Lung cancer is not just one disease but rather a group of diseases. All forms of cancercause cells in the body to change and grow out of control. Most types of cancer cells forma lump or mass called a tumor.
Cells from the tumor can break away and travel to otherparts of the body where they can continue to grow. This spreading process is calledmetastasis. When cancer spreads, it is still named after the part of the body where itstarted. For example, if breast cancer spreads to the lungs, it is still breast cancer, not lungcancer. Another word for cancerous is malignant, so a cancerous tumor is referred to asmalignant.
But not all tumors are cancer. A tumor that is not cancer is called benign. Benign tumors do not grow and spread the way cancer does. They are usually not a threatto life. A few cancers, such as blood cancers (leukemia), do not form a tumor.
Mostcancers are named after the part of the body where the cancer first starts. Lung cancerbegins in the lungs. The lungs are two sponge-like organs in the chest. The right lung hasthree sections, called lobes.
The left lung has two lobes. It is smaller because the hearttakes up more room on that side of the body. The lungs bring air in and out of the body,taking in oxygen and getting rid of carbon dioxide gas, a waste product. The lining aroundthe lungs, called the pleura, helps to protect the lungs and allows them to move duringbreathing.
The windpipe (trachea) brings air down into the lungs. It divides into tubescalled bronchi, which divide into smaller branches called bronchioles. At the end of thesesmall branches are tiny air sacs known as alveoli. Most lung cancers start in the lining ofthe bronchi but they can also begin in other areas such as the trachea, bronchioles, oralveoli.
Lung cancer often takes many years to develop. Once the lung cancer occurs,cancer cells can break away and spread to other parts of the body. Lung cancer is a life-threatening disease because it often spreads in this way before it is found. Lung cancer isthe leading cause of cancer death for both men and women.
During the year 2000 therewill be about 164,100 new cases of lung cancer in this country. About 156,900 people willdie of lung cancer: about 89,300 men and 67,600 women. More people die of lung cancerthan of colon, breast, and prostate cancers combined. Lung cancer is fairly rare in peopleunder the age of 40. The average age of people found to have lung cancer is 60.
If lungcancer is found and treated by surgery early, before it has spread to lymph nodes or otherorgans, the five-year survival rate is about 42%. However, few lung cancers are found atthis early stage. The five-year survival rate for all stages of lung cancer combined was14% in 1995, the last year for which we have national data. A risk factor is something thatincreases a person’s chance of getting a disease. Some risk factors, like smoking, can becontrolled. Others, such as a person’s age, can’t be changed.
Smoking is by far the leadingrisk factor for lung cancer. More than 8 out of 10 lung cancers are thought to result fromsmoking. The longer a person has been smoking, and the more packs per day smoked, thegreater the risk. If a person stops smoking before lung cancer develops, the lung tissueslowly returns to normal. Stopping smoking at any age lowers the risk of lung cancer. Cigar and pipe smoking are almost as likely to cause lung cancer as cigarette smoking.
There is no evidence that smoking low tar cigarettes reduces the risk of lung cancer. Nonsmokers who breathe the smoke of others also increase their risk of lung cancer. Non-smoking spouses of smokers, for example, have a 30% greater risk of developing lungcancer than do spouses of nonsmokers. Workers exposed to tobacco smoke in theworkplace are also more likely to get lung cancer. There are other risk factors for lungcancer besides smoking. People who work with asbestos have a higher risk of getting lungcancer.
If they also smoke, the risk is greatly increased. The type of lung cancer linked toasbestos, mesothelioma, often starts in the pleura. This
