|
American Cancer Society
Lung cancer is now the leading cause of cancer deaths among men and women. In the last few years, the figure for estimated new cases of lung cancer in men has stabilized, but in women it will certainly continue to increase. The steady increases in the rates of people developing and dying from lung cancer are the delayed effects of increased smoking by Americans from the 1920s to the 1950s. (Lung cancer can take 10 to 30 years to develop.) During recent years, however, as the dangers of smoking have become clearer, fewer people are smoking. In 1976, 42 percent of adult American men and 32 percent of adult American women smoked. By 1985, those rates had fallen to 32 percent of men and 28 percent of women. Lung cancer rates are finally leveling off and actually dropping among younger age groups. In 1986 they were 29.5 percent in men and 23.8 percent in women. After 10 to 15 years of not smoking, the risk of lung cancer for the former smoker is about twice that of a person who has never smoked, but far less than the 15 to 25 times increased risk for those who continue to smoke. The best safeguard against lung cancer is never to start to smoke, or to stop immediately.
The air we inhale enters the lungs through tubes called bronchi. These branch into the smaller bronchioles and finally into tiny air sacs, the alveoli. The average lung has more than 300 million of these air sacs, providing combined surface area of more than 750 square feet for oxygen to be absorbed into the bloodstream and carbon dioxide to be expelled. To some extent our breathing apparatus can clean itself. Mucus produced by some of the cells in the bronchi traps unfamiliar material, and the movement of the cilia, tiny hair-like structures on other cells, sweeps the mucus toward the throat, where it can be coughed out. Other impurities are carried away by the blood and lymph systems.
The constant assault of cigarette smoking on the cells lining the bronchi can cause mucus-secreting cells to become enlarged and to increase the production of mucus. The cilia lining the air passages become worn away and are then unable to sweep foreign particles out of the throat. This causes what is known as "smoker’s cough." If the smoker quite at the time of these early changes, the inner surface of the bronchi can return to normal. If the smoker continues smoking, many of the air sacs can be destroyed. Smoking beyond this stage can cause the lung cells to form abnormal growth patterns that may eventually become lung cancer. A person who doesn’t smoke, but is frequently with someone who does, can also be at higher risk for developing lung cancer. Nonsmoking wives have a 35 percent higher risk of lung cancer if their husbands smoke. Children whose parents smoke are directly threatened with respiratory infections and are more likely to develop lung disease in later life.
Cancer is a group of more than 100 diseases caused by the abnormal growth of cells. Normally, the body cells divide and reproduce in an orderly manner, so that we grow, replace worn-out tissue, and repair any injuries. Sometimes, however, cells divide without control and form masses called tumors. Tumors may invade or destroy normal tissue, interfere with body functions, and require removal by surgery. Benign tumors do not spread to other parts of the body. Cancerous or malignant tumors do. By a process known as metastasis, cells break away from the original malignant tumor and spread through the lymph and blood systems to form more malignant tumors elsewhere in the body. This spread can occur rapidly or over a period of years. Lung cancers tend to spread more quickly than most types of cancer. This is because the lungs are richly supplied by the blood and lymph systems, the very systems that carry cells to other parts of the body.
CIGARETTE SMOKING. As estimated 85 percent of lung cancer cases in men and 75 percent in women are caused by cigarette smoking. Less than 10percent of lung cancers occur among nonsmokers. Risks of developing lung cancer increase with the number of years smoking, the number of cigarettes smoked each day, and the tar and nicotine contents. There are, however, no safe levels of smoking. Even smoking one-half pack a day or low-tar and nicotine cigarettes is risky. There is no such thing as a safe cigarette. PIPE AND CIGAR SMOKING. Those who smoke pipes and cigars are more likely to get lung cancer than non-smokers, but much less so than cigarette smokers. Pipe and cigar smokers also have a greater risk than nonsmokers of cancers of the mouth, esophagus and larynx. INDUSTRIAL HAZARDS. If you work around certain industrial substances, you have an increased risk of developing lung cancer. These substances include chemicals and minerals such as asbestos, nickel, chromates, coal gas, mustard gas, arsenic, vinyl chloride, and the radon by-products of uranium mining and processing. Your risk, however, may be higher if you smoke. For example, asbestos workers who also smoke increase their risks of developing lung cancer 60 times. INVOLUNTARY SMOKING. Also knows as "passive smoking" or "second-hand smoking," involuntary smoking is the breathing in of tobacco smoke by non-smokers. While the smoke breathed in by involuntary smokers is not as concentrated as that inhaled directly by smokers, it does contain the same harmful substances. Now that several studied have shown that non-smoking wives of cigarette smokers have an increased risk of lung cancer, the link between involuntary smoking and lung cancer has become more apparent. In addition to these definite risk factors, some scientists suggest that air pollution and heavy doses of radiation may also contribute to lung cancer risk. There is no proof, however, of any direct cause-and-effect relationship.
Cancers that originate in the skin, glands, or lining of internal organs (such as the lungs), are known as carcinomas. There are four main types of carcinomas of the lungs which can be further categorized as non-small or small cell cancers.
Also called oat cell carcinoma because the cells are shaped like grains of oats, this form of lung cancer accounts for 20 percent to 25 percent of lung cancers. It is the most aggressive form and the most likely to have spread by the time of diagnosis.
SQUAMOUS or EPIDERMOID. These arise from the flat, scaly cells that line the air passages. It is the most common form of lung cancer, accounting for 35 to 40 percent of all lung cancers. Squamous cell carcinoma tends to be centrally located. ADENOCARCINOMA. This type of tumor can begin in the mucus membrane of both smaller and larger bronchi. It accounts for about 25 percent of all lung cancers and is the most common form of lung cancer among women. It can also be caused by smoking, but to a lesser degree than other forms of lung cancer. LARGE CELL CARCINOMA. This is the least common form of lung cancer, accounting for only 10 percent of all cases. It usually develops in the bronchus and is characterized by large, round cells.
Lung cancer rarely gives an early warning of its presence. The earliest symptoms are likely to be so ordinary - coughing or wheezing - that they are often dismissed as minor irritants. This is especially true of the heavy smoker, long accustomed to smoker’s cough. The most common symptoms are persistent cough and blood in the sputum. Other symptoms include repeated bouts of pneumonia, weakness, weight loss, and chest pain. More advanced disease may be signalled by hoarseness, shortness of breath, swollen lymph nodes in the neck, shoulder and arm pain, difficulty in swallowing, and drooping of the upper eyelids. In many cases, patients first notice symptoms caused by the spread of the disease, rather than the primary lung cancer. These symptoms can include headaches, blurred vision, dizziness and bone pain.
Can Lung Cancer Be Detected in Those Without Symptoms?
There are a variety of methods physicians use to confirm the presence of lung cancer and to identify the type and the extent or stage of disease. An accurate diagnosis is needed to plan the best possible treatment.
1. HISTORY AND GENERAL PHYSICAL.
2. CHEST X-RAYS.
3. TOMOGRAMS.
4. CT SCANS.
5. SPUTUM CYTOLOGY.
6. BRONCHOSCOPY.
7. NEEDLE BIOPSY.
8. THORACOTOMY.
9. LYMPH NODE BIOPSY.
10. RADIONUCLIDE SCANS. Other tests are now being studied to see how useful they might be in detecting lung cancer and determining if and where it has spread. These include blood tests, MRI (Magnetic Resonance Imaging), and monoclonal antibodies. Like CT scans, MRI can build composite, three-dimensional images of sections of the body, but MRI does not use radiation. Monoclonal antibodies are specially bred proteins that may be useful in seeking out cancer cells.
Surgery, radiation and chemotherapy are the primary methods of treating lung cancer. The specific treatment depends on the patient’s general health, the type of cancer and the stage of the disease. Surgery involves removal of part of the lung or the whole lung depending on the extent of the tumor. Five-year survival rates for patients with early stages of non-small cell carcinoma varies from 40 to 50 percent. When a lung cancer is removed, an area surrounding the tumor is also removed and examined for cancer cells. Control of any remaining cells is carried out through additional treatments. Patients recovering from surgery usually need to use a machine to help them breathe in the first few days after surgery. They may need to limit their physical activity somewhat, depending on the amount of lung removed and the remaining function of the lungs as well as overall health. Radiation may be used along with surgery to deal with any remaining tumor or distant spread of the cancer. It is used in place of surgery when that treatment is not a possibility. Side effects of radiation therapy include a general feeling of tiredness that usually leaves within a week after treatment is complete, temporary dry or sore throat and scarring of the lungs. Chemotherapy is becoming more important in the treatment of lung cancer, particularly in small cell lung cancer. Combined chemotherapy has helped increase survival time for about 70 percent of patients with the early stage of this lung cancer - some to the point where they can be considered cured. For patients with other types of lung cancer, combination chemotherapy is generally used only when the cancer cannot be controlled by surgery or radiation, and the response rates tend to be lower than those seen in small cell lung cancer. Clearly newer and more effective drugs are needed. Patients with non-small cell lung cancer, when possible, are encouraged to participate in studies to develop new treatments. Side effects of chemotherapy depend on the drugs used. Some common side effects include hair loss, nausea and vomiting, changes in blood count and a feeling of tiredness.
Prevention of lung cancer is especially important because it is very difficult to detect early. By the time a diagnosis is made, two-thirds of lung cancer patients have disease that has passed the stage when it might be curable. Only 13 percent of lung cancer patients (all stages, whites and blacks) live five or more years after diagnosis. The survival rate is 33 percent for cases detected in a localized stage. Therefore, the outlook for many patients is not optimistic.
Prevention is vital to future change in patient survival. Quitting smoking or never starting is the best defense against lung cancer. However, help for chronic smokers is being evaluated. Studies are being undertaken to determine how to help high-risk populations, especially in understanding the addiction process and why smoking is so difficult for some people to give up. Cessation clinics or activities to halt the tobacco habit are part of American Cancer Society prevention plans. Young people must be convinced not to ever start smoking. Research is concentrating on chemoprevention and immunotherapy which may prove to be useful as well. Meanwhile the search continues for better ways to treat patients and offer rehabilitation.
|
