A Guide to Diagnosis and Treatment
By Walter J. Scott, Jack Kusler
Addicus Books, Inc. Copyright © 2012 Walter J. Scott, M.D.
All rights reserved.
Lung Cancer: An Overview
Hasn't it seemed that cancer was always something that happened to someone else? But now, you or perhaps a loved one has been diagnosed with lung cancer. Your initial reaction may have been shock or that feeling of dread that comes with having your worst fears confirmed. You may feel sad, confused, and scared. These are normal reactions.
After receiving the initial diagnosis, you may have wondered what happens next? What medical tests will you undergo? What treatment will you need? Hopefully, the chapters that lie ahead will answer many of your questions. To start, however, this first chapter will give you a basic understanding of lung cancer.
How Lung Cancer Develops
Cancer is a collection of cells growing out of control. The cells in our bodies are constantly growing, and each cell contains a set of instructions, like software in a computer, that regulate cell behavior. Sometimes, a change, or mutation, occurs in a cell's growth pattern. When these mutations continue to occur — as many as ten to twenty may be required — the once-normal cells begin to grow abnormally. These new growths are called cancers.
Lung cancer usually arises from the cells that line the airways and the nearby mucous glands. When the airways are exposed to toxins we inhale, the transformation of normal cells to cancer begins with a condition called hyperplasia — an increase in the number of cells lining one part of the airways through which we breathe. This is followed by the development of dysplasia, which is an increase in the number of abnormal cells that line the airways. From this point, malignant cells can emerge. If left untreated, these cells can continue to grow and invade surrounding tissues.
How Lung Cancer Spreads
There are three ways cancer can spread: into surrounding tissues from the original tumor, through the blood, or through lymph nodes. The lymph nodes are part of the body's immune system — they filter the blood for foreign particles, such as bacteria or cancer cells. There are hundreds of lymph nodes throughout your body. Normally, when not inflamed or cancerous, lymph nodes are the size of raisins. Lung cancer can spread to lymph nodes in the chest.
In addition to spreading to lymph nodes, the malignant cells can escape into the bloodstream and travel throughout the body. Lung cancer most commonly spreads to the liver, but can also spread to the bones, bone marrow, brain, and adrenal glands. When a secondary cancer forms in any of these organs, it is called a metastasis.
Types of Lung Cancer
There are more than a dozen types of lung cancer, but more than about 90 percent of them fall into two main categories: non-small cell lung cancer and small cell lung cancer. These two forms of lung cancer grow differently and are also treated differently. Whether the cancer is non-small cell or small cell is determined by the size and other characteristics of the cancer cells as they appear when viewed through a microscope.
Non-Small Cell Lung Cancer
Approximately 80 percent of all lung cancers fall into the category of non-small cell lung cancer. It's called non-small cell because when viewed through a microscope, the cells appear large — or non-small. There are two main forms of non-small cell lung cancer: adenocarcinoma and squamous cell carcinoma.
Adenocarcinomas are usually found in the outer edges of the lung and arise from the tiny glands that produce mucus in the smaller airways (called alveoli). This is the most common form of non-small cell lung cancer.
Squamous cell carcinomas generally arise in the bronchial tubes in the center of the chest. These cancers grow in the squamous cells in the bronchial lining.
Small Cell Lung Cancer
About 13 percent of all lung cancers are categorized as small cell lung cancer. This form of lung cancer often occurs in the lining of the major breathing tubes in the center of the chest. Small cell lung cancer tends to grow quickly. By the time it is diagnosed, it has often spread to the lymph nodes in the center of the chest and may even have spread through the bloodstream to other organs in the body.
Risk Factors for Lung Cancer
Most experts believe that more than 80 percent of all cancers occur in response to environmental factors. These factors include such things as cigarette smoke and toxic chemicals. Other risk factors include aging and heredity may also be factors.
Cigarette smoke contains some four thousand chemicals, and at least fifty of them are known carcinogens (cancer-producing substances). Although fewer than 20 percent of smokers will develop lung cancer, scientists have determined that the chemicals in cigarette smoke cause more than 80 to 90 percent of all lung cancers. The risk of developing lung cancer increases significantly with ten to twenty years of regularly smoking one to two packs of cigarettes per day.
For smokers who do not develop lung cancer, smoking may still take a toll on their health in other ways. Many thousands will develop, and die prematurely from, illnesses such as emphysema, chronic obstructive pulmonary disease (COPD), heart disease, stroke, and accelerated hardening of the coronary arteries, which can lead to heart attacks.
Quitting smoking decreases a person's risk of developing lung cancer. Ten years after quitting, the risk drops by half. Smoking's harmful effects on the heart also decrease immediately with smoking cessation.
Before 1930, the U.S. government kept few statistics on lung cancer because the disease was so rarely seen. However, by 1986, it had long been the leading cause of cancer deaths in American men and had surpassed breast cancer as the leading cause of cancer deaths in American women. How did lung cancer become the most common cause of death from cancer in both sexes? The main cause is the rise in cigarette consumption.
If you live with or are frequently around smokers, passive smoking may be a risk factor for you. Nonsmokers who live with smokers are estimated to have a 24 percent higher risk of developing lung cancer compared to those who do not live with smokers. Passive smoking claims nearly three thousand lives annually in the United States.
Certain environmental factors are thought to increase the risk of developing lung cancer. The natural, odorless gas called radon is considered a carcinogen. Radon is believed to cause some twenty thousand lung cancer deaths annually in the United States, making it the second-leading cause of such deaths.
Radon is created by the radioactive decay of uranium and is found in soil and rocks. It may seep into homes and other buildings through pipes, drains, or cracks in foundations.
Asbestos, a fibrous mineral once commonly used in the construction of homes and other buildings, is considered the cause of a form of cancer known as mesothelioma. Asbestos fibers may break into particles and float into the environment. When inhaled, the particles may stick to the lungs and remain there for a lifetime. The long-term effects of exposure to asbestos may not develop until twenty to thirty years after the exposure.
The risk of developing cancer from asbestos exposure is based on the amount and duration of the exposure. People who have worked around asbestos have a five times greater risk of developing lung cancer compared to those who have never worked around asbestos. People who have been exposed to asbestos and who have also been smokers have a risk fifty to ninety times greater than that of nonsmokers. In the 1970s, the U.S. government began banning the use of asbestos in the construction of homes and other buildings.
Other chemicals that increase the risk of lung cancer include vinyl chloride, an odorless gas used in the making of plastics and vinyl, and chromium, a metallic element used in chrome plating and stainless steel welding. Also associated with an increased risk of lung cancer is exposure to nickel refinery dust and fumes; nickel is used in the making of metals — most notably, stainless steel. Finally, exposure to arsenic may cause lung cancer; arsenic is found in pesticides and is used in the production of many products, including glass, enamel, and textiles.
Increasing age lowers a person's defenses against virtually all diseases, including lung cancer. Nearly 70 percent of those diagnosed with lung cancer are over the age of sixty-five. Only about 3 percent of cases are diagnosed in people younger than forty-five.
Also, as we age we are more susceptible to the actions of free radicals, organic molecules that are responsible for aging, tissue damage, and possibly some diseases.
Genetics do not appear to be a major risk factor in who develops lung cancer. However, research has shown that genes may play a role in some families. It is believed that some individuals may not be able to rid their bodies of certain cancer-causing agents, leaving them more vulnerable to cancer. Others may have faulty repair mechanisms in their cells, also leaving them at higher risk for cancer.
Lung cancer is the second most common cancer among both men and women in the United States. Approximately 220,000 thousand Americans are diagnosed with lung cancer annually. The disease accounts for 15 percent of all new cancers and causes more deaths than cancers of the colon, prostate, and breast combined.
The key to surviving lung cancer is early detection. However, symptoms of lung cancer are not always noticeable, especially if the cancer is in at an early stage. The next chapter will discuss the symptoms of lung cancer.
Symptoms of Lung Cancer
The symptoms of lung cancer can be elusive. In fact, about 25 percent of lung cancer patients have no symptoms at all at the time of diagnosis; their cancer is caught during routine X-rays or scans, often to the surprise of both the patient and the doctor. In many cases, symptoms of lung cancer are not noticeable until the cancer has progressed.
If a person has symptoms that may be associated with lung cancer, his or her physician will consider the symptoms in relation to the person's history. For example, a doctor would not immediately suspect lung cancer in a twenty-five-year-old woman who has persistent coughing and wheezing. On the other hand, a diagnosis of lung cancer would be more likely in a sixty-five-year-old woman who has smoked two packs of cigarettes for thirty years and has the same symptoms.
It's important to seek medical attention when you have any of the symptoms of lung cancer. The sooner symptoms are reported, the sooner the problem, if any, can be diagnosed and treated.
As noted in chapter 1, lung cancer usually arises from the cells lining the airways. The nerves lining the airways detect the presence of anything foreign — dust, dirt, blood, or a tumor. These nerves stimulate the cough reflex, designed to help the body rid itself of foreign particles and keep the airways clean. If a tumor develops in the large airways, coughing may be a prominent symptom. People with lung cancer who never complain of a cough probably have a tumor located away from the center of the lung, in the smaller airways, where there are few cough receptors.
Blood in the Sputum
Sputum refers to mucus coughed up from the lungs. If the surface of a tumor bleeds, the patient may cough up blood-tinged mucus. This serious symptom, called hemoptysis, should be evaluated immediately.
When breathing passages are blocked completely by a tumor, infection may occur in the blocked or obstructed area. This leads to fever and coughing up dark sputum. It is important not to confuse this condition with pneumonia, which produces similar symptoms but responds to antibiotic treatment.
A tumor may result in wheezing, the sound produced when air tries to pass through a partially blocked airway in the lung. A tumor will produce localized wheezing, best heard on the side of the chest where the tumor is located.
The surface lining of the lungs and the inside lining of the chest cavity, known as the pleura, have many nerve fibers. Therefore, a cancer that irritates the surface linings of the lung or the chest wall can cause chest pain. The pain usually occurs where the cancer is irritating the pleura. It may be constant, or it may come and go with breathing. This pain is called pleuritic chest pain. It suggests that the cancer may be growing on the surface of the lung and even into the chest wall. If the cancer has invaded the surface of the lung or the chest wall, it is more advanced. However, sometimes the cancer may irritate the surface of the lung without actually growing into it. Often, surgery is the only way to find out exactly how far the cancer has spread.
Because lung tissue itself has no nerves that sense pain, cancer may grow to a large size within the lung without causing pain. This is one reason why lung cancer is difficult to diagnose in its early stages.
The laryngeal nerves supply motor function to the vocal cords, allowing them to move, giving a person his or her normal voice. These nerves start in the brain, travel down into the chest, and then go back up into the neck to supply the voice box and vocal cords. Lung cancer may grow into one of these nerves where it passes through the chest. If this happens, the vocal cord controlled by the nerve becomes weakened or even paralyzed, and the person becomes hoarse. Persistent hoarseness or a change in the quality of a person's voice needs to be evaluated. A chest X-ray should be obtained as part of this evaluation.
If the cancer involves the sympathetic nerves, one of the eyelids may droop slightly or take longer to open than the other (lid lag). The sympathetic nerves, which control involuntary actions such as breathing, run in a chain along either side of the spine. These nerves are most vulnerable to damage from cancer arising in the top of the lung. Because the chest cavity narrows in this area, a cancer growing there may easily compress and grow into the surrounding structures.
In this case, a person may also have trouble seeing because one pupil is constricted (miosis), or he or she may notice that one side of the face is drier or less sweaty (anhidrosis). A combination of these symptoms is called Horner's syndrome.
Pain in the Arm and Armpit
Constant pain in the arm and armpit, typically accompanied by other symptoms, is known as Pancoast syndrome. The nerves that supply the arm and armpit come from the neck and travel over the top of the lung. A cancer in the top of the lung may compress these nerves, causing severe pain in the arm and armpit.
Shortness of Breath
Shortness of breath is a common symptom among people with lung cancer. Lung cancer can cause shortness of breath in several ways. A tumor that arises in a major airway and blocks the passage of air into an entire lung may cause shortness of breath. Lung cancer can also cause a buildup of fluid around the outside of the lung; this fluid buildup, called a pleural effusion, may prevent the lung from fully expanding, causing shortness of breath. Lung cancer may even affect the sac around the heart, known as the pericardium; it can cause fluid to build up within the sac, preventing the heart from working properly and resulting in shortness of breath.
Shortness of breath can also be caused by damage to the nerves in the diaphragm, a muscle important to breathing. If lung cancer involves one of these nerves, the half of the diaphragm that it controls becomes paralyzed. Movement of air in and out of the chest decreases, causing shortness of breath.
Swelling of the Face and Arms
Cancer arising in the right lung may compress the superior vena cava, the great vein that drains the blood from the head and arms and delivers it back to the heart and lungs. This compression can result in swelling of the face and arms, which is known as superior vena cava syndrome. This may prove serious if swelling in the neck and trachea interferes with breathing. (Continues...)
Excerpted from Lung Cancer by Walter J. Scott, Jack Kusler. Copyright © 2012 Walter J. Scott, M.D.. Excerpted by permission of Addicus Books, Inc..
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