lung cancer are related to unknown environmental risk factors and to genetic causes.
Symptoms of lung cancer often do not appear until the disease is advanced. Many times, the cancer is discovered when a person gets a chest x-ray for an unrelated reason. When symptoms do occur, they are so general that many conditions could cause them. Possible symptoms include a cough that does not go away, chest pain, hoarseness, bloody sputum *
The doctor will perform a physical exam and, if lung cancer is suspected, will probably order a chest x-ray. The doctor may also take a sample of sputum to be examined for abnormal or cancerous cells. In addition, if a tumor * is found on the x-ray, the doctor can perform a biopsy * of the lung tissue. This procedure uses special instruments to remove a small sample of abnormal tissue from the lung for examination under a microscope.
First, tests are done to find out how advanced the cancer is and if it has spread. Based on these tests, the cancer is usually assigned a Roman numeral from I to IV. This process is called staging. The smaller the number, the less the cancer has spread. The larger the number, the more it has spread and the more serious the disease. This system is used for most types of lung cancer, including the types called squamous cell cancer, large cell cancer, and adenocarcinoma (ah-DEE-noh-kar-si-no-mah). One-fourth of lung cancers are a type called small cell lung cancer. Instead of getting a Roman numeral, this type is rated as either limited (not widespread) or extensive (in both lungs, for example, and spread to distant organs).
The best treatment for lung cancer is determined by the type of cancer, the stage, and the person's overall health. Treatment usually consists of a combination of surgery, chemotherapy, and radiation therapy.
For cancer that has not spread, surgery offers the chance of a cure by removing the diseased part of the lung. Some tumors, however, cannot be removed by surgery due to their size or location, and some patients cannot have surgery for other health reasons.
Chemotherapy is the use of anticancer drugs to kill cancer cells. The drugs are given intravenously (into a vein) or orally (as pills). Because these drugs enter the bloodstream and can reach all areas of the body, they may be useful for treating cancer that has spread beyond the lungs. Chemotherapy can have side effects, including nausea (a feeling of wanting to throw up) and hair loss. Not everyone reacts to chemotherapy in the same way. Usually, the side effects disappear and hair begins to grow back when the treatment is over.
Radiation therapy is the use of high-energy x-rays to kill or shrink a tumor. In lung cancer patients who are not healthy enough for surgery, radiation may be the main treatment. For other patients, radiation may be used after surgery to kill small areas of cancer cells too tiny to be seen during surgery. Radiation can make a person feel tired, and the skin in the treated area may look first sunburned, then tan. The skin eventually returns to normal.
The best way to prevent lung cancer is by not smoking. People who do not smoke should not start, and people who do smoke should quit. Because the nicotine in cigarettes is so addicting, it is not easy to quit, but it is well worth the effort. Simply switching to “low tar” or filtered cigarettes does not prevent cancer, nor does it diminish the addictive properties of nicotine. People should also avoid breathing in other people's smoke. In addition, people can test their homes for radon, find out whether cancer-causing chemicals are used in their workplace, and take steps to protect themselves.
Researchers are looking at new approaches to chemotherapy, surgery, and radiation, and they are trying to find the best combinations of therapies. For example, chemotherapy followed by surgery and radiation helps some patients live longer. Giving two types of chemotherapy at the same time or giving chemotherapy and radiation at the same time, instead of sequentially, is another promising approach. In the early 2000s, studies were testing a type of radiation therapy in which smaller doses are given more often in hopes of killing more cancer cells. Treatments that help the patient's immune system * fight lung cancer more effectively were also a focus of research. By 2015 this socalled immunotherapy had shown great promise in the treatment of lung cancer. The Food and Drug Administration (FDA) approved three new drug treatments in that year that help the patient's immune system target and kill cancer cells and significantly extend life. In addition, for some patients with identified gene variations who have non–small cell lung cancer or adenocarcinoma, targeted therapy drugs that target a part of the cancer cell and interfere with its ability to divide and grow became available in 2014. The treatment has had remarkable success and has worked better than chemotherapy for people with the specific gene variations. In some cases, the cancers have disappeared, at least for the time being. In 2016 many other kinds of targeted therapies and immunotherapies were being tested in clinical trials around the world, but the effects of these new treatments on future survival and mortality rates were not yet known. In addition, gene therapy * may one day be able to repair the genetic mutations that lead to lung cancer.
Prevention still offers the greatest chance for fighting lung cancer despite the success of the latest treatment breakthroughs. The best prevention is not to start smoking, but if people do smoke, then the best choice is for them to quit.
Because of the low rate of cure, lung cancer patients typically have concerns about whether the cancer will come back after treatment and how long they will live. People need their lungs to breathe, so in advanced cases, as the cancer takes up more and more of the space usually occupied by air, breathing becomes difficult. In addition, growth of the cancer around certain nerves may cause severe pain. Medications can relieve this pain, and patients should not hesitate to ask for them.
See also Cancer: Overview • Tobacco-Related Diseases: Overview • Tumor
Addario, Bonnie J., et al. Navigating Lung Cancer: 360 Degrees of Hope, 2nd ed. Seattle: CreateSpace Independent Publishing Platform, 2015.
Mukherjee, Siddhartha. The Emperor of All Maladies: A Biography of Cancer. New York: Scribner, 2010.
American Cancer Society. “Lung Cancer.” http://www.cancer.org/cancer/lungcancer/index (accessed March 13, 2016).
American Cancer Society. 250 Williams St. NW, Atlanta, GA 30303. Toll-free: 800-227-2345. Website: http://www.cancer.org (accessed March 13, 2016).
American Lung Association. 55 W. Wacker Dr., Suite 1150, Chicago, IL 60601. Toll-free: 800-586-4872. Website: http://www.lung.org (accessed March 13, 2016).
National Cancer Institute. 9609 Medical Center Dr., Bldg. 9609, MSC 9760, Bethesda, MD 20892-9760. Toll-free: 800-422-6237. Website: http://www.cancer.gov (accessed March 13, 2016).
* emphysema (em-fuh-ZEE-mah) is a lung disease in which the tiny air sacs in the lungs become permanently damaged and are unable to maintain the normal exchange of oxygen and other respiratory gases with the blood, often causing breathing difficulty.
* DNA or deoxyribonucleic acid (dee-OX-see-ry-bo-nyoo-klay-ik) is the specialized chemical substance that contains the genetic code necessary to build and maintain the structures and functions of living organisms.
* genes (JEENS) are specific segments of deoxyribonucleic acid (DNA) that help determine a person's body structure, physical characteristics, and other traits. Inherited from a person's parents, genes are contained in the chromosomes found in the body's cells.
* sputum (SPYOO-tum) is a substance that contains mucus and other matter coughed out from the lungs, bronchi, and trachea.
* tumor (TOO-mor) is an abnormal growth of body tissue that has no known physiologic purpose. A tumor may or may not be cancerous.
* biopsy (BI-op-see) is a test in which a small sample of skin or other body tissue is removed and examined for signs of disease.
* immune system (im-YOON) is the system of the body composed of specialized cells and the substances they produce that helps protect the body against disease-causing germs.
* gene therapy is a treatment that works by altering genes.