SMOKING RELATED DISEASE 3: LUNG CANCER

Lung cancer is the most common cause of death from cancer in both men and women. It occurs most commonly between the ages of 45 and 70. Lung cancer is more common in women now than in the past because more women are smoking cigarettes.

Lung cancer that originates in the cells of the lungs is called primary lung cancer. However, cancer may also spread (metastasize) to the lung from other parts of the body. Metastatic cancers spread to the lungs most commonly from the breast, colon, prostate, kidney, thyroid gland, stomach, cervix, rectum, testis, bone, and skin (melanoma).

More than 90% of primary lung cancers start in the bronchi. Such lung cancer is called bronchogenic carcinoma. The specific types of lung cancer are small cell (oat cell) carcinoma, squamous cell carcinoma, large cell carcinoma, and adenocarcinoma. The last three types of lung cancer are often referred to as nonsmall cell lung cancers.

Alveolar cell carcinoma (a subtype of adenocarcinoma) originates in the small air sacs of the lung (alveoli). Although alveolar cell carcinoma can occur at a single site, it often develops simultaneously in more than one area of the lung.

Less common lung tumors are bronchial carcinoid (which may be cancerous or noncancerous), chondromatous hamartoma (noncancerous), and sarcoma (cancerous). Lymphoma is a cancer of the lymphatic system. It may start in the lungs or spread to them.

Causes:

• Cigarette smoking is the cause of about 90% of lung cancer cases in men and about 80% of cases in women. The greater the quantity and duration of smoking, the greater the risk of developing lung cancer. About 10 to 12% of all smokers eventually develop lung cancer.

• A small proportion of lung cancers (about 10% in men and about 5% in women) are caused by substances encountered or breathed in at work. Working with asbestos, radiation, arsenic, chromates, nickel, chloromethyl ethers, mustard gas, and coke-oven emissions has been linked with lung cancer. The risk of contracting lung cancer is greater in people who are exposed to these substances and who also smoke cigarettes. Air pollution causes about 1% of lung cancer cases. Exposure to radon gas in the home causes lung cancer in less than 1% of cases. Occasionally, lung cancers, especially adenocarcinoma and alveolar cell carcinoma, develop in people whose lungs have been scarred by other lung diseases, such as tuberculosis and fibrosis.