- Lung cancer is the leading cause of cancer death in men and women in the U.S. and worldwide .
- Cigarette smoking is the main risk factor for developing lung cancer.
- Passive exposure to snuff smoke can also cause lung cancer .
- The two types of lung cancer , which grow and spread in different ways , lung cancers are small cell (SCLC) and lung cancer non small cell (NSCLC ) .
- The stage of lung cancer refers to the extent to which cancer has spread in the body.
- Lung cancer treatment can involve a combination of surgery, chemotherapy and radiation therapy , as well as more recent experimental methods.
- The overall prognosis of lung cancer is poor because doctors tend not to find the disease until it is at an advanced stage. The five-year survival is 40 % to 50 % for lung cancer in early stage , but only 1 % to 5 % in advanced cancer , inoperable lung.
- Quitting smoking is the most important measure that can prevent the development of lung cancer.
Lung cancer , like all cancers, results from an abnormality in the body's basic unit of life, the cell. Normally, the body maintains a system of checks and balances on cell growth so that cells divide to produce new cells only when new cells are needed . Disruption of this system of checks and balances on cell growth results in an uncontrolled division and proliferation of cells that eventually forms a mass or tumor.
Tumors can be benign or malignant , and when we speak of " cancer," we refer to those tumors that are malignant. Benign tumors can usually be removed and do not spread to other parts of the body. Malignant tumors, on the other hand , grow aggressively and invade other tissues of the body , allowing the entry of tumor cells into the bloodstream or lymphatic system , and then to other sites in the body. This process of spread is termed metastasis; areas of tumor growth at these distant sites are called metastases . Since lung cancer tends to spread or metastasize very early after it forms, it is a life-threatening cancer and one of the very most difficult cancers to treat. While lung cancer can spread to any organ in the body, certain places - particularly the adrenal glands, liver , brain, and bone - are the most common sites of metastases from lung cancer.
The lung is also a very common site for metastasis from tumors in other parts of the body. Metastatic tumors are composed of the same type of cells as the original (primary) tumor . For example, if prostate cancer spreads via the bloodstream to the lungs , it is metastatic prostate cancer in the lung and is not lung cancer .
The main function of the lungs is to exchange gases between the air we breathe and the blood. Through the lungs , carbon dioxide is removed from the blood circulation and the oxygen from inhaled air enters the bloodstream . The right lung has three lobes, while the left lung has two lobes and a small structure called the lingula that is the equivalent of the right middle lobe. The main roads entering the lungs are the bronchi, which arise from the trachea. The bronchi branch into progressively smaller called bronchioles that end in tiny sacs called alveoli where gas exchange occurs airways. The lungs and chest wall are covered with a thin layer of tissue called the pleura.
Lung cancers can arise in any part of the lung , but 90 % to 95 % of lung cancers are thought to arise from epithelial cells, the cells lining the larger and smaller airways (bronchi and bronchioles ) for this reason , lung cancers are sometimes called bronchogenic cancers or bronchogenic carcinoma. ( Carcinoma is another term for cancer. ) Cancers can also arise from the pleura (called mesotheliomas ) or rarely from supporting tissues within the lungs , for example , blood vessels .
How common is lung cancer ?
Lung cancer is the most common cause of cancer death in men and women worldwide . Statistics from the American Cancer Society estimates that 228,000 new cases of lung cancer will be diagnosed in the U.S. and around 159,000 deaths from lung cancer would occur in 2013. According to the National Cancer Institute U.S. Approximately one in 14 men and women in the U.S. will be diagnosed with lung cancer at some point in their lives.
Lung cancer is predominantly a disease of the elderly , and nearly 70 % of people diagnosed with lung cancer are over 65 years of age, while less than 3% of lung cancers occur in people under 45 years old .
Lung cancer was not common prior to the 1930s but increased dramatically over the following decades snuff smoking increased. In many developing countries, the incidence of lung cancer is beginning to fall following public education about the dangers of cigarette smoking and the introduction of effective programs to stop smoking. However, lung cancer remains one of the most common cancers in men and women worldwide . In U.S. , Lung cancer has surpassed breast cancer is the most common cause of cancer death in women.
smoking
The incidence of lung cancer is strongly correlated with cigarette smoking , with about 90% of lung cancers arising as a result of the use of snuff . The risk of lung cancer increases with the number of cigarettes smoked and there was the time that smoking, doctors refer to this risk in terms of pack-years of smoking history (number of packs of cigarettes smoked per day multiplied by the number of years smoked). For example , a person who has smoked two packs of cigarettes per day for 10 years has a history of 20 pack-year smoking . While the risk of lung cancer is increased with even a history of smoking 10 pack years old, those with a history of 30- pack- years or more are considered to have the greatest risk for developing lung cancer. Among those who smoke two or more packs of cigarettes per day , one in seven will die of lung cancer.
Pipe and cigar smoking can also cause lung cancer , although the risk is not as high as in cigarette consumption . So while a person who smokes a pack of cigarettes per day has a risk for developing lung cancer is 25 times higher than a nonsmoker , pipe and cigar smokers have a risk of lung cancer that is approximately five times that of a nonsmoker.
Snuff smoke contains over 4,000 chemical compounds, many of which have proven to be carcinogenic or carcinogenic. The two primary carcinogens in snuff smoke are chemicals known as nitrosamines and polycyclic aromatic hydrocarbons . The risk of developing lung cancer decreases each year following smoking cessation as normal cells grow and replace damaged cells in the lung. In former smokers , the risk of developing lung cancer begins to approach that of a nonsmoker about 15 years after quitting.
Passive smoking
Passive smoking or inhaling snuff smoke by non-smokers sharing living or working quarters with smokers , is also an established risk factor for the development of lung cancer. Research has shown that non-smokers living with a smoker have a 24% increase in the risk of developing lung cancer compared with nonsmokers who do not live with a smoker. The risk appears to increase with the degree of exposure (number of years exposed and the number of cigarettes smoked per partner households). It is estimated that 3,000 deaths from lung cancer occur each year in the U.S. are attributable to passive smoking.
Asbestos fibers
Asbestos fibers are silicate fibers that can persist for a lifetime in lung tissue following exposure to asbestos. The workplace is a common source of exposure to asbestos fibers , as asbestos was widely used in the past as both thermal and acoustic insulation. Today, asbestos use is limited or banned in many countries , including the U.S. Both lung cancer and mesothelioma (cancer of the pleura of the lung and the lining of the abdominal cavity called the peritoneum ) are associated with exposure to asbestos. Cigarette smoking drastically increases the chance of developing lung cancer associated with asbestos in workers exposed to asbestos. Asbestos workers who do not smoke have a fivefold greater risk of developing lung cancer than nonsmokers , but asbestos workers who smoke have a risk that is fifty to ninety times greater than nonsmokers .
Radon gas
Radon gas is a naturally occurring radioactive gas that is a natural decay product of uranium . Uranium decays to form products , including radon, that emit a type of ionizing radiation. Radon gas is a known cause of lung cancer, with an estimated 12 % of lung cancer deaths attributable to radon gas , or approximately 20,000 deaths related lung cancer each year in the U.S. , So that radon in the second leading cause of lung cancer in the U.S. As with asbestos exposure , concomitant smoking greatly increases the risk of lung cancer with radon exposure . Radon gas can travel up through soil and enter homes through gaps in the foundation, pipes, drains , or other openings . The Environmental Protection Agency U.S. estimated that one in every 15 homes in the U.S. contains dangerous levels of radon gas . Radon gas is invisible and odorless , but it can be detected with simple test kits .
familial predisposition
While the majority of lung cancers are associated with the use of snuff, the fact that not all smokers develop lung cancer finally suggests that other factors , such as the individual's genetic susceptibility , may play a role in the cause of lung cancer . Numerous studies have shown that lung cancer is more likely to occur in smokers and nonsmokers from the familiar to those who have had lung cancer than in the general population. A study in non-smokers showed that a genetic change in one region on chromosome 13 was associated with an increased risk of developing non-small cell lung cancer. A large lung involving more than 10,000 people from 18 countries and led by the International Agency for Research on Cancer ( IARC) cancer genetic study identified a small region in the genome (DNA ) containing genes that appear to confer increased susceptibility to lung cancer in smokers. The specific genes , located on the q arm of chromosome 15 , coding for proteins that interact with the nicotine and other toxins of snuff ( genes of nicotinic acetylcholine receptor ) .
lung diseases
The presence of certain diseases of the lung, chronic obstructive pulmonary disease including (COPD ), is associated with an increased risk (four to six times the risk of a nonsmoker ) for the development of lung cancer even after the effects concomitant cigarette smoking are excluded . Pulmonary fibrosis (scarring of the lung) appears to increase the risk about seven times , and this risk appears to be unrelated to smoking.
Prior history of lung cancer
Survivors of lung cancer have a greater risk of developing a second lung cancer than the general population have of developing a first lung cancer. Survivors of non-small cell lung cancers ( NSCLCs , see below) have an additional risk of 1% -2 % per year for developing a second lung cancer. In survivors of small lung cancer cells ( SCLCs , see below) , the risk for development of second lung cancers approaches 6% per year .
Air pollution
Air pollution from vehicles, industries and power plants can raise the likelihood of developing lung cancer in exposed individuals . Up to 1% of lung cancer deaths are attributable to breathing polluted air , and experts believe that prolonged exposure to highly polluted air may carry a risk for the development of similar to that of passive smoking lung cancer.
What are the signs and symptoms of lung cancer?
Symptoms of lung cancer are varied depending upon where and how widespread the tumor. Warning signs of lung cancer are not always present or easy to identify. Lung cancer may not cause pain or even no symptoms at all in some cases. A person with lung cancer may have the following kinds of symptoms :
No symptoms : In up to 25 % of people who get lung cancer , the cancer is first discovered on a routine chest x-ray or CT scan as a solitary small mass sometimes called a coin lesion , as a two-dimensional x-ray or CT scan, the round tumor looks like a coin. These patients with small , single masses often report no symptoms at the time the cancer is discovered .
Symptoms related to the cancer: The growth of the cancer and invasion of lung tissues and surrounding tissue may interfere with breathing, leading to symptoms such as cough , shortness of breath , wheezing , chest pain and coughing up blood ( hemoptysis) . If the cancer has invaded nerves , for example , it may cause shoulder pain that travels down the outside of the arm (called Pancoast 's syndrome) or paralysis of the vocal cords leading to hoarseness. Invasion of the esophagus may lead to difficulty swallowing ( dysphagia) . If a large airway collapse of a portion of the lung may occur and cause infection ( abscesses , pneumonia ) in the blocked area is obstructed.
Symptoms related to metastasis : Lung cancer that has spread to the bones may produce excruciating pain at the sites of bone involvement . Cancer that has spread to the brain may cause a number of neurologic symptoms that may include blurred vision , headaches , seizures, or symptoms of stroke such as weakness or loss of sensation in parts of the body.
Paraneoplastic symptoms : lung cancers are often accompanied by symptoms that result from the production of hormone-like substances by the tumor cells . These paraneoplastic syndromes occur most commonly with SCLC but may be seen with any tumor type . A common paraneoplastic syndrome associated with SCLC is the production of a hormone called adrenocorticotropic hormone (ACTH ) by the cancer cells , leading to oversecretion of the hormone cortisol by the adrenal glands (Cushing's syndrome ) . The most common paraneoplastic syndrome seen with NSCLC production is similar to parathyroid hormone , resulting in elevated levels of calcium in the bloodstream substance .
Nonspecific symptoms : Nonspecific symptoms seen with many cancers , including lung cancers , include weight loss , weakness and fatigue. Psychological symptoms such as depression and mood changes are also common.
When should you see a doctor ?
One should consult a health professional if he or she develops the symptoms associated with lung cancer , particularly if they have
- a new persistent cough or worsening of an existing chronic cough
- bloody sputum
- persistent bronchitis or repeated respiratory infections
- chest pain
- unexplained weight loss and / or fatigue
- difficulty breathing and shortness of breath or wheezing
How can you prevent lung cancer?
Cessation of smoking and eliminate exposure to snuff smoke is the most important measure that can prevent lung cancer. Many products, such as nicotine gum, nicotine sprays, or nicotine inhalers, may be useful for people trying to quit smoking. Minimizing exposure to passive smoking is also an effective preventive measure. Using a radon test kit at home can identify and allow correction of increased radon levels in the home. Methods that allow early detection of cancers, such as computed tomography helical low dose, may also be of value in identifying small cancers that can be cured by surgical resection and prevented from becoming widespread, incurable metastatic cancer.
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