Lung cancer

Lung cancer
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Last Updated: 11/10/2005
Introduction

Lung cancer is the leading cause of cancer deaths in the United States, among both men and women. It claims more lives than colon, prostate, lymph and breast cancer combined.

Yet most of these lung cancer deaths could have been prevented. That's because smoking accounts for nearly 90 percent of lung cancer cases. Although your risk of lung cancer increases with the length of time and number of cigarettes you smoke, quitting smoking, even after many years, can significantly reduce your chances of developing the disease. Protecting yourself from exposure to other leading causes of lung cancer, such as asbestos, radon and secondhand smoke, also decreases your risk.

Prevention is critical because lung cancer usually isn't discovered until it's at an advanced stage when the outlook for recovery is poor. Although the survival rates for lung cancer have improved, they remain much lower than those of many other types of cancer.


Signs and symptoms

Because lung cancer doesn't cause signs or symptoms in its earliest stages, it's often advanced by the time it's diagnosed. When symptoms do occur, the most common warning sign is a cough, which occurs when a tumor irritates the lining of the airways or blocks the passage of air. In addition to a new cough, be alert for:

"Smoker's cough" that worsens
Coughing up blood, even a small amount
Chest pain
Shortness of breath
New onset of wheezing
Repeated bouts of pneumonia or bronchitis
Hoarseness that lasts more than two weeks
Lung cancer also may cause fatigue, loss of appetite and weight loss. If it has spread to other parts of your body (metastasized), you may have headaches or bone pain.


Causes

Your lungs are two large, spongy organs shaped something like an upside-down butterfly. One lung is located on each side of your chest. They're separated by the mediastinum — the tissues and organs of your midchest, which include your heart, esophagus and windpipe (trachea) as well as lymph nodes and major blood vessels such as the aorta. Each lung is divided into upper sections called lobes. Your left lung has two lobes, and your right lung, which is larger, has three lobes.

Every time you inhale, air is carried through the windpipe to your lungs in two major airways (bronchi). Inside your lungs, the bronchi subdivide over 15 times into a million smaller airways (bronchioles), which finally end in clusters of tiny air sacs called alveoli. Within the air sacs, oxygen is absorbed into your bloodstream and carbon dioxide — a waste product of metabolism — is released.

How cancer forms
The lining of the airways and windpipe is made up of rectangular-shaped surface cells (columnar epithelium) and glands that produce mucus and other fluids. In healthy lungs, these cells divide in a controlled and orderly way. But when a cell becomes cancerous, it can continue to reproduce even when new cells aren't needed.

Although it may take years for lung cancer to develop, changes in lung tissue can begin almost immediately after your lungs are exposed to the cancer-causing substances (carcinogens) in cigarette smoke. With repeated exposure, normal cells are increasingly damaged, and eventually some may become cancerous. Because of the way lung cancer cells behave and because these cells have easy access to a large number of blood and lymph vessels, cancerous cells may spread to other parts of your body before you ever experience symptoms.

Leading causes of lung cancer
Cigarette smoking is the main cause of lung cancer. Tobacco smoke contains more than 3,500 chemicals, at least 40 of which are known carcinogens. Cigarettes also contain more than 30 toxic metals, including nickel and cadmium, as well as radioactive compounds.

Other causes of lung cancer include exposure to secondhand smoke, to asbestos and other industrial carcinogens, and to high concentrations of radon — an odorless gas that's released into the air from the breakdown of uranium in the soil and water. Smokers exposed to asbestos and radon are more likely to develop cancer than are nonsmokers.

Lung cancer that begins in the lungs (primary lung cancer) is uncommon in nonsmokers, but cancer of the breast, colon, prostate, testicle, kidney, thyroid, bone or other organs may spread to the lungs. In that case, the cancer is still referred to by the name of the organ in which it originated, rather than being called lung cancer. There's no connection between smoking and the spread of cancer cells to the lungs from other parts of the body.

Types of lung cancer
Lung cancer is commonly divided into two types: small cell and non-small cell. Each grows and spreads in different ways and is treated differently. Small cell lung cancer spreads early in the course of the disease and occurs almost exclusively in smokers. Surgical removal usually isn't an option for this type of cancer; instead, it's best treated with chemotherapy and radiation. Even so, the five-year survival rate for small cell lung cancer is very low.

Non-small cell lung cancer, which is more common, accounts for more than 75 percent of lung cancers. If caught early when it's confined to a small area, it often can be removed surgically. There are four major categories of non-small cell lung cancer:

Squamous cell carcinoma. This cancer forms in cells lining your airways. It's the most common type of lung cancer in men.
Adenocarcinoma. This type of cancer usually begins in the mucous-producing cells of the lung. It's the most common type of lung cancer in women and in people who have never smoked or were exposed to secondhand smoke.
Large cell carcinoma. This type of cancer originates in the peripheral part of the lungs.
Bronchoaveolar carcinoma. This uncommon type of non-small cell lung cancer tends to grow more slowly than other forms of the disease. It occurs more often in smokers than in nonsmokers and tends to arise in more than one location at the same time.


The lungs are two spongy organs located in the chest. Cancer may begin in the lungs or spread to the lungs from other organs.

Risk factors

Smoking remains the greatest risk factor for lung cancer, accounting for as many as 9 out of every 10 cases of the disease. Your risk increases with the number of cigarettes you smoke each day and the number of years you have smoked. Your risk is also greater if you start smoking early in life — even if you later quit. Smoking filtered, low-tar or low-nicotine tobacco offers no additional protection because most people who smoke these cigarettes inhale more deeply, which also increases the risk.

On the other hand, quitting — at any age — can significantly lower your risk of developing lung cancer. After 10 years of not smoking, your risk of lung cancer is reduced by one-third. Cutting the number of cigarettes you smoke may also reduce your risk, though not as dramatically as quitting completely.

Other risk factors include:

Your sex. Current or former women smokers are at greater risk of lung cancer than are men who have smoked an equal amount. Although the exact reasons for this are unknown, some experts speculate that women may have a greater susceptibility to the cancer-causing substances found in tobacco. Others believe that estrogen may play a role. Women also are known to inhale more than men do, and they are less likely to quit.
Exposure to secondhand smoke. Even if you don't smoke yourself, you're at high risk of lung cancer if you're exposed to the smoke of others. Daily exposure to secondhand smoke may increase your chances of developing lung cancer.
Exposure to radon gas. Second only to smoking as a cause of lung cancer, radon comes from the natural (radioactive) breakdown of uranium in soil, rock and water that eventually becomes part of the air you breathe. Although unsafe levels of radon can accumulate in any building, the greatest exposure risk most people face is at home. The Surgeon General and the Environmental Protection Agency recommend that all homeowners check for the presence of radon. The best tests are those that take three to six months. For more information, contact your county public health department or visit the Environmental Protection Agency Web site.
Exposure to asbestos and other chemicals. Workplace exposure to asbestos and other cancer-causing agents — such as vinyl chloride, nickel chromates and coal products — also can increase your risk of developing lung cancer, especially if you're a smoker.
Race. Black Americans are at a higher risk of lung cancer. They also develop the disease at an earlier age and are less likely to survive. Doctors don't think there's a genetic reason for this disparity. Rather, it is more likely to be related to inequities in health care and to environmental factors.
Heredity. Research increasingly points to a genetic factor in lung cancer. Although smoking is undeniably the primary cause, people with a parent, sibling or other first-degree relative with lung cancer are at increased risk of the disease, whether they smoke or not.

Screening and diagnosis

Screening for lung cancer is controversial. The American Cancer Society currently doesn't recommend screening tests for lung cancer, even in high-risk individuals. But some doctors believe that smokers, especially those 50 years or older, should have annual screenings. The debate is becoming more heated with the increasing use of imaging tests such as helical and electron beam computerized tomography (CT) scans that could potentially detect early-stage cancers more effectively than older tests do — and with far less exposure to radiation. But CT screening has a serious drawback: It detects small, benign nodules that commonly occur in the lungs, leading, in some cases, to needless worry and unnecessary and invasive tests.

A standard chest X-ray can reveal an abnormal mass or nodule in your lungs. And a CT scan may show very small lesions and whether cancer has spread to other areas. But as with all types of cancer, lung cancer can be definitively diagnosed only by looking at a tissue sample (biopsy) under a microscope. The sample may be removed using one of the following techniques:

Sputum cytology. If you have a cough and are producing sputum, looking at the sputum under the microscope can sometimes reveal the presence of lung cancer cells. Before the test, you may be asked to breathe a mildly irritating mist to help you produce more sputum.
Bronchoscopy. In this test, a flexible tube called a bronchoscope is passed into your airway. The bronchoscope allows your doctor to look inside your lungs as well as to take a tissue sample for examination in the laboratory.
Mediastinoscopy. In this test, an instrument passed through a small incision at the base of your neck allows your doctor to take a biopsy of lymph nodes in your chest. This helps determine how far the cancer has spread and whether surgery is a reasonable option for removing the tumor.
Transthoracic needle biopsy. Using an X-ray or CT scan for guidance, your doctor takes a small needle and places it into a mass in your lung, removing a small piece for study.
Thoracentesis. If you have fluid in your chest cavity, your doctor can remove a sample by inserting a thin needle into your chest between the ribs. The fluid is then examined in the laboratory for presence of cancer cells. Removing a large amount of fluid with thoracentesis also can improve your breathing.
Video thoracoscopy. In this procedure, your doctor inserts a tube (endoscope) through a small incision between your ribs and partially collapses one of your lungs. This creates a space through which a pen-sized instrument with a video device is passed between the ribs and through your chest wall. Your doctor then can perform biopsies of nodules or masses while watching the procedure on a video screen. Your lung will expand again after the procedure.
Staging
Staging is a system of classifying information about cancer, including where and to what extent the cancer has spread. In many cases, Roman numerals are used to describe stages, with 0 being the least advanced and IV the most advanced. Your doctor uses this information to determine what treatment you need and to evaluate how your cancer might progress.

Non-small cell lung cancer
Non-small cell lung cancer is staged according to the size of the tumor, the level of lymph node involvement and the extent to which the cancer has spread. Stages of non-small cell lung cancer include:

Stage 0. At this stage, cancer is limited to the lining of the air passages and hasn't invaded lung tissue. Stage 0 cancers almost always are found during bronchoscopy, which is likely to have been performed to assess an abnormality on a chest X-ray. If found and treated promptly, cancers at this stage usually can be eliminated.
Stage I. Cancer at this stage has invaded the underlying lung tissue but hasn't spread to the lymph nodes.
Stage II. This stage cancer has spread to neighboring lymph nodes or invaded the chest wall.
Stage IIIA. At this stage, cancer has spread from the lung to lymph nodes in the center of the chest.
Stage IIIB. The cancer has spread locally to areas such as the heart, blood vessels, trachea and esophagus — all within the chest — or to lymph nodes in the area of the collarbone.
Stage IV. The cancer has spread to other parts of the body, such as the liver, bones or brain.
Small cell lung cancer
Small cell lung cancer is staged differently from non-small cell types. Rather than using numbers, it's classified as either limited or extensive:

Limited. Cancer is confined to one lung and to its neighboring lymph nodes.
Extensive. Cancer has spread beyond one lung and nearby lymph nodes, and may have invaded both lungs, more remote lymph nodes or other organs.
Staging tests
Tests to determine how far cancer has spread are of primary importance in planning treatments. In addition to CT scans, these tests include:

Magnetic resonance imaging (MRI). Instead of radiation, this test uses radio waves and high-powered magnets to produce internal images of your body. It's especially good at detecting tumors that have spread to the brain or spinal cord.
Positron emission tomography (PET) scan. Unlike other scanning techniques, a PET scan doesn't produce clear structural images of organs. Instead, it shows images containing areas of more or less intense color to provide information about chemical activity within certain organs and tissues. This chemical activity can indicate whether cancer cells have spread to nearby lymph nodes, even before the lymph nodes become enlarged, a distinct improvement over older staging methods. But PET scans need to be interpreted carefully because sometimes benign conditions can resemble cancer.


A PET scan, unlike a normal X-ray, can detect cancer before organ or gland enlargement occurs. Here a normal X-ray of the chest (left) is compared with a PET scan of the chest producing normal results (top right) and a PET scan revealing cancer that's spread to the lymph nodes (bottom right).

Complications

The lungs have an abundant supply of blood vessels and lymph channels, which means that lung cancer can spread to other parts of your body through your bloodstream and lymph system. Small cell cancer, in particular, is a fast-growing tumor that quickly spreads to other organs. At the time of diagnosis, this type of cancer has already spread in a majority of people. Without treatment, the tumor will continue to grow and may prove fatal within a matter of months.

Small cell cancer often responds to chemotherapy and radiation therapy, but even when there is a positive response to treatment, relapses usually occur within two years. Unfortunately, at that point the cancer usually isn't as responsive to further therapy.

In addition, some non-small cell lung cancers — even those identified at any early stage — may have already spread undetectably (micrometastasis) to lymph nodes and other organs. As a result, cancer can reappear months and even years after treatment.


Treatment

Treatments for lung cancer depend on the type and stage of cancer, as well as on your overall health. If you have emphysema, for instance, your poor lung function may prevent you from having surgery, even if you have a tumor that would otherwise be operable.

Other factors also come into play, no matter what type of lung cancer you have. There are times, for instance, when the potential side effects of treatment outweigh the benefits. When that is the case, your doctor may suggest comfort (supportive) care only. This means treating the symptoms the cancer is causing, such as pain and difficulty breathing, but not treating the cancer itself.

Small cell lung cancer
Because most small cell lung cancers have spread beyond the lungs by the time they're discovered, an operation usually isn't a treatment option. Instead, the most effective treatment is chemotherapy, either alone or in combination with radiation therapy.

Chemotherapy. This treatment uses drugs to kill cancer cells. In cases of small cell lung cancer, chemotherapy may be used to shrink the cancer, to slow the cancer's growth, to prevent it from spreading further, or to relieve symptoms and make you more comfortable (palliative care). A combination of drugs usually is given in a series of treatments over a period of weeks or months, with breaks in between so that your body can recover. Even so, because the drugs damage healthy cells along with malignant ones, they can cause serious side effects. In fact, for many people, side effects from chemotherapy are the most disturbing aspect of cancer treatment. Fast-growing cells such as those in your digestive tract, bone marrow and hair are especially likely to be affected. But although side effects are common, their severity depends on the drugs used and your response to them. Sometimes you may have few reactions. On the other hand, you may experience symptoms such as nausea and vomiting, dizziness, severe fatigue and an increased risk of infection. Ask your treatment team about the side effects of any treatment you're considering and the best ways to minimize those effects. If you choose to receive chemotherapy, be sure you understand the long- and short-term goals of your therapy and the overall risks and benefits.
Radiation therapy. This uses X-rays to kill cancer cells. In some cases, the radiation may come from outside your body (external radiation). In others, a radioactive substance may be placed inside needles, seeds or catheters and inserted into or near the cancer (internal radiation). The way in which radiation is delivered depends on the type and stage of the cancer being treated. Radiation therapy may be given before, during or after chemotherapy. In all cases, however, the goal of treatment is to destroy cancer cells while harming as little normal tissue as possible. Side effects of treatment may include redness and swelling of the skin where the radiation enters your body, a cough, shortness of breath, fatigue and sometimes difficulty swallowing if your esophagus is within the area receiving the radiation. You may not be a candidate for chest radiation if you have severe lung disease.

Small cell lung cancer often spreads to the brain. For that reason, your doctor may sometimes recommend brain radiation therapy to prevent cancer from metastasizing to that part of the body or to eliminate micrometastases that aren't yet detectable with imaging studies. Brain radiation therapy can cause short-term memory problems, fatigue, nausea and other serious side effects. If your cancer is in remission, discuss the risks and benefits of this treatment with your doctor.

Non-small cell lung cancer
Surgery is usually the best treatment for early-stage non-small cell lung cancer. In some cases, only the portion of the lung that contains the tumor is removed. In others, one lobe or even the entire lung may be taken. Surgery to remove all or part of a lung often involves opening one side of the chest, a procedure called a thoracotomy.

Operations to treat lung cancer include:

Wedge resection. In this operation, your doctor removes only the section of your lung that contains the tumor along with a margin of normal tissue.
Lobectomy. The most common type of lung cancer surgery, lobectomy involves removing an entire lobe of one lung.
Pneumonectomy. In this operation, an entire lung is removed. Because pneumonectomy will decrease lung function considerably, as well as lead to other complications, it's performed only when absolutely necessary and then only if your breathing capacity is sufficient to allow you to breathe with a single lung.
Sampling lymph nodes
No matter which operation is performed, your surgeon will sample lymph nodes from the center of your chest (mediastinum) and from the hilum — the region where the bronchus and blood vessels to the lungs originate. A pathologist usually examines the sample immediately, and your surgeon receives the report within 10 minutes. If cancer has spread to these nodes, your surgeon may decide not to remove any lung tissue. Unless the affected lymph nodes are at the base of the lobe containing the cancer, it's nearly impossible to remove all of the cancerous nodes. In addition, extensive lymph node involvement usually means that the cancer already has spread to other parts of the body, even though this spread may not yet have been detected.

Effects of surgery and your recovery
Surgery to remove lung tissue is a major operation. Depending on the extent and type of your surgery, you're likely to spend up to a week in the hospital. Once you return home, it may take weeks or even months to regain your strength. If you have other lung conditions, such as emphysema or bronchitis, your hospital stay and recovery may be even longer.

You're also likely to experience certain complications following surgery. The muscles of your chest and arm on the side where you had the operation will be very sore, for example, making it difficult to use the arm the way you used to. In that case, your doctor may recommend physical therapy or other rehabilitation program to help restore your strength and range of motion.

In addition, because you have less lung tissue, you initially may feel short of breath. Over time, however, your remaining lung tissue should expand, improving your ability to breathe. But if you have emphysema or other lung conditions, the shortness of breath may become worse.

No matter how much lung tissue is removed, you're likely to experience pain following your operation. Your doctor will work with you to ensure that you receive medication to keep you as comfortable as possible.

Treating advanced non-small cell lung cancer
More advanced non-small cell lung cancers are generally treated with chemotherapy, radiation, or a combination of both chemotherapy and radiation, although treatment of stage III non-small cell lung tumors is often individualized. Some people, for instance, may have surgery after first being treated with chemotherapy and radiation.

Still, because the best treatment for this stage of the disease isn't known, your doctor may suggest that you participate in a clinical trial — a research study that tries to improve current treatments or find new treatments for specific diseases. This can give you access to experimental therapies that might not otherwise be available. There are no guarantees with clinical trials, however, and you should fully understand the potential risks as well as possible benefits before undertaking this step.

New treatments
Researchers are developing new treatments for all types of cancer, including lung cancers, such as:

Erlotinib. This oral medication targets the epidermal growth factor receptors on the surface of cells that are involved in cell growth and proliferation. Abnormalities in these receptors, which can lead to the constant production of new cells, have been associated with several types of cancer. Erlotinib has been approved for use in treating recurrent non-small cell lung cancers and is being studied for use in other stages of the disease.
Bevacizumab. Given as an injection in conjunction with standard chemotherapy, this treatment helps stop the growth of blood vessels that supply nutrients to tumors. Bevacizumab has improved survival in some people with colorectal and lung cancers, but because the drug can have potentially fatal side effects, it's only used in certain cases.

Prevention

The best known way to prevent lung cancer is to not smoke. If you already smoke, quitting now can reduce your risk — even if you've smoked for years.

These measures also can help prevent lung cancer:

Avoid secondhand smoke. Breathing the smoke of others can be just as damaging as smoking is.
Test for radon. Have the radon levels in your home checked, especially if you live in an area where radon is known to be a problem.
Avoid carcinogens. Take precautions to protect yourself from exposure to toxic chemicals such as vinyl chloride, nickel chromates and coal products. Your risk of lung damage from these carcinogens increases if you also smoke.
Eat a healthy diet. Some studies have documented the relationship between food and cancer. The American Cancer Society recommends eating five to six servings of fruits and vegetables every day. In the case of lung cancer, certain foods seem to be especially protective. For example, a large study in China, where smoking rates are high, found that certain chemicals in cruciferous vegetables such as broccoli, cabbage and bok choy appeared to lower the risk of lung cancer. Other protective chemicals called cumestrans are found in beans, peas, spinach and sprouts. Isoflavones, the most common anticancer chemicals, occur in a wide range of foods, including soybeans, chickpeas and yams. Other studies have found a connection between consumption of large amounts of fresh fish — though not dried or salted fish — and a reduced rate of lung cancer. The American Cancer Society says more research is needed to establish a clear link, however.

Self-care

One of the best things you can do to care for yourself if you have lung cancer is also one of the most obvious — don't smoke. It's best to also avoid being around people who are smoking. Although it may be too late to prevent developing lung cancer, this will help optimize your lung function while you're being treated and improve your tolerance to treatment that may have some effects on your lungs.

Regular exercise, such as walking, exercise bicycling or swimming, will help you to maintain your general strength and stamina. Experts recommend at least 30 minutes of exercise on most days.

In addition, eating well and managing stress are both ways to promote your overall health and cope with any form of cancer. Eating well during cancer treatment can help you maintain your stamina and better cope with the side effects of chemotherapy or radiation. Good nutrition may also help you prevent infections and remain more active.

Eating suggestions
Cancer itself and some cancer treatments can affect your appetite. At times you simply may not feel like eating, or you may have nausea and vomiting as a result of chemotherapy. In that case, a registered dietitian can be especially helpful with food planning. The following suggestions also may help:

Eat small, frequent meals rather than three large ones.
Emphasize easily digested foods such as chicken soup or broth, plain boiled rice (or rice cooked in chicken broth), toast and baked potatoes. These are usually better tolerated than rich or spicy foods.
Don't worry if you just can't eat for a day or two.
Drink plenty of liquids, especially if you're not eating.

Coping skills

A diagnosis of cancer can be extremely challenging. It's important to remember that no matter what your concerns or prognosis, you're not alone. Here are some strategies and resources that may make dealing with cancer easier:

Know what to expect. Find out everything you can about your cancer — the type, the stage, your treatment options and their side effects. The more you know, the more active you can be in your own care. In addition to talking with your doctor, look for information in your local library and on the Internet. The National Cancer Institute will answer questions from the public. You can reach them at 800-4-CANCER, (800-422-6237), or contact the American Cancer Society (ACS) at 800-227-2345.
Be proactive. Although you may feel tired and discouraged, don't let others — including your family or your doctor — make important decisions for you. Take an active role in your treatment.
Maintain a strong support system. Having a support system can help you cope with any issues, pain and anxieties that might occur. Although friends and family can be your best allies, they sometimes may have trouble dealing with your illness. If so, the concern and understanding of a formal support group or others coping with cancer can be especially helpful. Although support groups aren't for everyone, they can be a good source for practical information. You may also find you develop deep and lasting bonds with people who are going through the same things you are.
Set reasonable goals. Having goals helps you feel in control and can give you a sense of purpose. But don't choose goals you can't possibly reach. You may not be able to work a 40-hour week, for example, but you may be able to work at least half time. In fact, many people find that continuing to work can be helpful.
Take time for yourself. Eating well, relaxing and getting enough rest can help combat the stress and fatigue of cancer. Also, plan ahead for the downtimes when you may need to rest more or limit what you do.
Stay active. A diagnosis of cancer doesn't mean you have to stop doing the things you enjoy or normally do. For the most part, if you feel well enough to do something, go ahead and do it. It's important to stay involved with life.

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