Lung cancer refers to an uncontrolled growth of cells that starts in the lungs. The cells then cluster together to form a tumor that can spread to other sites in the body. Lung cancer is the third most common cancer in the United States (skin cancer being the first and prostate and breast cancer being the second most common cancer in men and women, respectively). Regardless of gender, lung cancer causes more deaths than any other cancer in the United States. They are also one of the commonest cancers in most developing countries. The lungs are quite vulnerable to develop cancer since they are exposed to all types of pollutants and harmful substances present in the air that we breathe. Worldwide, lung cancers cause the highest number of deaths compared with all other types of cancers.
Lung cancer occurs when any of the several cells in the lungs develop an abnormal change in its genes that control cell growth and multiplication (mutation). A mutated cell goes beyond the controlling machinery and multiplies to form more abnormal cells of its kind that grow to form a lump or mass, which can metastasize to other organs. There are various kinds of lung cancers and the exact cause may vary with each type. In some cases, the cause of lung cancer remains unknown. Several risk factors play important roles in causing lung cancer. They include:
- Smoking: It is the leading cause of lung cancer. Almost 80% of lung cancer deaths are because of smoking. Not just cigarettes, other forms of tobacco smoking, such as pipes and cigars, can also increase lung cancer risk. Smoking can increase the risk of lung cancer and lung cancer deaths by around 15 to 30 times. The risk of lung cancer increases as the number of cigarettes smoked and the years of smoking increase. Even people who smoke fewer cigarettes per day have a higher risk of lung cancer than nonsmokers. A person’s risk for lung cancer can go down if they quit smoking. The risk, however, remains higher than people who never smoked. Quitting smoking at any age can be the first step toward decreasing lung cancer risk. Tobacco smoke contains over 7000 chemicals of which at least 70 are known to cause cancers of various kinds, including cancers of the throat, food-pipe, kidney, colon, and bladder. Not all smokers get lung cancer and not all lung cancer patients are smokers. This suggests the role of other factors, such as genes, in lung cancer causation.
- Secondhand smoke: People who do not smoke but are exposed to smoke from other people’s cigars, cigarettes, or pipes are also at a higher risk of lung cancers. Over 7000 lung cancer cases are caused by secondhand smoke.
- Radon: It is a naturally occurring odorless, colorless, and tasteless gas. Radon is produced from rocks and dirt, and it can get collected in houses and buildings. Radon exposure is the second leading cause of lung cancer in the United States.
- Occupational risks: Exposure to certain substances found at the workplace, such as asbestos, chromium, nickel, tar, and diesel exhaust, can increase cancer risk. The risk is further increased in people who smoke or are exposed to secondhand smoke. Arsenic present in drinking water, especially the water from wells, can also put you at risk of lung cancer.
- Personal history of cancer: People who have had cancer of the lungs or any other sites in the body have a higher risk to get lung cancer.
- Chest radiation therapy: People who received radiation therapy to the chest in the past have a greater risk of suffering from lung cancer.
- Family history of lung cancer: If any of the first-degree relatives (parents, siblings, or children) had lung cancer, then there may be a higher risk of getting the disease.
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American Lung Association. Secondhand Smoke and Lung Cancer: What You Need to Know. https://www.lung.org/getmedia/e7205b52-6ebf-4a64-8079-08b9c0a4d0e1/secondhand-smoke-and-cancer.pdf.pdf
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