Cancer is a disease marked by the uncontrolled growth of abnormal cells. The abnormal cells may no longer do the work of normal cells, and they crowd out and destroy healthy tissue.  The rate of lung cancer cases is on the rise among women

Lung cancer is the most common cancer-related cause of death among men and women. It is the second most commonly occurring cancer among men and the third most commonly occurring cancer among women. There were more than 177,000 new cases of lung cancer in the U.S. in 1996 alone.

The rate of lung cancer cases appears to be declining among white men in the U.S., while it continues to increase among African-American men and among both white and African-American women. An estimated 158,700 Americans died due to lung cancer in 1996.

Lung cancer may also be the most tragic cancer because, in most cases, it might have been prevented. And treatment is currently limited in its effectiveness.

More than 95 percent of lung cancers belong to the group called bronchogenic carcinoma. This classification includes:

• Adenocarcinoma

• Squamous cell carcinoma

• Small cell (oat cell) carcinoma

• Large cell carcinoma

It is important to find out what kind of lung cancer a person has. The different types of carcinomas, involving different regions of the lung, may give rise to different symptoms and are treated differently.

Lung cancer takes many years to develop. However, changes in the lung can begin almost immediately upon exposure to carcinogens (cancer-causing substances). Soon after exposure begins, microscopic examination of the tissue lining the bronchi (the main breathing tubes) will reveal a few unusual cells. With continued exposure, more abnormal cells appear. These cells may be on their way to becoming cancerous and forming a tumor.

The symptoms of the cancer vary depending on several factors, including where in the lung the tumor is found. If the cancer is located in one of the bronchi, it can irritate the lining of the bronchus (one of the main airways that branches off of the trachea or windpipe) and cause a chronic cough. The cancerous area may bleed when a person coughs.

If the tumor grows larger, it may gradually fill the bronchus so that air can't pass in or out. A blocked bronchus may also cause repeated lung infections or pneumonia.

A tumor located in the outer part of the lung may not produce any symptoms until it is fairly large. Sometimes the first sign may be chest pain from the tumor growing into the lining of the lungs or the ribs and muscle of the chest wall.

A person's lungs have extensive networks of blood and lymph vessels. Cancer cells may grow into these vessels and be carried by the blood or lymph to circulate through the body. The cancer cells may then be deposited in other organs of the body. A new colony of cancer cells that started in another organ is known as metastasis.

The first site of tumor metastasis is usually the lymph nodes within the lungs and the mediastinum (the space between the two lungs in the middle of the chest).

It is possible for cancer cells that begin in other organs to spread to the lungs. These cases are very different medical problems, however. Depending on the organ of origin, such cases might be termed "primary breast cancer, metastatic to the lungs," or "primary kidney cancer, metastatic to the lungs." These cancers are ordinarily not treated with surgery or radiation therapy.

Smoking is the number one cause of lung cancer. Cigarette smoke contains more than 4,000 different chemicals, many of which are proven carcinogens, while hundreds of others increase the cancer-causing power of carcinogens.

Many of these chemicals also affect the nonsmoker inhaling "secondhand" or sidestream smoke, making "passive smoking" another important cause of lung cancer. In a 1993 report, the U.S. Environmental Protection Agency (EPA) concluded that involuntary smoking causes 3,000 lung cancer deaths in nonsmokers each year.

Sidestream smoke, with its high concentration of carcinogens, goes directly into the air from burning tobacco (cigarettes, cigars, etc.) and is inhaled by both smokers and nonsmokers.

If you smoke, you are much more likely to develop the disease; men who smoke are estimated to be 22 times more likely to develop lung cancer, while women who smoke are estimated to be 12 times more likely.

The more you smoke and the longer you smoke, the greater your risk of lung cancer. But if you stop smoking, the risk of cancer decreases steadily each year as abnormal cells are replaced by normal cells. In ten years, the risk decreases to a level that is 30 to 50 percent of the risk for people who continue to smoke. In addition, quitting smoking dramatically reduces the risk of developing other smoking-related diseases, such as heart disease and stroke, and significantly reduces the risk of serious emphysema and chronic bronchitis.

Radon, by its own action and by its interaction with cigarette smoking, is considered to be the second leading cause of lung cancer in the U.S. today. Radon is a radioactive gas that is found in the earth's rock and soil and is formed by the natural breakdown of radium, which is a radioactive product of decaying uranium.

Radon problems have been identified in every state. The EPA estimates that nearly 1 out of every 15 homes in the U.S. has indoor radon levels at or above the EPA's recommended action guideline level of four picocuries per liter of air (pCi/L) on a yearly average. Radon can be a problem in schools and workplaces, too.

Because radon is invisible and odorless, the only way to determine if you are being exposed to the gas is by measuring radon levels. In addition, exposure to radon, in combination with cigarette smoking, significantly increases the risk of lung cancer. Therefore, for smokers, exposure to radon is an even greater health risk.

Another leading cause of lung cancer is on-the-job exposure to carcinogens. Asbestos is perhaps the best known of the industrial substances associated with lung cancer, but there are many cancer-causing substances that people may deal with at work. These include asbestos, uranium, arsenic, certain petroleum products, and others.

In addition, it is important to realize that there are many different jobs that may involve exposure. Some examples are working with certain types of insulation, working in certain environments, such as with coke ovens, and repairing brakes. As is the case with radon, when exposure to job-related carcinogens is combined with smoking, the risk of getting lung cancer is sharply increased.

In its early stages and even later, lung cancer is usually silent. When symptoms occur, the cancer is often advanced. Symptoms of lung cancer include:

• Chronic cough
• Coughing up blood
• Wheezing
• Chest pain

These conditions are also symptomatic of many other lung problems; thus, when they occur, they warrant medical investigation.

When a person goes for an examination, his or her doctor will take an extensive medical history, noting any possible hazardous exposure. This is followed by a thorough physical examination. If the patient has a productive cough (a cough that produces sputum), the sputum may be examined for cancer cells.

The doctor may order a chest X-ray or specialized X-ray such as the CAT scan, which help to locate any abnormal spots in the lungs. The doctor may do a bronchoscopy to look inside the bronchial tubes and lungs. A bronchoscope is a small tube inserted through the nose or mouth, down the throat, into the bronchial tubes.

During this procedure the doctor may also obtain a biopsy or other sample of lung tissue and cells which are viewed under a microscope to determine if they are cancerous and if so, to identify the type of cancer involved. Biopsies of lung tissue or of the lymph nodes between the lungs may be performed using other techniques as well.

If you are a smoker, STOP SMOKING.

If you are a nonsmoker, make sure that your rights to a smoke-free environment are upheld.

Strive for a smoke-free environment both at home and at work.

Test your home for radon if you live in an area known to have high levels.

Ask questions about your work environment if you are exposed to industrial dusts and fumes.