Lung cancer

Definition
Lung cancer is the development of malignant cells in the lungs. Lung cancer is the leading cause of cancer-related deaths in the United States for both men and women.

Anatomy
The lungs are located in the pleural cavity of the thorax (chest) inside the rib cage. The right lung has three sections, or lobes, and the left lung has two. Both lungs are made up of a series of passageways through which air travels. Air enters the trachea (windpipe), and travels to the two main airways in the lungs. These airways, called bronchi, divide into smaller airways called bronchioles. At the end of the bronchioles are tiny air sacs called alveoli.

Types of lung cancer
There are two main types of lung cancer: non-small cell lung cancer and small cell lung cancer.
Non-small-cell lung cancer (NSCLC) accounts for approximately 80 percent of lung cancer cases. The three categories of non-small cell lung cancer include:

squamous cell carcinoma (cancer that forms in the lining of the airways)
adenocarcinoma (cancer that forms in the mucous-producing cells of the lungs)
large cell carcinoma (cancer that forms in the outer areas of the lungs)
Small-cell lung cancer (SCLC) grows and spreads more rapidly than non-small cell lung cancer. Sometimes this type of cancer is called oat cell cancer because the cells resemble oats under the microscope.

Less common forms of lung cancer not included in the two main types are mesothelioma, carcinoid, blastoma, sarcoma and melanoma.


Causes/associated factors
Cigarette smoking is the most common cause of lung cancer. In fact, smoking accounts for up to 90 percent of all lung cancer cases. Smoking cigars or pipes also increases the risk of developing lung cancer. The relationship is simple -- harmful substances in tobacco smoke called carcinogens damage the cells in the lungs. The risk of developing lung cancer depends on several factors, including how many cigarettes you smoke per day, how long you've smoked, and how old you were when you began smoking.
Exposure to radon gas is the second leading cause of lung cancer. Radon is a naturally occurring radioactive gas that forms when uranium breaks down in the soil. This colorless, odorless gas can enter houses from cracks in the foundation.

Other contributing factors include exposure to asbestos, secondhand smoke and pollution in the environment.


Signs/symptoms
Often, lung cancer has no early symptoms. When symptoms do develop, they may include:
chronic cough
hoarseness
chest pain
coughing up blood
shortness of breath
wheezing
frequent episodes of bronchitis or pneumonia

Diagnosis
Your doctor will do a physical exam and ask questions about your symptoms and medical history. You may also be asked about your smoking history and exposure to environmental and occupational substances. You may need blood tests. If you have a cough that produces sputum, a sample may be examined for cancer cells with a test called sputum cytology. A standard chest X-ray or computed tomography scan (CT scan) of your chest may be done as well.
Your doctor may need to do a biopsy (examine a tissue sample taken from your lungs) to make the final diagnosis. The biopsy may be done through:

Bronchoscopy: The doctor examines the lungs and takes the tissue sample through a flexible tube that's passed down your airway.

Mediastinoscopy: The doctor takes the tissue sample through an instrument that's passed through an incision at the base of your neck. This procedure is done under anesthesia.

Transthoracic needle biopsy: With an X-ray or CT scan for guidance, the doctor inserts a needle into a tumor in your lung to remove a small piece for examination.

Thoracentesis: When fluid has been identified in the lungs, the doctor inserts a needle into the lungs to withdraw a fluid sample for examination. This procedure may also be done to remove fluid if it's causing breathing difficulty.

Video thoracoscopy: The doctor inserts a tube through a small incision in the chest wall to collapse one lung. Then, an instrument through which he or she can take a tissue sample under video guidance is attached to a video device and inserted through the incision.
Staging
When lung cancer has been diagnosed and the specific type has been identified, the doctor stages the cancer. This process helps the doctor determine the extent of the disease, the prognosis and the most appropriate treatment options. Staging of non-small cell lung cancer is based on the TNM system: tumor, node and metastasis (the spread of the primary tumor to other unrelated sites in the body). The stages range from stage 0 (lowest) to IV (most advanced).

Staging of small cell lung cancer is divided into two categories: limited stage and extensive stage. Limited stage small cell lung cancer is confined to one lung and nearby lymph nodes. Extensive stage small cell lung cancer has spread beyond one lung and nearby lymph nodes. Extensive stage may involve other organs as well.

The staging process includes biopsies, X-rays, CT scans and magnetic resonance imaging (MRI) scans. Other diagnostic tests may include:

Radionuclide scan: A radionuclide scan can help the doctor determine if the cancer has spread to other organs, such as the brain or liver. You'll receive a small dose of a radioactive substance either orally in liquid form or through an injection. Any abnormal areas will then appear on the films from the scan.

Bone scan: A bone scan can help the doctor determine if the cancer has spread to the bone. You'll be given an injection of radioactive material, which will be attracted to areas of the bone that have cancer or other diseases. Any areas of diseased bone will then appear on the films from the bone scan.

Treatment
Treatment is based on the type of lung cancer and the stage at which it's diagnosed. Standard treatments include surgery, chemotherapy, radiation therapy or a combination of these treatments. In some advanced cases, the goal of treatment is not to remove the cancer but alleviate the symptoms, including pain.
Surgery
The cancerous area of the lung may be surgically removed when the cancer is confined to a limited area. Typically, surgery is only an option for non-small cell cancer. The amount of lung removed depends on how far the cancer has spread. If the tumor involves a small section of the lung, a wedge resection may be done to remove the cancerous tissue. If an entire lobe is affected, a lobectomy may be done to remove the entire lobe. If the entire lung is involved, the whole lung may be removed in a procedure called pneumonectomy.

During surgery, additional lymph nodes may be taken for examination. If the doctor discovers the cancer has spread further than originally thought, the surgery might be stopped without any lung tissue being removed. Keep in mind that surgery alone rarely cures lung cancer. Chemotherapy before or after surgery or radiation treatment done in combination with surgery may improve the outcome.

Benefits of surgery: Surgically removing all or as much of the cancer as possible increases the chance of survival.

Risks of surgery: Depending on how much of the lung is removed, recovery can be slow and painful. You may be hospitalized for about a week, followed by a month or more of limited activity.
Chemotherapy
Chemotherapy is treatment with medication that kills cancer cells. It's the main treatment for small cell lung cancer. Chemotherapy is typically given intravenously, but may also be given orally in tablet form. It may be done before surgery to shrink the tumor or after surgery to prevent the cancer from recurring or spreading.

Chemotherapy usually involves a series of outpatient treatments, each separated by a recovery period. Common chemotherapy medications include paclitaxel, docetaxel, carboplatin, gemcitabine, cisplatin and vinorelbine. These medications are often given in combinations that are more effective than any single medication.

Benefits of chemotherapy: Chemotherapy treats cancer cells that may have spread throughout the body, rather than just those in the area of the tumor. If the cancer is advanced, chemotherapy can help you live longer.

Risks of chemotherapy: Along with the cancer cells, chemotherapy also affects normal cells. This can cause side effects such as nausea, vomiting, diarrhea, fatigue, appetite loss, hair loss, mouth sores and changes in menstrual cycle. Specific side effects depend on the type of medication, the amount taken and the length of treatment. Newer chemotherapy medications such as paclitaxel (brand name Taxol, for example) and docetaxel (Taxotere) have been found to have fewer side effects.
Radiation therapy
Radiation therapy uses high-energy X-rays to kill cancer cells. It's given externally through a beam of radiation directed toward the affected area from a radiation machine.

Radiation treatments are given five days a week for about six weeks. Radiation therapy may be done at any cancer stage. It may also be given to prevent cancer from developing in other areas of the body. For example, radiation may be given to prevent tumors from forming in the brain.

Benefits of radiation: Radiation therapy can kill cancer cells that remain in the lung, lymph nodes or other tissues after surgery and reduce the risk of the cancer returning. This can provide relief from pain and make breathing easier if your airways are blocked by a tumor.

Risks of radiation: The radiation may damage nearby normal tissue, causing a range of side effects. During the treatment you may feel very tired and the skin in the treatment area may become irritated. Other possible side effects include lung inflammation or the sac around the heart (a condition known as pericarditis) and arm weakness, numbness or swelling.
Photodynamic therapy
Photodynamic therapy (PDT) uses a laser light in combination with a chemical that's injected into the bloodstream and absorbed by cancer cells. The laser activates the chemical, which kills the cancer cells.

Benefits of photodynamic therapy: Photodynamic therapy may be used to treat very small tumors or relieve symptoms from larger tumors that are causing pain or making breathing difficult.

Risks of photodynamic therapy: Photodynamic therapy makes the skin and eyes sensitive to light for six weeks or more following treatment. Other possible side effects include coughing, difficulty swallowing, painful breathing or shortness of breath.

Complications
Lung cancer often metastasizes, or spreads, to other tissues and nearby lymph nodes. It may also spread to the brain, bones and liver. Even with successful treatment, relapses often occur within two years.

Pregnancy-specific information
Pregnancy does not increase the risk of developing lung cancer. If you have lung cancer, treatment measures may differ from those recommended for other adults. Ask your doctor for details.

Senior-specific information
The risk for developing lung cancer increases with age, especially after age 75 or if you smoke.

Prevention
The best way to prevent lung cancer is to stop smoking -- or never smoke at all. Remember, it's never too late to benefit from quitting smoking. It's also helpful to limit exposure to secondhand smoke. Avoid smoky environments, and don't allow others to smoke in your home.
At home, install radon detectors. (Results from the most accurate tests take three to six months.) At work, be aware of potential hazards. Wear protective masks if you're exposed to dust or fumes.

Currently, the American Cancer Society doesn't recommend screening tests for lung cancer. Some doctors recommend annual chest X-rays for smokers over age 50, although on its own this practice has not proved to be an effective way to detect lung cancer. A newer type of CT scan known as a spiral CT is being studied to determine if it can be used to detect lung cancer at an early stage. Preliminary results show that the scan's more detailed images may actually be a drawback, however, showing small lumps that were benign after further, more extensive tests.