Lung cancer is the second most common cancer among both men and women and is the leading cause of cancer death in both sexes. Cigarette smoking causes almost 90% of lung cancers, and passive smoking contributes to the development of lung cancer among nonsmokers.
What is Lung Cancer?
Cancer is a group of many related diseases that begin in cells, the body's basic unit of life. The body is made up of many types of cells, and normally, cells grow and divide to produce more cells only when the body needs them. Sometimes, however, cells keep dividing when new cells are not needed. These extra cells form a mass of tissue, called a growth or tumor. There are two types or tumor, benign and malignant.
Benign tumors are not cancer. They can usually be removed and, in most cases, they do not come back. Cells from benign tumors do not spread to other parts of the body and are not a threat to life.
Malignant tumors are cancer. Cancer cells can invade and damage tissues and organs near the tumor, and can break away from a malignant tumor and enter the lymphatic system or the bloodstream. The spread of cancer is called metastasis.
Cancers that begin in the lungs are divided into two major types, called non-small cell lung cancer and small cell lung cancer, depending on how the cells look under a microscope. Each type of lung cancer grows and spreads in different ways and is treated differently.
Non-small cell lung cancer is the most common type, and it generally grows and spreads more slowly than small cell lung cancer. There are three main types of non-small cell lung cancer named for the type of cells in which the cancer develops: squamous cell carcinoma (also called epidermoid carcinoma), adenocarcinoma and large cell carcinoma.
Small cell lung cancer, sometimes called oat cell cancer, is less common than non-small cell lung cancer. This type of lung cancer grows more quickly and is more likely to spread to other organs in the body.
What causes Lung Cancer?
Several causes of lung cancer have been discovered, most of which are related to the use of tobacco. The following list identifies the risk factors for lung cancer:
Cigarettes -- Smoking cigarettes causes lung cancer. Carcinogens in the tobacco damage the cells in the lungs, and over time, the damaged cells may become cancerous. The risk of a cigarette smoker developing lung cancer is dependent on the number of cigarettes smoked each day, the age at which smoking began and how long the person has smoked. Stopping smoking greatly reduces the risk of developing lung cancer.
Cigars and Pipes -- Cigar and pipe smokers also have a higher risk of lung cancer than nonsmokers. The risk of developing lung cancer is dependent on the number of pipes or cigars smoked each day and the number of years a person has smoked
Environmental Tobacco Smoke -- The chance of developing lung cancer is increased by exposure to environmental tobacco smoke (ETS), which is the smoke in the air when someone else smokes. Exposure to ETS, or secondhand smoke, is called involuntary or passive smoking.
Radon is an invisible, odorless, and tasteless radioactive gas that occurs naturally in soil and rocks. Exposure to radon (in mines or even houses) can cause damage to the lungs that may lead to lung cancer.
Asbestos is the name of a group of minerals that occur naturally as fibers and are used in certain industries. Asbestos fibers tend to break easily into particles that can float in the air and stick to clothes. When the particles are inhaled, they can lodge in the lungs, damaging cells and increasing the risk for lung cancer.
Pollution -- There is a link between lung cancer and exposure to certain air pollutants, such as by-products of the combustion of diesel and other fossil fuels. This relationship has not been clearly defined, however and more research is being done.
Lung Diseases -- Certain lung diseases, such as tuberculosis (TB), increase the risk of developing lung cancer. Lung cancer tends to develop in areas of the lung that are scarred from TB.
Personal History -- A person who has had lung cancer once is more likely to develop a second lung cancer compared with a person who has never had lung cancer. Quitting smoking after lung cancer is diagnosed may prevent the development of a second lung cancer.
The best way to prevent lung cancer is to quit, or never start, smoking.
Symptoms of Lung Cancer
Common signs and symptoms of lung cancer include:
- A cough that doesn't go away and gets worse over time
- Constant chest pain
- Coughing up blood
- Shortness of breath, wheezing, or hoarseness
- Repeated problems with pneumonia or bronchitis
- Swelling of the neck and face
- Loss of appetite or weight loss
These symptoms may be caused by lung cancer or by other conditions. It is important to check with a doctor.
Diagnosing Lung Cancer
To help find the cause of symptoms, the doctor assesses the medical history, including smoking history and family history of cancer. The doctor also performs a physical exam and may order a chest x-ray and other tests. 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 is where a bronchoscope (a thin, lighted tube) is put into the mouth or nose and down through the windpipe to look into the breathing passages. Cells or small samples of tissue can be taken through this tube.
Needle aspiration involves inserting a needle through the chest into the tumor to remove a sample of tissue.
Thoracentesis is a procedure where a needle is used to take a sample of the fluid that surrounds the lungs to check for cancer cells.
Thoracotomy is a major operation where the chest is opened.
Staging the Disease
If the diagnosis is cancer, staging is done to determine the stage (or extent) of the disease, to find out whether the cancer has spread, and if so, to which parts of the body. Lung cancer can often spread to the brain or bones. Some tests used to determine whether the cancer has spread include:
- CAT (or CT) Scan (computed tomography). A computer linked to an x-ray machine creates a series of detailed pictures of areas inside the body.
- MRI (Magnetic Resonance Imaging) A powerful magnet linked to a computer makes detailed pictures of areas inside the body.
- Radionuclide 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 is a type of radionuclide scanning, and can show whether cancer has spread to the bones. A small amount of radioactive substance is injected into a vein. It travels through the bloodstream and collects in areas of abnormal bone growth. An instrument called a scanner measures the radioactivity levels in these areas and records them on x-ray film.
- Mediastinoscopy can help show whether the cancer has spread to the lymph nodes in the chest. Using a lighted viewing instrument, called a scope, the center of the chest is examined and nearby lymph nodes. In mediastinoscopy, the scope is inserted through a small incision in the neck; in mediastinotomy, the incision is made in the chest. In either procedure, the scope is used to remove a tissue sample under general anesthetic.
Methods of Treatment and Side Effects
Treatment depends on a number of factors, including the type of lung cancer, the size, location, and extent of the tumor, and the general health of the patient. Many different treatments and combinations of treatments may be used to control lung cancer, and/or to improve quality of life by reducing symptoms.
Surgery is an operation to remove the cancer. The type of surgery performed depends on the location of the tumor. An operation to remove only a small part of the lung is called a segmental or wedge resection.
When the entire lobe of the lung is removed, the procedure is called a lobectomy. The removal of an entire lung is called pneumonectomyis.
Lung cancer surgery is major surgery. After an operation, air and fluid tend to collect in the chest. Patients often need help turning over, coughing, and breathing deeply. Pain or weakness in the chest and the arm and shortness of breath are common side effects of lung cancer surgery. Patients may need several weeks or months to regain their energy and strength.
Chemotherapy is the use of anticancer drugs to kill cancer cells throughout the body. Even after cancer has been removed from the lung, cancer cells may still be present in nearby tissue or elsewhere in the body. Chemotherapy may be used to control cancer growth or to relieve symptoms.
Side effects depend largely on the specific drugs and the dose (amount of drug given). Common side effects of chemotherapy include nausea and vomiting, hair loss, mouth sores, and fatigue.
Radiation therapy (radiotherapy) involves the use of high-energy rays to kill cancer cells. Radiation therapy is directed to a limited area and affects the cancer cells only in that area. Radiation therapy may be used before surgery to shrink a tumor, or after surgery to destroy any cancer cells that remain in the treated area. Radiation therapy, often combined with chemotherapy, is often used as primary treatment instead of surgery. Radiation therapy may also be used to relieve symptoms such as shortness of breath. Radiation for the treatment of lung cancer most often comes from a machine (external radiation). The radiation can also come from an implant (a small container of radioactive material) placed directly into or near the tumor (internal radiation).
Side effects of radiation therapy depend mainly on the part of the body that is treated and the treatment dose. Common side effects of radiation therapy are a dry, sore throat; difficulty swallowing; fatigue; skin changes at the site of treatment; and loss of appetite.
Photodynamic therapy (PDT), a type of laser therapy, involves the use of a special chemical that is injected into the bloodstream and absorbed by cells all over the body. The chemical rapidly leaves normal cells but remains in cancer cells for a longer time. A laser light aimed at the cancer activates the chemical, which then kills the cancer cells that have absorbed it. Photodynamic therapy may be used to reduce symptoms of lung cancer (to control bleeding or to relieve breathing problems due to blocked airways) when the cancer cannot be removed through surgery. Photodynamic therapy may also be used to treat very small tumors in patients for whom the usual treatments for lung cancer are not appropriate.
PDT makes the skin and eyes sensitive to light for 6 weeks or more after treatment. Patients are advised to avoid direct sunlight and bright indoor light for at least 6 weeks. If patients must go outdoors, they need to wear protective clothing, including sunglasses. Other temporary side effects of PDT may include coughing, trouble swallowing, and painful breathing or shortness of breath. Patients should talk with their doctor about what to do if the skin becomes blistered, red, or swollen.
Treating Non-small Cell Lung Cancer
Surgery is the most common way to treat non-small lung cancer. Radiation therapy and chemotherapy may also be used to slow the progress of the disease and to manage symptoms.
Drugs used in the Treatment of Non-Small Cell Lung Cancer
Treating Small Cell Lung Cancer
Small cell lung cancer spreads quickly. In many cases, cancer cells have already spread to other parts of the body when the disease is diagnosed. In order to reach cancer cells throughout the body, doctors almost always use chemotherapy. Treatment may also include radiation therapy aimed at the tumor in the lung or tumors in other parts of the body. Surgery is part of the treatment plan for a small number of patients with small cell lung cancer.