Lung Cancer Health Article

Definition

Lung cancer is a disease in which the cells of the lung tissues grow uncontrollably and form tumors. It is the leading cause of death from cancer among both men and women in the United States. The American Cancer Society estimates that in 2001 at least 169,500 new cases of lung cancer will be diagnosed, and that lung cancer will account for 28% of all cancer deaths—approximately 157,400 people.

Types of lung cancer

There are two kinds of lung cancers, primary and secondary. Primary lung cancer starts in the lung itself. Primary lung cancer is divided into small cell lung cancer and non-small cell lung cancer, depending on how the cells look under the microscope. Secondary lung cancer is cancer that starts somewhere else in the body (for example, the breast or urinary bladder) and metastasizes (spreads) to the lungs. Identifying the type of lung cancer is important because treatment varies by type. For example, small cell cancers generally are treated with surgery. On the other hand, surgery is not generally considered beneficial for non-small cell cancers; they are treated with chemotherapy.

Small cell cancer was formerly called oat cell cancer, because the cells resemble oats in their shape. About a fourth of all lung cancers are small cell cancers. This is a very aggressive cancer and spreads to other organs within a short time. It is generally diagnosed in people who are heavy smokers. Non-small cell cancers account for the remaining 75% of primary lung cancers. They can be further subdivided into three categories.

Nearly 30% of non-small cell cancers are squamous cell carcinomas. Squamous cell carcinoma is most often found near the bronchi of patients with a history of smoking. Forty percent of non-small cell cancers are adenocarcinomas, most often found in the outer region of the lung. The remaining 10% are large-cell undifferentiated carcinomas. These rapidly spreading carcinomas may be found throughout the lung.

Incidence of lung cancer

Lung cancer is rare among young adults. It is usually found in people who are 50 years of age or older, the average age at diagnosis is 60. While the incidence of the disease is decreasing among white men, it is steadily rising among African-American men, and among both white and African-American women. This change is probably due to the increase in the number of smokers in these groups. In 1987, lung cancer replaced breast cancer as the number one cancer killer among women. Lung cancer is responsible for more deaths than the combined totals for cancers of the colon, breast, and prostate.

Causes

SMOKING. Tobacco smoking is the leading cause of lung cancer. Ninety percent of lung cancers can be prevented by giving up tobacco. Smoking marijuana cigarettes is considered yet another risk factor for cancer of the lung. These cigarettes have a higher tar content than tobacco cigarettes. In addition, they are inhaled very deeply—as a result, the carcinogens in the smoke are held in the lungs for a longer time.

EXPOSURE TO ASBESTOS AND TOXIC CHEMICALS.

Exposure to asbestos fibers, either at home or in the workplace, is also considered a risk factor for lung cancer. Studies show that compared to the general population, asbestos workers are seven times more likely to die from lung cancer. Asbestos workers who smoke increase their risk of getting lung cancer by 50-100 times. Besides asbestos, mining industry workers exposed to coal products or radioactive substances such as uranium, and workers exposed to chemicals such as arsenic, vinyl chloride, mustard gas, and other carcinogens also have a higher than average risk of contracting lung cancer.

ENVIRONMENTAL CONTAMINATION. High levels of radon, a radioactive gas that cannot be seen or smelled, pose a risk for lung cancer. This gas is produced by the breakdown of uranium, and does not present any problem outdoors. In the basements of some houses that are built over soil containing natural uranium deposits, however, radon may accumulate to dangerous levels. Other forms of environmental pollution (e.g., auto exhaust fumes) may also slightly increase the risk of lung cancer.

CHRONIC LUNG INFLAMMATION AND SCARRING. Inflammation and scar tissue are sometimes produced in the lung by diseases such as silicosis and berylliosis, which are caused by inhalation of certain minerals; tuberculosis; and certain types of pneumonia. This scarring may increase the risk of developing lung cancer.

FAMILY HISTORY. Although the exact cause of lung cancer is not known, people with a family history of lung cancer appear to have a slightly higher risk of contracting the disease.