Risk Factors

Lung cancer cannot be passed from one person to another like the flu or a cold. You cannot get lung cancer by touching a person with lung cancer or by being exposed to their bodily fluids. Scientists are learning more about the things that cause lung cancer and what can be done to prevent it. Of all lung cancer cases, 85% or more occur among people who have a history of smoking tobacco. Scientists have also recently shown that smoking marijuana and crack-cocaine also increases the risk for developing lung cancer. Nevertheless, about one out of every 6 people who develop lung cancer has never smoked.

Exposure to certain chemicals, such as those found in cigarette smoke, can increase a person’s risk of lung cancer. Scientists know that genes, or a genetic predisposition, can increase the risk of developing lung cancer. It is also known that, sometimes, people develop lung cancer for no specific reason that can be identified.

Smoking

Smoking is the most common cause of lung cancer. For smokers, the risk of developing lung cancer is related to their total lifetime exposure to cigarette smoke and is measured by the number of cigarettes smoked per day, the age at which smoking began, and the number of years a person has smoked. Because most lung cancers are present for several years before they become symptomatic, the risk for lung cancer does not begin to decline until several years after smoking cessation. However, 10 years after quitting, the risk of lung cancer in former smokers is about 20% to 50% of those who continue to smoke. The risk continues to decline gradually the more time a person has stopped smoking. However, a former smoker’s risk of lung cancer never returns to that of someone who has never smoked. A former smoker’s risk remains higher than that of someone who has never smoked.

Why Should I Quit Smoking?

The good news is that quitting can reduce a smoker’s risk of developing lung cancer. It is still highly advantageous and advisable for a smoker to quit, no matter how long he or she has smoked. For example, former smokers who are diagnosed with lung cancer generally do better with surgery and treatment than do active smokers. In addition, when smokers quit, they slow the progress of other lung disorders such as chronic obstructive pulmonary disease (COPD) and emphysema. Smokers who quit also reduce their risk of heart disease by 2 years compared to that of nonsmokers and reduce their risk for developing other cancers for which smoking may also be a risk factor.

What About Second-Hand Smoke?

The health risks of tobacco smoke are not limited to smokers. Exposure to other people’s smoke, called “second-hand smoke,” “side-stream smoke,” or “environmental tobacco smoke,” also increases a person’s risk of lung cancer. The Environmental Protection Agency estimates that every year, 3,000 people in the United States die of lung cancer caused by second-hand smoke. Living with a smoker can increase a person’s risk of lung cancer. Likewise, any job that exposes a person to environmental smoke, such as working in a bar or some restaurants, being a flight attendant on an international airline, or working in an office where smoking is allowed, can increase a person’s risk of lung cancer.

Age and Gender

Age itself may increase a person’s risk of lung cancer. As we age, some of our cells may become damaged so that they do not divide normally, which can lead to cancer. In addition, our immune system does not work as well as we age, so that cancer cells have a greater chance of slipping through our body’s natural surveillance system undetected. Also, as we live longer, the more chance of exposure we have to other carcinogens. Therefore, historically, lung cancer has tended to occur in older people, predominately those between 50 and 70 years.

New studies indicate that females who smoke may be more sensitive than males to carcinogens such as tobacco. Young people, especially women, are currently developing lung cancer at alarming rates. This increase will continue as long as people start smoking at young ages.

Genetics

Our genes can affect our risk of getting lung cancer. In fact, cancer is now considered to be a disease caused by damaged genes. One of the most striking features of lung cancer is the large number of genetic changes or mutations, often 10 to 20, found in lung cancer cells.

People whose parents or siblings have or had lung cancer may have a genetic predisposition to and a greater risk of developing lung cancer. Other people are born with genes that are resistant and they may be less susceptible to getting any kind of cancer. More is being learned through research about the role of genes and genetic mutations in the development of lung cancer and other types of cancer.

Asbestos

People exposed to asbestos have an increased risk of a rare form of cancer that occurs primarily in the lungs called malignant mesothelioma. Though smoking does not appear to be a risk factor for malignant mesothelioma, asbestos workers who smoke have an increased risk of developing lung cancer. Studies have shown that asbestos workers who smoke may have a 5-fold increased risk of getting lung cancer than nonsmokers exposed to asbestos. In this case, smoking and exposure to asbestos can multiply the risk of getting lung cancer.

Other Environmental Factors

Exposure to radon, a naturally occurring, colorless, odorless gas that seeps out of the earth’s crust, possibly increases the risk of lung cancer. Underground miners may be at an increased risk for lung cancer if uranium is present in the mines where they work. Some people live in areas that have naturally occurring high levels of radon.

Exposure to other chemicals including arsenic, bis-chloromethyl ether (BCME), chromium and chromium compounds, nickel and nickel compounds, polycyclic aromatic hydrocarbons (PAH), and vinyl chloride are known to increase the risk of lung cancer. These chemicals are most likely encountered in certain work settings.

Symptoms of Lung Cancer

Many people do not have symptoms, or have only vague symptoms, until the disease has progressed significantly. As a result, only 15% of lung cancers are discovered in early stages when the possibility of curative treatment is greatest.

When lung cancer does cause symptoms, they can include:

•  Coughing
•  Shortness of breath (dyspnea)
•  Fatigue
•  Chest, shoulder, upper back, or arm pain
•  Repeated pneumonia or bronchitis
•  Blood coughed up in sputum (hemoptysis)
•  Loss of appetite and weight loss
•  General pain
•  Hoarseness
•  Wheezing
•  Swelling in the face or neck

Sometimes, symptoms may seem unrelated to the lungs or breathing. Because lung cancer is most likely to be diagnosed in a later stage, the primary cancer may have already spread to the other lung or other parts of the body. Depending upon where the cancer spreads and which organs are affected, symptoms can also include headaches, bleeding, weakness, bone fractures, or blood clots.

Screening for Lung Cancer

Screening programs are designed to identify and follow high-risk patients in order to detect disease as early as possible. While there are no officially recommended screening programs for lung cancer at this time, people who think that they may be at risk for lung cancer because of smoking history, occupation, or family health history should inform their health care provider and discuss appropriate diagnostic testing.

Routine chest x-rays have generally not been found to be beneficial in the early detection of lung cancer. Currently, a specialized x-ray test called a spiral CT scan shows promise in aiding early detection efforts.

A CT scan can detect a tumor much earlier than it can be seen on a chest x-ray. New sputum cytology tests are also in development. In these tests, sputum or fluid from the lungs will be examined to determine whether any cancer cells are present.

It is thought that some people have a genetic susceptibility to cancer. Research studies are being done with the hope that it may be possible in the near future to screen for a genetic predisposition to lung cancer so that those who are at greater risk could be more closely monitored.

Much work has yet to be done to develop a widely accepted, valid, cost-effective, early-detection program for lung cancer. Early detection is the key to improving survival following a diagnosis of lung cancer. In late 2001, the National Cancer Institute approved a lung cancer screening trial that will test whether spiral CT screening can detect lung cancers early enough to reduce mortality. The study will examine 50,000 former smokers between the ages of 55-74 over the next 8 years. For more information on this study and screening centers, contact the NCI at 1-800-4CANCER.

Diagnostic and Staging Methods

The diagnosis and staging of lung cancer is a multi-step process that is required so that you and your health care providers are able to make decisions about what type of treatment you will need. The following is a list of the typical diagnostic tests used to determine not only a diagnosis of lung cancer but the stage of the disease as well.

Health History

One of the most important steps a physician takes in diagnosing lung cancer is obtaining a health history. Smoking history is an important part of the health history as is any history of exposure to asbestos and other environmental factors. Your health history will tell your physician about any significant symptoms you may be experiencing, such as nagging cough, shortness of breath, fatigue, or back or chest pain. Your family health history will also be considered. For instance, your physician will most likely inquire about cancer in close relatives, which may indicate a genetic predisposition to lung cancer.

Physical Exam

During the physical exam, your doctor will listen to your lungs and the sounds of your breathing. In addition, he or she may request special breathing tests or pulmonary function tests to determine if your breathing is impaired. He or she will also check for swollen lymph nodes in the neck or in the region above the collarbones and will feel the liver to see if it is enlarged or if any masses are present in the abdomen.

Diagnostic Tests

One or more the following diagnostic tests may be ordered:

Chest X-ray

A chest x-ray is usually the first test done to detect lung cancer. It is a type of picture that can help locate a tumor. If symptoms are present at the time a chest x-ray is done, the cancer may have already spread into the lymph nodes or to other parts of the body. Nonetheless, 50% of stage I lung cancers that are detected by chest x-ray do not have symptoms present. Among such patients, the 5-year survival ranges from 60% to 85%. A chest x-ray may not show a tumor, possibly because it is too small or it may be hidden behind a rib or the breastbone. But an x-ray may show other clues that indicate a problem related to lung cancer. For example, an x-ray may show an accumulation of fluid between the lung and the chest wall called a pleural effusion. An x-ray may also show enlarged lymph nodes or pneumonia.

Even if the diagnosis of lung cancer is already clear, your doctor may want to take an x-ray to compare with previous and future x-rays. This will help chart the course of the disease and provide important information about changes that occur during treatment.

CT and MRI Scans

CT (computerized axial tomography) and MRI (magnetic resonance imaging) scans use computers to produce highly detailed cross-sectional (slices) images of the body. They can show 3-dimensional images that help determine the size, shape, and location of a tumor.

If you or your health care providers believe you might have symptoms of lung cancer, the best diagnostic test to use may well be the CT scan. The CT scan is usually less expensive than an MRI and in most instances is preferred because the MRI has little advantage, if any.

Both CT and MRI scans are useful in determining whether a tumor has spread from the lung to the lymph nodes or other parts of the body.

PET Scans

PET (Positron Emission Tomography) scanning is different from CT and MRI scanning because PET scans discriminate between cells that are rapidly dividing, such as tumor cells. While PET scans are used as a screening or even a diagnostic test for lung cancer, they can also be used as a follow-up to chest x-rays, CT scans, or MRI scans to determine if a tumor is cancerous and determine the presence and location of metastatic disease.

Sputum Cytology

If there are cancer cells in the bronchi, some of these cells are likely to be shed and carried up the throat in the sputum, which is mucus from the airways. Sputum cytology is the examination of a sample of sputum under a microscope for signs of cancer cells. Sputum may be collected by coughing up fluid from the lungs into a collection cup. Or sputum may be collected through the use of a bronchoscope, a tube inserted into the throat and down into the lungs, which can obtain fluid or sputum from the lungs.

A bronchoscopic examination of the sputum can detect early cancer because cancer cells can be found in the sputum long before a tumor is evident on an x-ray, CT, or MRI scan. However, sputum cytology may not always detect the presence of cancers that are located deeper in the lungs. Also, sputum cytology cannot determine the size or location of a tumor, so it is usually followed up by other tests if the results are positive. New products may soon be available that can help doctors get a better sputum sample, even from those hard-to-reach areas of the lungs.

Genetic Markers

Researchers are working to identify genetic markers, or “fingerprints,” that indicate the presence of tumors. Markers are detected in blood samples using special laboratory tests. These tests are not routinely run at present. Studies in lung cancer are currently underway. Hopefully, the identification of markers may someday allow for earlier detection of lung cancer.

Follow-up Tests

If a suspicious area is seen in any of the scans or an x-ray, or if suspicious cells are found in the sputum, your doctor will request that more tests be done.

Biopsy

A biopsy involves obtaining a small piece of tissue and examining it under a microscope. A biopsy is necessary to confirm a cancer diagnosis and to identify the specific type of cancer and its stage. In some cases, a needle is used to aspirate a sample to be examined for cancer cells. A CT scan is usually done prior to a needle aspiration to locate the tumor to be tested. Sometimes, surgical biopsies of the lung may be performed. If a surgical biopsy is needed, the surgeon will perform the surgery through an incision in the chest so that all or part of a tumor or lymph nodes can be removed. In addition, biopsies of the chest lining, lymph nodes, bone, or liver may be performed. No matter how or from where a sample of tissue is obtained, a pathologist must ascertain if cancer is present, and, if so, identify its type. Only by examination of the cells can the diagnosis of lung cancer be made.

Bronchoscopy

Bronchoscopy involves the use of a bronchoscope to directly view the airways into the lungs. A bronchoscope is a tube-like instrument that can be inserted through your air passages to allow your doctor to see parts of your lungs and also to collect specimens. The fiber optic, flexible bronchoscope allows it to go around corners. Local anesthesia and mild sedation are generally used to make the patient comfortable during the procedure.

A relatively new technique known as auto-fluorescence bronchoscopy allows physicians to observe whether cells fluoresce (reflect light) normally. A fluorescent dye is injected into and taken up by the tumor cells that cause them to fluoresce. If the cells do not fluoresce normally, a sample is taken to determine whether they are cancerous. This technique is used in special circumstances when ordinary bronchoscopy fails to reveal a tumor detected by sputum cytology.

Mediastinoscopy

Mediastinoscopy involves inserting a rigid endoscope through a small incision in the neck or chest into the mediastinum. The procedure is done while the patient is under anesthesia. The purpose of this procedure is to determine whether cancer has spread to the chain of lymph nodes near the trachea, one of the first places lung cancer is likely to spread.

Thoracentesis

If there is fluid collecting between the lungs and the chest wall, a needle can be inserted to extract fluid to see if it contains cancerous cells.

Thoracoscopy

Thoracoscopy is a limited surgical procedure that allows the lining of the chest wall and the surface of the lungs to be examined for tumor growth. The procedure is performed in an operating room while the patient is under general anesthesia. In the procedure, the thoracoscope is inserted through a small incision in the chest wall.

The newest technique is called video-assisted thoracoscopic surgery (VATS). When this procedure is used, a second small incision is made to allow the insertion of a small video camera. The camera aids the surgeon in scanning the chest wall and lungs, allowing suspicious pieces of tissue to be removed.

For some people, the next steps will include a surgical procedure. This is usually done when the physician believes there is a significant chance that cancer is present and that the tumor or tumors can be successfully removed.

Thoracotomy

Thoracotomy is a major operation during which the surgeon makes an incision into the chest so that he/she can examine the lungs. This surgery is usually done only when the surgeon is quite sure that lung cancer is present and that excision (surgical removal) could provide a cure. If a tumor is found, it is biopsied or removed during surgery. If necessary, frozen sections of tissue examined by the pathologist can confirm diagnosis, including the histological type of lung cancer. The margins, or edges, of the resection can also be examined for tumor fragments. If the pathologist’s report indicates that the tumor type should and can be removed, part of the lung or the entire lung may be removed. In this case, both diagnosis and treatment are carried out at the same time.