Multiple: Lung Cancer

Definition
Description
Demographics
Causes and Symptoms
Diagnosis
Treatment
Prognosis
Prevention
The Future
For more information

Definition

Lung cancer is the uncontrolled growth of malignant cells in one or both lungs. There are two major types of lung cancer, small cell lung cancer (SCLC) and non-small cell lung cancer (NSCLC). NSCLC is

the more common of the two types, accounting for about 87 percent of cases. It develops in the cells of the tissues that line the lungs. SCLC, which is sometimes called oat cell cancer, accounts for the other 13 percent. It develops out of the hormone-producing cells in the lungs and grows more quickly than the NSCLC type of lung cancer. Small cell lung cancer is also more likely to spread to other parts of the body.

Both types of lung cancer may be either primary or secondary. A primary lung cancer is one that starts in the lung and metastasizes (spreads) to other parts of the body—most commonly to the adrenal glands, bones, liver, and brain. A secondary lung cancer is one that began in another organ and spread to the lungs. For example, breast cancer is a type of cancer that frequently spreads to the lungs.

Description

Lung cancer was a rare disease before smoking tobacco products became widespread; it was not even recognized as a distinct illness until 1761. It is now known to begin when tobacco smoke or some other irritant damages the cells of the lung tissue. The body can repair this damage for some time; eventually, however, the injured cells begin to multiply abnormally, forming a tumor in the lung tissue. The tumor may grow large enough to put pressure on the airway, causing the coughing and difficult breathing that are characteristic of advanced-stage lung cancer.

Another development that can occur is that the cancerous cells in the lung tissue can enter the blood and lymph vessels that supply the lungs. The circulation of the blood and lymphatic fluid can then carry the cancerous cells to other parts of the body. It is possible for the primary lung cancer to metastasize to other organs before coughing or other symptoms appear in the patient's lungs.

Many lung cancers are richly supplied with blood vessels close to the surface of the tumor. If the surface of the tumor is fragile, it may break off and cause bleeding into the airway. The blood may then be coughed up by the patient. Another complication that can develop is pneumonia. If the lung cancer is large enough to partially block the airway, mucus and tissue fluid may build up in the lung tissue behind the blockage, thus making it easier for bacteria to multiply and cause infectious pneumonia.

Demographics

Lung cancer is the leading cause of cancer deaths worldwide; about 1.3 million people die each year from the disease, 162,000 of them in the

United States. Fewer than half of newly diagnosed lung cancer patients live beyond a year after diagnosis; and only 14 percent survive for five years. Lung cancer represents 15 percent of all cancer diagnoses in North America and 29 percent of all cancer deaths.

Lung cancer is a highly preventable disease. Although some risk factors for lung cancer cannot be changed, avoiding tobacco would reduce deaths by about 80 percent. Men who smoke are twenty-three times more likely to develop lung cancer than men who have never smoked; women who smoke have a risk thirteen times greater than that of nonsmokers. In addition to active smoking, the risk factors for lung cancer include:

• Exposure to secondhand tobacco smoke. Nonsmokers who share housing or office space with heavy smokers have an increased risk of lung cancer.
• Exposure to radon. Radon is an invisible, odorless gas produced by the breakdown of uranium in soil and rock. Between 9 and 14 percent of deaths from lung cancer are caused by exposure to radon.
• Occupational exposure to asbestos, uranium, and coke (a fuel used in iron manufacturing).
• Air pollution.
• Age. Lung cancer is almost entirely a disease of older adults. The average age at diagnosis in the United States is seventy years.
• Sex. Men are more likely than women to develop lung cancer; however, the rates for women have risen sharply in recent years because of the increase in smoking among women starting in the 1960s. Nonsmoking women are more likely to develop lung cancer, however, than nonsmoking men.
• Race. African Americans of either sex are more likely to develop and die from lung cancer than any other ethnic group in the United States. On the other hand, Native Americans have one of the lowest rates. The reasons for these differences are not yet known.

• Family history. People with a parent or sibling diagnosed with lung cancer are at increased risk of developing the disease themselves even if they do not smoke.
• Personal history of bronchitis or repeated episodes of pneumonia. Some researchers think that a history of lung disease is a risk factor for eventual lung cancer.

Causes and Symptoms

The largest single cause of lung cancer is exposure to tobacco smoke, followed by such other irritants as radon, asbestos, and air pollution. The causes of lung cancer in nonsmokers are not yet fully understood. Some researchers think that damage to chromosomes 3, 5, 13, and 17 increases a nonsmoker's risk of small cell lung cancer. Another theory concerns human papillomavirus, which has been shown to cause lung cancer in animals. These scientists think that human papillomavirus (HPV, a sexually transmitted virus) infection may trigger lung cancer in some people by causing uncontrolled cell division in lung tissue.

Lung cancer often does not have symptoms in its early stages. A primary lung cancer may produce the following symptoms:

• Fatigue
• Coughing that does not go away
• Coughing up blood
• Chest pain
• Shortness of breath
• Loss of appetite and unintended weight loss
• Coughing up large quantities of mucus

A lung cancer that has spread to other organs may produce bone pain, abdominal or back pain, headache, weakness, seizures, or speech difficulties.

Diagnosis

Lung cancers are sometimes diagnosed relatively early when a person develops pneumonia and the doctor discovers a cancerous tumor. In most cases, however, the tumor is diagnosed when the person develops the symptoms of advanced-stage lung cancer.

There is no universally accepted screening test for lung cancer. Some doctors think that a newer type of computed tomography (CT) scan

called a spiral CT scan is a useful way to screen for lung cancer. In a spiral CT scan, the patient lies on a table while the scanner rotates around them. Other doctors, however, think that this test does not yet distinguish clearly enough between lung cancer and other less serious lung problems to justify using it as a screener.

The tests that are most commonly used to detect lung cancer and determine whether it is SCLC or NSCLC include:

• Imaging studies, usually a CT scan of the lungs or an x-ray image of the chest.
• Sputum sample. The patient is asked to cough up some sputum (mucus or phlegm), which can be studied under a microscope for the presence of cancer cells.
• Tissue biopsy. Samples of suspicious tissue may be obtained in one of several ways. The doctor may use an instrument called a bronchoscope(alighted tube passed down the throat and into the lungs), or make an incision at the base of the neck and remove a tissue sample from the space behind the breastbone. A third technique involves inserting a needle through the chest wall directly into the suspected tumor to remove a sample of tissue.
• Thoracentesis. This is procedure in which the surgeon inserts a needle through the chest wall in order to withdraw some tissue fluid from the space between the lung and the chest wall. As with a sputum sample, the fluid can be checked for cancer cells.

After determining whether the cancer is small cell or non-small cell in type, the next step is staging. Staging is a description of the location of the cancer, its size, how far it has penetrated into healthy tissue, and whether it has spread to other parts of the body. SCLC and NSCLC tumors are staged differently because these two types of lung cancer are treated differently.

• SCLCs are staged in two stages, limited and extensive. A limited-stage SCLC is found only in one lung and its nearby tissues. An extensive tumor is found outside the lung in which it started or in distant organs.
• NSCLCs are staged in an occult (hidden) stage, in which the cancer is detectable only in cells from a sputum sample without

• a visible tumor; and five stages graded from 0 to IV in which there is a visible tumor. The grade of the tumor is based on its size and on whether it has spread to the lymph nodes or nearby tissues. In stage 0, for example, the cancer is found only in the innermost lining of the lung. In stage IV, the cancer has spread from one lung to the other lung, or has spread to the brain, bones, liver, or other organs.

Treatment

Treatment of lung cancer depends on which type it is and its stage.

SCLCs: Limited-stage small cell lung cancers, which account for about 30 percent of those diagnosed, can usually be treated with radiation therapy. Extensive SCLCs cannot be completely treated with radiation therapy alone and usually require a combination of radiation therapy and chemotherapy.

NSCLCs: Patients diagnosed with non-small cell lung cancers may have surgery, chemotherapy, radiation therapy, or a combination of treatments. The treatment choices are different for each stage. Surgery, for example, may involve removing only a wedge-shaped portion of a lung, an entire lobe of a lung, or the complete lung.

Prognosis

The prognosis for lung cancer is poor. It has one of the lowest five-year survival rates of all cancers—about 14 percent as of 2008. For SCLCs, the overall five-year survival rate is 5 percent, with patients diagnosed with extensive disease having a five-year survival rate of less than 1 percent. The average length of survival time for patients with limited-stage disease is 20 months.

For patients with NSCLCs, those with stage I disease treated with surgery have a five-year survival rate of 67 percent; the five-year survival rate of patients with stage IV disease is less than 1 percent.

Prevention

There are some preventive measures that people can take to lower their risk of lung cancer:

• Don't smoke or quit smoking.
• Avoid secondhand smoke.

• Have the home tested for radon. The American Lung Association or the local public health authorities can provide information on radon testing.

The Future

Lung cancer is likely to be a serious health problem throughout the world as people who started smoking heavily in the 1960s are now getting to the age when lung cancer is usually diagnosed. In the United States, as of 2008 the National Institutes of Health (NIH) is conducting or sponsoring over 2,300 studies related to lung cancer.

SEE ALSO Bronchitis; HPV infection; Pneumonia; Smoking

WORDS TO KNOW

Occult: The medical term for a cancer that is too small to produce a visible tumor.

Radon: A colorless and odorless gas produced by the breakdown of uranium known to cause lung cancer.

Targeted therapy: A newer type of cancer treatment that uses drugs to target the ways cancer cells divide and reproduce or the ways tumors form their blood supply.

For more information

BOOKS

American Cancer Society (ACS). Quick Facts Lung Cancer: What You Need to Know—Now / from the Experts at the American Cancer Society. Atlanta, GA: American Cancer Society, 2007.

Gilligan, David, and Robert Rintoul. Your Guide to Lung Cancer. London, UK: Hodder Arnold, 2007.

Sheen, Barbara. Lung Cancer. Detroit, MI: Lucent Books, 2008.

PERIODICALS

Fink, Sheri. “New Therapies Aim at Lung Tumors, Case by Case.” New York Times, October 25, 2006. Available online at http://health.nytimes.com/ref/health/healthguide/esn-lungcancer-ess.html (accessed on September 28, 2008).

Grady, Denise, and Brent McDonald. “CT Screening for Lung Cancer.” New York Times, October 31, 2006. Available online at http://video.on.nytimes.com/index.jsp?fr_story=cde8a179a490d9a9fe977c6df92fb8fe3b88a538 (accessed on September 28, 2008).

WEB SITES

American Lung Association (ALA). Lung Cancer. Available online at http://www.lungusa.org/site/apps/nlnet/content3.aspx?c=dvLUK9O0E&b=2060245&content_id={6F0688E6-33A8-4323-8367-ECACED27CDDC}&notoc=1 (updated October 2007; accessed on September 28, 2008).

American Society of Clinical Oncology Cancer Net. Lung Cancer. Available online at http://www.cancer.net/patient/Cancer+Types/Lung+Cancer (updated December 2007; accessed on September 28, 2008).

Mayo Clinic. Lung Cancer. Available online at http://www.mayoclinic.com/health/lung-cancer/DS00038 (updated November 10, 2007; accessed on September 28, 2008).

National Cancer Institute (NCI). What You Need to Know about Lung Cancer. Available online at http://www.cancer.gov/cancertopics/wyntk/lung/allpages (updated July 26, 2007; accessed on September 28, 2008).

National Library of Medicine (NLM). Lung Cancer. Available online at http://www.nlm.nih.gov/medlineplus/tutorials/lungcancer/htm/index.htm (accessed on September 28, 2008).