Lung Cancer Causes, Symptoms And Treatment
What is Lung Cancer
Cancer of the lung, 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 known as a tumor.
Tumors can be benign or malignant; when we speak of "cancer," we are referring to those tumors that are malignant. Benign tumors usually can be removed and do not spread to other parts of the body. Malignant tumors, on the other hand, often grow aggressively locally where they start, but tumor cells also can enter into the bloodstream or lymphatic system and then spread to other sites in the body. This process of spread is termed metastasis; the 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 very life-threatening cancer and one of the most difficult cancers to treat. While lung cancer can spread to any organ in the body, certain locations -- particularly the adrenal glands, liver, brain, and bones -- are the most common sites for lung cancer metastasis.
The lung also is a very common site for metastasis from malignant tumors in other parts of the body. Tumor metastases are made up of the same types of cells as the original (primary) tumor. For example, if prostate cancer spreads via the bloodstream to the lungs, it is the metastatic prostate cancer in the lung and is not lung cancer.
The principal function of the lungs is to exchange gases between the air we breathe and the blood. Through the lung, carbon dioxide is removed from the bloodstream and oxygen enters the bloodstream. The right lung has three lobes, while the left lung is divided into two lobes and a small structure called the lingula that is the equivalent of the middle lobe on the right. The major airways entering the lungs are the bronchi, which arise from the trachea, which is outside of the lungs. The bronchi branch into progressively smaller airways called bronchioles that end in tiny sacs known as alveoli where gas exchange occurs. 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%-95% of cancers of the lung is thought to arise from the 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 carcinomas. (Carcinoma is another term for cancer.) Cancers also can arise from the pleura (called mesotheliomas) or rarely from supporting tissues within the lungs, for example, the blood vessels.
Smoking
The incidence of lung cancer is strongly correlated with cigarette smoking, with about 90% of lung cancers arising as a result of tobacco use. The risk of lung cancer increases with the number of cigarettes smoked and the time over which smoking has occurred; doctors refer to this risk in terms of pack-years of smoking history (the 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 20 pack-year smoking history. While the risk of lung cancer is increased with even a 10-pack-year smoking history, those with 30-pack-year histories or more are considered to have the greatest risk for the development of 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 also can cause lung cancer, although the risk is not as high as with cigarette smoking. Thus, while someone who smokes one pack of cigarettes per day has a risk for the development of lung cancer that is 25 times higher than a nonsmoker, pipe, and cigar smokers have a risk of lung cancer that is about five times that of a nonsmoker.
Tobacco smoke contains over 4,000 chemical compounds, many of which have been shown to be cancer-causing or carcinogenic. The two primary carcinogens in tobacco 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 cessation of smoking.
Passive smoking
Passive smoking or the inhalation of tobacco smoke by nonsmokers who share living or working quarters with smokers also is an established risk factor for the development of lung cancer. Research has shown that nonsmokers who reside with a smoker have a 24% increase in risk for developing lung cancer when compared with nonsmokers who do not reside with a smoker. The risk appears to increase with the degree of exposure (number of years exposed and number of cigarettes smoked by the household partner). It is estimated that over 7,000 lung cancer deaths occur each year in the U.S. that are attributable to passive smoking.
Symptoms of primary lung cancers include a cough, coughing up blood, chest pain, and shortness of breath.
A new cough in a smoker or a former smoker should raise concern for lung cancer.
A cough that does not go away or gets worse over time should be evaluated by a healthcare professional.
Coughing up blood (hemoptysis) occurs in a significant number of people who have lung cancer. Any amount of coughed-up blood is cause for concern.
Chest pain is a symptom in about one-fourth of people with lung cancer. The pain is dull, aching, and persistent.
Shortness of breath usually results from a blockage to the flow of air in part of the lung, collection of fluid around the lung (pleural effusion), or the spread of tumor throughout the lungs.
Wheezing or hoarseness may signal blockage or inflammation in the lungs that may go along with cancer.
Repeated respiratory infections, such as bronchitis or pneumonia, can be a sign of lung cancer.
Symptoms of metastatic lung tumors depend on the location and size. About 30% to 40% of people with lung cancer have some symptoms or signs of metastatic disease.
Lung cancer most often spreads to the liver, the adrenal glands, the bones, and the brain.
Metastatic lung cancer in the liver may cause a loss of appetite, feeling full early on while eating, and otherwise unexplained weight loss.
Metastatic lung cancer in the adrenal glands also typically causes no symptoms.
Metastasis to the bones is most common with small cell cancers but also occurs with other lung cancer types. Lung cancer that has metastasized to the bone causes bone pain, usually in the backbone (vertebrae), the large bones of the thigh (the femurs), the pelvic bones, and the ribs.
Lung cancer that spreads to the brain can cause difficulties with vision, weakness on one side of the body, and/or seizures.
Paraneoplastic syndromes are the remote, indirect effects of cancer not related to direct invasion of an organ by tumor cells. Often they are caused by chemicals released from the cancers.
Symptoms
Symptoms include the following:
Clubbing of fingers -- the depositing of extra tissue under the fingernails
New bone formation -- along the lower legs or arms
Increased risk of blood clots in the arms, legs, or lungs
Low sodium levels
High calcium levels
Low potassium levels
Degenerative conditions of the nervous system otherwise unexplained.
Diagnosis
Upon hearing about the symptoms, a health care provider will formulate a list of possible diagnoses. The doctor will ask questions about the symptoms, medical and surgical history, smoking and work history, and other questions about lifestyle, overall health, and medications.
Unless severe hemoptysis is occurring, a chest X-ray will most likely be performed first to look for a cause of the respiratory symptoms.
The X-ray may or may not show an abnormality.
Types of abnormalities seen in lung cancer include a small nodule or nodules or a large mass.
Not all abnormalities observed on a chest X-ray are cancers. For example, some people develop scarring and calcium deposits in their lungs that may look like tumors on a chest X-ray.
In most cases, a CT scan or MRI of the chest will further define the problem.
If symptoms are severe, the X-ray may be skipped and a CT scan or MRI may be performed right away.
The advantages of CT scan and MRI are that they show much greater detail than X-rays and are able to show the lungs in three dimensions.
These tests help determine the stage of the cancer by showing the size of the tumor or tumors.
They can also help identify spread of the cancer into nearby lymph nodes or certain other organs.
If a person's chest X-ray or scan suggests that a tumor is present, he or she will undergo a procedure for diagnosis. Diagnosis requires analysis of cells or tissue sufficient to make the cancer diagnosis with certainty.
This procedure involves collection of sputum, removal of a small piece of the tumor tissue (biopsy) or a small volume of fluid from the sac around the lung.
The retrieved cells are reviewed under a microscope by a doctor who specializes in diagnosing diseases by looking at cell and tissue types (a pathologist).
Several different ways exist to obtain these cells.
Sputum testing: This is a simple test that is sometimes performed to detect cancer in the lungs.
Sputum is thick mucus that may be produced during a cough.
Cells in the sputum can be examined to see if they are cancerous. This is called cytology testing.
This is not a completely reliable test. If negative, the findings usually need to be confirmed by further testing.
Bronchoscopy: This is an endoscopic test, meaning that a thin, flexible, lighted tube with a tiny camera on the end is used to view organs inside the body.
Bronchoscopy is endoscopy of the lungs. The bronchoscope is inserted through the mouth or nose and down the windpipe. From there, the tube can be inserted into the airways (bronchi) of the lungs.
A tiny camera transmits images back to a video monitor.
The physician operating the bronchoscope can look for tumors and collect samples of any suspected tumors.
Bronchoscopy can usually be used to determine the extent of the tumor.
The procedure is uncomfortable. A local anesthetic is administered to the mouth and throat as well as sedation to make bronchoscopy tolerable.
Bronchoscopy has some risks and requires a specialist proficient in performing the procedure.
Cancer of the lung, 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 known as a tumor.
Tumors can be benign or malignant; when we speak of "cancer," we are referring to those tumors that are malignant. Benign tumors usually can be removed and do not spread to other parts of the body. Malignant tumors, on the other hand, often grow aggressively locally where they start, but tumor cells also can enter into the bloodstream or lymphatic system and then spread to other sites in the body. This process of spread is termed metastasis; the 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 very life-threatening cancer and one of the most difficult cancers to treat. While lung cancer can spread to any organ in the body, certain locations -- particularly the adrenal glands, liver, brain, and bones -- are the most common sites for lung cancer metastasis.
The lung also is a very common site for metastasis from malignant tumors in other parts of the body. Tumor metastases are made up of the same types of cells as the original (primary) tumor. For example, if prostate cancer spreads via the bloodstream to the lungs, it is the metastatic prostate cancer in the lung and is not lung cancer.
The principal function of the lungs is to exchange gases between the air we breathe and the blood. Through the lung, carbon dioxide is removed from the bloodstream and oxygen enters the bloodstream. The right lung has three lobes, while the left lung is divided into two lobes and a small structure called the lingula that is the equivalent of the middle lobe on the right. The major airways entering the lungs are the bronchi, which arise from the trachea, which is outside of the lungs. The bronchi branch into progressively smaller airways called bronchioles that end in tiny sacs known as alveoli where gas exchange occurs. 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%-95% of cancers of the lung is thought to arise from the 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 carcinomas. (Carcinoma is another term for cancer.) Cancers also can arise from the pleura (called mesotheliomas) or rarely from supporting tissues within the lungs, for example, the blood vessels.
Causes and Risk factors for Lung Cancer
Smoking
The incidence of lung cancer is strongly correlated with cigarette smoking, with about 90% of lung cancers arising as a result of tobacco use. The risk of lung cancer increases with the number of cigarettes smoked and the time over which smoking has occurred; doctors refer to this risk in terms of pack-years of smoking history (the 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 20 pack-year smoking history. While the risk of lung cancer is increased with even a 10-pack-year smoking history, those with 30-pack-year histories or more are considered to have the greatest risk for the development of 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 also can cause lung cancer, although the risk is not as high as with cigarette smoking. Thus, while someone who smokes one pack of cigarettes per day has a risk for the development of lung cancer that is 25 times higher than a nonsmoker, pipe, and cigar smokers have a risk of lung cancer that is about five times that of a nonsmoker.
Tobacco smoke contains over 4,000 chemical compounds, many of which have been shown to be cancer-causing or carcinogenic. The two primary carcinogens in tobacco 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 cessation of smoking.
Passive smoking
Passive smoking or the inhalation of tobacco smoke by nonsmokers who share living or working quarters with smokers also is an established risk factor for the development of lung cancer. Research has shown that nonsmokers who reside with a smoker have a 24% increase in risk for developing lung cancer when compared with nonsmokers who do not reside with a smoker. The risk appears to increase with the degree of exposure (number of years exposed and number of cigarettes smoked by the household partner). It is estimated that over 7,000 lung cancer deaths occur each year in the U.S. that are attributable to passive smoking.
Symptoms and Signs
Up to one-fourth of all people with lung cancer may have no symptoms when the cancer is diagnosed. These cancers usually are identified incidentally when a chest X-ray is performed for another reason. The majority of people, however, develop symptoms. The symptoms are due to direct effects of the primary tumor, to effects of metastatic tumors in other parts of the body, or to disturbances of hormones, blood, or other systems caused by cancer.Symptoms of primary lung cancers include a cough, coughing up blood, chest pain, and shortness of breath.
A new cough in a smoker or a former smoker should raise concern for lung cancer.
A cough that does not go away or gets worse over time should be evaluated by a healthcare professional.
Coughing up blood (hemoptysis) occurs in a significant number of people who have lung cancer. Any amount of coughed-up blood is cause for concern.
Chest pain is a symptom in about one-fourth of people with lung cancer. The pain is dull, aching, and persistent.
Shortness of breath usually results from a blockage to the flow of air in part of the lung, collection of fluid around the lung (pleural effusion), or the spread of tumor throughout the lungs.
Wheezing or hoarseness may signal blockage or inflammation in the lungs that may go along with cancer.
Repeated respiratory infections, such as bronchitis or pneumonia, can be a sign of lung cancer.
Symptoms of metastatic lung tumors depend on the location and size. About 30% to 40% of people with lung cancer have some symptoms or signs of metastatic disease.
Lung cancer most often spreads to the liver, the adrenal glands, the bones, and the brain.
Metastatic lung cancer in the liver may cause a loss of appetite, feeling full early on while eating, and otherwise unexplained weight loss.
Metastatic lung cancer in the adrenal glands also typically causes no symptoms.
Metastasis to the bones is most common with small cell cancers but also occurs with other lung cancer types. Lung cancer that has metastasized to the bone causes bone pain, usually in the backbone (vertebrae), the large bones of the thigh (the femurs), the pelvic bones, and the ribs.
Lung cancer that spreads to the brain can cause difficulties with vision, weakness on one side of the body, and/or seizures.
Paraneoplastic syndromes are the remote, indirect effects of cancer not related to direct invasion of an organ by tumor cells. Often they are caused by chemicals released from the cancers.
Symptoms
Symptoms include the following:
Clubbing of fingers -- the depositing of extra tissue under the fingernails
New bone formation -- along the lower legs or arms
Increased risk of blood clots in the arms, legs, or lungs
Low sodium levels
High calcium levels
Low potassium levels
Degenerative conditions of the nervous system otherwise unexplained.
Diagnosis
Upon hearing about the symptoms, a health care provider will formulate a list of possible diagnoses. The doctor will ask questions about the symptoms, medical and surgical history, smoking and work history, and other questions about lifestyle, overall health, and medications.
Unless severe hemoptysis is occurring, a chest X-ray will most likely be performed first to look for a cause of the respiratory symptoms.
The X-ray may or may not show an abnormality.
Types of abnormalities seen in lung cancer include a small nodule or nodules or a large mass.
Not all abnormalities observed on a chest X-ray are cancers. For example, some people develop scarring and calcium deposits in their lungs that may look like tumors on a chest X-ray.
In most cases, a CT scan or MRI of the chest will further define the problem.
If symptoms are severe, the X-ray may be skipped and a CT scan or MRI may be performed right away.
The advantages of CT scan and MRI are that they show much greater detail than X-rays and are able to show the lungs in three dimensions.
These tests help determine the stage of the cancer by showing the size of the tumor or tumors.
They can also help identify spread of the cancer into nearby lymph nodes or certain other organs.
If a person's chest X-ray or scan suggests that a tumor is present, he or she will undergo a procedure for diagnosis. Diagnosis requires analysis of cells or tissue sufficient to make the cancer diagnosis with certainty.
This procedure involves collection of sputum, removal of a small piece of the tumor tissue (biopsy) or a small volume of fluid from the sac around the lung.
The retrieved cells are reviewed under a microscope by a doctor who specializes in diagnosing diseases by looking at cell and tissue types (a pathologist).
Several different ways exist to obtain these cells.
Sputum testing: This is a simple test that is sometimes performed to detect cancer in the lungs.
Sputum is thick mucus that may be produced during a cough.
Cells in the sputum can be examined to see if they are cancerous. This is called cytology testing.
This is not a completely reliable test. If negative, the findings usually need to be confirmed by further testing.
Bronchoscopy: This is an endoscopic test, meaning that a thin, flexible, lighted tube with a tiny camera on the end is used to view organs inside the body.
Bronchoscopy is endoscopy of the lungs. The bronchoscope is inserted through the mouth or nose and down the windpipe. From there, the tube can be inserted into the airways (bronchi) of the lungs.
A tiny camera transmits images back to a video monitor.
The physician operating the bronchoscope can look for tumors and collect samples of any suspected tumors.
Bronchoscopy can usually be used to determine the extent of the tumor.
The procedure is uncomfortable. A local anesthetic is administered to the mouth and throat as well as sedation to make bronchoscopy tolerable.
Bronchoscopy has some risks and requires a specialist proficient in performing the procedure.
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