Lung cancer

What is lung cancer?

Lung cancer is a malignant (cancerous) tumor that starts from cells of the lung.

The lungs are a pair of sponge-like organs found in the chest that take in oxygen when we breathe in and get rid of carbon dioxide when we breathe out. The right lung is a bit larger than the left lung, which is smaller to accommodate for the size of the heart on the left side of the body. The right lung has three sections, called lobes, and the left lung has two.

The majority of lung cancers start in the lining of the bronchi, which are tubes leading from the windpipe (or trachea) into the lungs. However, they can also begin in other areas such as the trachea, bronchioles (smaller tubes branching off the bronchi) or alveoli (tiny air sacs at the end of bronchioles). Lung cancer generally takes many years to develop and can be life threatening because it is often found after cancer cells have spread to other parts of the body (metastasized).

There are two main types of lung cancer, depending on how the cells look under a microscope: small cell lung cancer and non-small cell lung cancer. The different types of lung cancer progress in different ways and are therefore treated differently.

Small cell lung cancer (SCLC)

As the name implies, small cell lung cancer cells are small. They can multiply quickly and are more likely to metastasize to the lymph nodes and other organs in the body, such as the brain, liver and bones. Also known as oat cell cancer or small cell undifferentiated carcinoma, SCLC is less common than non-small cell lung cancer, accounting for about 20 percent of all lung cancers.

Non-small cell lung cancer (NSCLC)

Non-small cell lung cancer generally grows and spreads more slowly compared with small cell lung cancer. It accounts for almost 80 percent of lung cancers and is the most common type of the disease. There are three main types of non-small cell lung cancer, which are based on the type of cells in which the cancer develops:

• Squamous cell carcinoma is a cancer that begins in squamous cells, which are thin, flat cells found in the passages of the respiratory and digestive tracts as well as in the surface of the skin and the lining of the hollow organs of the body. This type of NSCLC is linked to a history of smoking and usually found centrally, near a bronchus. It is also called epidermoid carcinoma.
• Adenocarcinoma describes cancers that begin in cells that line certain internal organs and have glandular (secretory) properties. Adenocarcinoma NSCLC is most often found in the outer region of the lung.
• Large-cell undifferentiated carcinoma is a type of lung cancer in which the cells are large and look abnormal when viewed under a microscope. It can be found in any part of the lung and tends to grow and spread rapidly.

If the cancer has features of both small cell and non-small cell lung cancers, it is called mixed small cell/large cell cancer.

Who gets lung cancer?

According to the American Cancer Society, there will be about 213,380 new cases of lung cancer in the United States in 2007, and approximately 160,390 people will die of the disease, accounting for about 29 percent of all cancer deaths. It is the leading cause of cancer death for both men and women, killing more people than colon, breast and prostate cancers combined. Most people diagnosed with lung cancer are over the age of 65.

What causes lung cancer?

Although smoking is by far the leading risk factor for lung cancer, it is known that there are several other risk factors linked to the disease. Some of the risk factors for lung cancer are discussed below.

Smoking

Tobacco smoking is believed to be responsible for 80 percent of all cases of lung cancer. The risk of lung cancer increases with the length of time a person has been smoking, the number of packs per day smoked, and how deeply the smoke is inhaled. However, if a person quits smoking before lung cancer develops, the lung tissue slowly returns to normal, which lowers the risk of lung cancer.

Some people think that smoking cigars and pipes is less harmful than smoking cigarettes. However, research has shown that cigar and pipe smoking are almost as likely to cause lung cancer as cigarette smoking. Even cigar and pipe smokers who do not inhale are at increased risk for lung, mouth and other types of cancers.

Secondhand smoke, also called environmental tobacco smoke, describes the smoke in the air when someone else smokes. Exposure to secondhand smoke is called involuntary or passive smoking and increases lung cancer risk. For example, nonsmoking spouses of smokers and people exposed to tobacco smoke in the workplace are more likely to get lung cancer.

Asbestos

Asbestos is any of several minerals that occur naturally as fibers. These fibers tend to break easily into particles, which can float in the air and become inhaled, where they can lodge in the lungs, damaging cells and increasing the risk for lung cancer. Formerly used as fireproof insulating materials, asbestos is rarely used today in the workplace or in home products, as it has since been implicated as a cause of certain cancers.

Workers who have been exposed to large amounts of asbestos — such as those in industries like shipbuilding, insulation work, and asbestos mining and manufacturing — have a higher risk of getting lung cancer. The risk of lung cancer is even higher among asbestos workers who also smoke.

Radon

Radon is an invisible, odorless and tasteless radioactive gas that occurs naturally in soil and rock. It can cause damage to the lungs that may lead to lung cancer. People who work in mines may be exposed to radon; occasionally, radon can also accumulate indoors. Radon levels in homes may be measured by a kit found in most hardware stores.

Marijuana

Many of the carcinogens found in tobacco are also found in marijuana, which actually has more tar than regular cigarettes. Research suggests that marijuana may also cause cancers of the mouth and throat.

Lung diseases

Certain lung diseases, such as tuberculosis and some types of pneumonia, often leave scars on the lung that can increase the risk of developing lung cancer.

Personal and family history

A person who has had lung cancer once is at increased risk for developing a second lung cancer. Siblings and children of people who have had lung cancer may also have a slightly higher risk.

Can lung cancer be prevented?

The best way to prevent lung cancer is not to smoke and to avoid exposure to secondhand smoke. Also, protect yourself from any cancer-causing chemicals you may be exposed to at work and consider testing radon levels in your home.

What are the symptoms of lung cancer?

Because most lung cancers do not cause any symptoms until they have spread, only about 15 percent of lung cancers are found in the early stages. When lung cancer is found early, it is often as a result of a chest X-ray, CT scan or other test that was being done for another reason. Symptoms of lung cancer may include:

• A cough that does not go away and gets worse over time
• Constant chest pain, often made worse by deep breathing
• Hoarseness
• Weight loss and loss of appetite
• Coughing up blood
• Shortness of breath
• Recurring infections such as bronchitis and pneumonia
• New onset of wheezing
• Swelling of the neck and face

Remember that these symptoms may be caused by conditions other than lung cancer. It is important to check with a doctor.

How is lung cancer diagnosed?

If there is any reason to suspect lung cancer, the doctor will take a medical history and conduct a physical exam. The doctor may also order a chest X-ray and other tests. If lung cancer is suspected, sputum cytology (the microscopic examination of cells obtained from a deep-cough sample of mucus in the lungs) is a simple test that may be useful in detecting lung cancer.

To confirm the presence of lung cancer, the doctor must examine tissue from the lung. A biopsy — the removal of a small sample of tissue for examination under a microscope by a pathologist — can show whether a person has cancer. A number of procedures may be used to obtain this tissue:

• Bronchoscopy: The doctor puts a bronchoscope (a thin, lighted tube) into the mouth or nose and down through the windpipe and into the bronchi. This test can help find tumors or it can be used to take samples of tissue or fluids to see if cancer cells are present.
  
  
• Needle aspiration: A needle is inserted through the chest into the tumor to remove a sample of tissue.
  
  
• Thoracentesis: Using a needle, the doctor removes a sample of the fluid that surrounds the lungs. This test is done to check whether fluid around the lungs is caused by cancer or by a benign condition such as heart failure or an infection.
  
  
• Thoracotomy: Surgery to open the chest is sometimes needed to diagnose lung cancer. This procedure is a major operation performed in a hospital.

If the diagnosis is cancer, the doctor will conduct additional tests to determine the stage (or extent) of the disease (stages of lung cancer are discussed later). Some tests used to determine the cancer stage include:

• Computed tomography (CT) scan: A CT scan is an X-ray procedure in which the X-ray beam moves around the body, taking pictures from different angles. These images are combined by a computer to produce a detailed cross-sectional picture of the inside of the body.
  
  
• Magnetic resonance imaging (MRI): MRI uses large magnets and radio waves to produce computer-generated cross-sectional pictures of internal organs.
  
  
• Radionuclide scanning: Scanning can show whether cancer has spread to other organs, such as the liver. The patient swallows or receives an injection of a mildly radioactive substance. A machine (scanner) measures and records the level of radioactivity in certain organs to reveal abnormal areas.
  
  
• Bone scan: A bone scan is a type of radionuclide scanning that can show whether cancer has spread to the bones.
  
  
• Mediastinoscopy: A mediastinoscopy can help show whether the cancer has spread to the lymph nodes in the chest. With the patient asleep, tissue samples are taken from the lymph nodes along the windpipe through a small hole cut into the neck. Examining the tissue under a microscope can show if cancer cells are present.
  
  
• Bone marrow biopsy: A needle is used to remove a small piece of bone, usually from the back of the hipbone, and the sample is checked for cancer cells.
  
  
• Blood tests: Certain blood tests are often done to help see if the lung cancer has spread to the liver or bones.

What are the stages of lung cancer?

Staging is the process of finding out how far the cancer has spread. It is very important because, to a large extent, treatment and outlook for recovery depend on the stage of the cancer. There are different staging systems for small cell and non-small cell lung cancers.

Small cell lung cancer staging

Non-small cell lung cancer staging

How is lung cancer treated?

The treatment options for lung cancer include surgery, chemotherapy, radiation therapy and photodynamic treatment, either alone or in combination, depending on the type and stage of the cancer.

Surgery

Surgery is an operation to remove the cancer. Depending on the type and stage of the cancer and the location of the tumor in the lung, surgery may be used to remove the tumor and some of the lung tissue around it. There are three main types of surgery for lung cancer:

• Segmental or wedge resection: an operation to remove only a small part of the lung
• Lobectomy: a procedure in which an entire lobe of the lung is removed
• Pneumonectomy: the surgical removal of an entire lung

Some tumors are inoperable (cannot be removed by surgery) because of the size or location, and some patients cannot have surgery for other medical reasons.

Chemotherapy

Chemotherapy is the use of anticancer drugs to kill cancer cells throughout the body. Even after the tumor has been removed from the lung, cancer cells may still be present in nearby tissue or elsewhere in the body. Most chemotherapy drugs are either injected or administered as a pill, allowing them to enter the bloodstream and spread throughout body, which makes the treatment useful for cancers that have spread to distant organs. Chemotherapy may be used to control cancer growth or to relieve symptoms. Although chemotherapy drugs kill cancer cells, they can also damage some normal cells, which can lead to side effects.

Radiation therapy

Radiation therapy, also called radiotherapy, involves the use of high-energy rays (such as X-rays) to shrink or kill cancer cells, or to relieve certain symptoms. Radiation therapy is directed to a limited area and affects the cancer cells only in that area. It may be used before surgery to shrink a tumor, or after surgery to destroy any cancer cells that remain in the treated area. Doctors may also use radiation therapy, often combined with chemotherapy, as primary treatment for lung cancer instead of surgery. The radiation may come from outside the body (external radiation) or from radioactive materials placed directly in the tumor (internal or implant radiation). External radiation is the type most often used to treat lung cancer.

Photodynamic therapy

Photodynamic therapy (PDT) is a type of laser therapy that is sometimes used to reduce symptoms of the disease or to treat very small tumors in patients for whom the usual lung cancer treatments are not appropriate. A special chemical is injected into the bloodstream and absorbed by cells in the body. In normal cells, the chemical does not remain and leaves rapidly. However, it stays in cancer cells for a longer time, allowing them to be targeted by a laser light that, when aimed at the cancer, activates the chemical to kill the cancer cells that have absorbed it.

Clinical trials

Clinical trials of new treatment methods can be important treatment options for lung cancer patients.

Learn more about clinical trials.

What are some questions I can ask my doctor?

Your doctor is your best resource for information so you should feel free to ask any questions that are on your mind. Below are some questions you might want to ask your doctor.

• Exactly what type of lung cancer do I have?
• May I have a copy of my pathology report?
• Has my cancer spread to lymph nodes or internal organs?
• What is the stage of my cancer? What does that mean in my case?
• What treatment choices do I have? What do you recommend? Why?
• What are the risks or side effects of different treatments?
• How long will each course of treatment last?
• Will I be out of work? For how long?
• What are the chances of my cancer coming back with the treatment you suggest?
• Am I eligible for any clinical trials?
• What are my chances of survival, based on my cancer, as you see it?
• After treatment, how often do I need to be checked? What type of follow-up care should I have?

Additional resources