Research Lung cancer is the uncontrolled growth of abnormal cells in the lung. Normal lung tissue is made up of cells that are programmed by genes to create lung tissue in a certain shape and to perform certain functions. Lung cancer develops when the genetic material responsible for production of lung cells is damaged (genetic mutations). Repeated exposure to carcinogens such as tobacco smoke may cause damage in lung cells.
While tobacco, is the leading cause of lung cancer, some other carcinogens linked to lung cancer include radon and asbestos. These mutations in the genetic material of the lung cells cause the instructions for those cells to go askew. Consequently, those cells and their offspring reproduce wildly, without regard for the normal shape and function of a lung. That wild reproduction causes the formation of tumors that block air passages in the lung and make it stop functioning as it should.
Lung cancer is usually divided into two major types. The first type is small cell lung cancer (SCLC). The second type is non-small cell lung cancer NSCLC. Sometimes a lung cancer may have characteristics of both types. This is called mixed small cell / large cell carcinoma. About 20% of all lung cancers are is small cell lung cancer (SCLC).
It is named for the size of the cancer cells. Although each of the cells is small, they can multiply quickly and form large tumors, and can spread to lymph nodes and other organs such as the bones, brain, adrenal glands, and liver. This type of cancer often starts in the bronchi and toward the center of the lungs. Smoking almost always causes small cell lung cancer. It is very rare for someone who has never smoked to have small cell lung cancer. Other names for SCLC are oat cell carcinoma and small cell undifferentiated carcinoma.
Nonsmall cell (NSCLC) represents 75% to 80% of all cases of lung cancer and includes three distinct types of lung cancer: squamous cell carcinoma, adenocarcinoma, and large cell carcinoma. These subtypes are grouped together and called “nonsmall cell lung cancer” because their pattern of spread and their treatment differ from small cell lung cancer, and when diagnosed at an early stage, may have the potential to be cured by surgery. In addition to the two main types of lung cancer, other tumors can occur in the lungs. Some of these are non-cancerous (benign) and others are cancerous (malignant). Carcinoid tumors of the lung account for less than 5% of lung tumors. Most are slow-growing tumors.
They are generally cured by surgery. Although some carcinoid tumors can spread, they usually have a better prognosis than small cell or non-small cell lung cancer. Refer to the American Cancer Society document “Lung Carcinoid Tumors” for more information. Tobacco smoke is recognized as the number one cause of lung cancer.
Tobacco and the additives in cigarettes and cigars contain carcinogens. They also contain addictive substances that keep people using them. Tobacco smoking is by far the leading cause of lung cancer. Over 80% of lung cancer is caused directly by smoking and some of the rest are due to passive exposure to tobacco smoke. 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. Other risk factors for lung cancer include a family or personal history of lung cancer and exposure to cancer-causing agents in the workplace or the environment.
In addition to present and former smokers, others who are at risk include those who have been exposed to second-hand or side-stream smoke, and those exposed to environmental carcinogens such as radon and asbestos. Although lung cancers rarely result from inherited mutations of oncogenes or tumor suppressor genes, some people seem to inherit a reduced ability to detoxify (break down) certain types of cancer-causing chemicals. Lung cancer may cause a number of symptoms. A nagging cough is one of the more common symptoms and is likely to happen when a tumor is large and blocks an air passage.
Another symptom is chest, shoulder, or back pain, which feels like a constant ache that may or may not be related to coughing. Other symptoms may include shortness of breath, fatigue, weight loss, repeated pneumonia or bronchitis, coughing up blood, hoarseness, unexplained weakness in the legs, or swelling of the neck and face. Sometimes there are symptoms that seem unrelated to the lungs. The primary lung cancer may have already spread to other parts of the body.
Depending on where the cancer spreads and which organs are affected, symptoms can include pain, headaches, bleeding, weakness, bone fractures, or blood clots. As a result of the large size of the lungs, cancer may grow for many years, undetected, without causing suspicion. In fact, lung cancer can even spread outside the lungs without causing any symptoms. Early diagnosis can also be difficult because one of the most common symptoms of lung cancer, a persistent cough, is often mistaken for chronic bronchitis. During 2000, there will be about 164, 100 new cases of lung cancer (89, 500 among men and 74, 600 among women). Lung cancer will account for about 13.
4% of all new cancers. The average age of people diagnosed with lung cancer is 60; it is unusual under the age of 40. Lung cancer is the leading cause of cancer death among both men and women. There will be an estimated 156, 900 deaths from lung cancer (89, 300 among men and 67, 600 among women) in 2000, accounting for 28. 4% of all cancer deaths.
More people die of lung cancer than of colon, breast, and prostate cancers combined. Fewer men will die of lung cancer in 2000 than did in previous years. This decline is happening mostly in younger men. It probably reflects the drop in the number of young men who smoke. More women will die of lung cancer in 2000 than in previous years. The increase in their death rate is slowing, but it hasn’t begun to drop.
The one-year survival rate (the number of people who live at least one year after their cancer is diagnosed) for lung cancer was 41% in 1995, the last year for which we have national data. This had not changed in ten years. The five-year survival rate for all stages of lung cancer combined was 14% in 1995. This has not changed over many years. For people whose cancer is found and treated early with surgery, before it has spread to lymph nodes or other organs, the average five-year survival rate is about 42%. However, only 15% of people with lung cancer are diagnosed at this early, localized stage.
All these statistics are as of 4/18/2000. There are several types of treatment for lung cancer. One type of treatment is surgery. Surgery is primarily used to remove the cancerous tumor from the lung. The surgeon should be carefully selected to ensure that s / he is skilled in pulmonary (lung) or thoracic surgery. Outcomes are usually better if the surgeon frequently performs the procedure that will be required for your case.
If a lobe (section) of the lung is removed, it is called a lobectomy. If the entire lung is removed, the surgery is called a pneumonectomy. Removing part of a lobe is known as a segmentectomy or wedge resection. These operations involve general anesthesia (the patient is “asleep”) and a thoracotomy, making a surgical incision in the chest. Another type is chemotherapy.
Chemotherapy refers to drugs that are used to treat cancer. These drugs are taken orally or intravenously and circulate throughout the bloodstream. Chemotherapy drugs kill cancer cells as they travel through the bloodstream and into all the organs of the body. But, because they reach all the parts of your body, they also affect normal cells.
Since cancer cells usually divide faster than normal cells, they are more likely to be damaged and destroyed by these drugs. Thus the drugs may kill the cancer cells or at least control the growth and spread of the tumor. Many clinical trials are in progress to test new chemotherapy drugs. Some studies are testing whether the effectiveness of drugs known to be active against lung cancer can be improved by combining them with each other. Another type is radiation therapy. Radiation therapy uses high-energy radiation to kill cancer cells.
External beam radiation therapy uses radiation delivered from outside the body that is focused on the cancer. This is the type of radiation therapy most often used to treat a primary lung cancer or its metastases to other organs. Radiation therapy can be used alone or in combination with surgery or chemotherapy. It may be used before surgery to shrink a tumor. After surgery it may be used to stop the growth of any cancer cells that remain. In some cases, radiation therapy and chemotherapy are used together instead of surgery.
The best way to prevent lung cancer is to not smoke or be around people who do. People should not start smoking, and those who already smoke should quit. Everyone should avoid breathing in other people’s smoke. People should find out about cancer-causing chemicals that they might be exposed to at work and take appropriate protective measures. People who live in areas where natural uranium deposits in the soil release radon gas may consider testing radon levels in their homes. Nevertheless, some people who get lung cancer do not have any apparent risk factors.
Although we know how to prevent over 80% of lung cancers, at this time, it is not possible to give advice on how to prevent all cases of lung cancer.