What Is It?
Lung cancer usually occurs because some outside factor, called a carcinogen, has triggered the growth of abnormal, cancerous cells in the lung. These cancerous cells multiply out of control and eventually form a mass called a tumor. As the tumor grows, it destroys nearby areas of the lung. Eventually, the tumor’s abnormal cells can spread (metastasize) to nearby lymph nodes and to distant organs, such as the brain. In most cases, the carcinogens that trigger lung cancer are chemicals found in cigarette smoke.
Lung cancers are divided into two basic groups, nonsmall-cell lung cancer and small-cell lung cancer, based on the microscopic appearance of the tumor cells. These two groups are treated differently.
NonSmall-Cell Lung Cancer
Nonsmall-cell lung cancer is more likely than small-cell cancer to be localized at the time of diagnosis. It also is more likely than small-cell cancer to be treatable with surgery or radiation therapy, but it often shows a poor response to chemotherapy. Nonsmall-cell lung cancer is divided into several subgroups based on the microscopic appearance of the cancerous cells:
- Adenocarcinoma (32 percent of cases) — This is the most common type of lung cancer. Although it is related to smoking, it is also the most common type of lung cancer seen in nonsmokers. Adenocarcinoma is the most frequent form of lung cancer seen in women and in people younger than 45. It usually develops near the edge of the lung and can involve the membrane covering the lung, called the pleura.
- Squamous-cell (epidermoid) carcinoma (30 percent of cases) — This form of lung cancer tends to develop as an abnormal mass near the center of the lungs. As the mass enlarges, it can protrude into one of the larger air passages, called the bronchi. In 10 percent to 20 percent of cases, the tumor forms a cavity in the lungs (cavitates).
- Large-cell carcinoma (10 percent to 20 percent of cases) — Like adenocarcinoma, large-cell carcinoma tends to develop at the edge of the lungs and spread to the pleura. Like squamous (epidermoid) carcinoma, it cavitates in 10 percent to 20 percent of patients.
- Adenosquamous carcinoma, undifferentiated carcinoma, and bronchioloalveolar carcinoma — These are three relatively rare forms of nonsmall-cell lung cancer.
Small-Cell Lung Cancer
At the time of diagnosis, small-cell lung cancer is more likely than nonsmall-cell cancer to have spread beyond the boundaries of the lung. This typically makes it almost impossible to cure with surgery. However, chemotherapy or radiation therapy can be used to manage the cancer. Small-cell cancers account for about 20 percent of all lung cancers.
Currently, about 170,000 people in the United States are diagnosed with lung cancer each year, and the illness is the country’s leading cause of cancer deaths. Lung cancer most commonly strikes people between the ages of 55 and 65, and smokers account for 86 percent to 90 percent of all cases. Risk factors for lung cancer include:
- Cigarette smoking — Smokers are 13 times more likely to develop lung cancer than nonsmokers.
- Passive cigarette smoking — Nonsmokers who inhale the cigarette fumes of smokers have an increased risk of developing lung cancer. Health experts believe that passive (secondhand) cigarette smoke causes 3,000 lung cancer deaths in nonsmokers each year.
- Exposure to radon gas — Radon is a colorless, odorless radioactive gas that is formed in the ground. It seeps into the lower floors of homes and public buildings, and it also can contaminate drinking water. Radon exposure is the second most important risk factor for lung cancer after smoking. Estimates suggest that it accounts for more than 7,000 lung cancer deaths annually.
- Exposure to asbestos — Asbestos is a family of fibrous minerals that occur in underground deposits. Asbestos is used in home insulation, fire-proofing, tiles for floors and ceilings, automobile brake linings, and other products. It is believed that irritating asbestos fibers can cause cancer. The risk of lung cancer is higher in workers who are exposed to asbestos on the job (miners, construction workers, auto mechanics who work with brakes), as well as in people who live or work in buildings where asbestos-containing building products are deteriorating. In general, asbestos exposure tends to increase the risk of squamous cell carcinoma or adenocarcinoma, especially in people who also smoke cigarettes.
- Work-related exposure to substances — Substances associated with lung cancer include uranium, arsenic, vinyl chloride, nickel chromates, coal products, mustard gas, chloromethyl ethers, gasoline, diesel exhaust, and high levels of talc dust.
In 5 percent to 15 percent of cases, a cancerous lung tumor is detected on a routine chest X-ray in a person who doesn’t have any symptoms. However, most lung cancer patients have one or more of the following symptoms:
- Coughing up blood (hemoptysis)
- Shortness of breath
- Discomfort during breathing
- Chest pain
- Symptoms of pneumonia (fever and a mucus-producing cough)
- Discomfort during swallowing
- Weight loss and poor appetite
- Other symptoms, if cancer has spread to the brain, bones or elsewhere
Your doctor may suspect lung cancer based on your symptoms and your history of smoking. To look for further evidence of cancer, your doctor will perform a thorough physical examination with special attention to your lungs and chest. Your doctor then will order radiologic studies such as chest x-rays and possibly a computed tomography (CT) scan to see any masses better. If cancer is suspected, tests will be done to diagnose the specific type of lung cancer and its extent of spread. These tests may include:
- Sputum sample — In this test, coughed-up mucus is checked in the laboratory for the presence of cancer cells.
- biopsy — In this test, a sample of abnormal lung tissue is removed from the body and taken to the laboratory, where it can be examined under a microscope for signs of cancer. If the biopsy specimen shows cancerous cells, the microscopic appearance of these cells will establish the type of lung cancer (small-cell or nonsmall-cell). Although this test often can be done using bronchoscopy, surgery is sometimes necessary to expose the suspicious lung area.
- Bronchoscopy — In this procedure, a tubelike instrument is passed into the lungs through the airways. The goal is to inspect the inside of the lungs directly for cancerous areas and to obtain a biopsy sample.
- Mediastinoscopy — In this procedure, a tubelike instrument is used to biopsy lymph nodes or any masses seen between the lungs (the mediastinum). A biopsy obtained this way can be used to make a diagnosis of the type of lung cancer and check for cancer spread (metastasis) to lymph nodes.
- Fine-needle aspiration — In this procedure, a fine-gauge, sterile needle is guided by CT into a suspicious area of the lungs or pleura. The needle removes a small sample of tissue for laboratory examination.
- Thoracentesis — This procedure is used when lung cancer has produced an abnormal accumulation of fluid in the chest called a pleural effusion. A sterile needle is used to withdraw a sample of the abnormal fluid for examination in the laboratory.
- Video-assisted thoracoscopic surgery (VATS) — This is a new technique to surgically biopsy abnormal lung tissue on the edges of the lung. It is less invasive than traditional methods of surgery.
- CT scans and bone scans — These scans will check for lung cancer metastases to the brain, liver, bones and elsewhere.
Once it develops, lung cancer will continue to grow and spread until it is treated.
To reduce your risk of lung cancer, you can:
- Avoid cigarette smoking — If you already smoke, ask your doctor about proven ways to help you quit.
- Avoid passive (secondhand) smoke — Choose smoke-free areas of restaurants and hotels. Also, ask house guests to smoke outdoors, especially if there are children in the home.
- Reduce exposure to asbestos — Because there is no safe level of asbestos exposure, any asbestos exposure is too much. Check your home for areas of exposed asbestos-containing insulation or other areas of deteriorating asbestos, especially if you have an older home. These areas must be removed or safely sealed off professionally. Workers who deal with asbestos-containing materials routinely should use approved measures to limit their exposure and to keep from bringing asbestos dust home on their clothing.
After lung cancer has been diagnosed, the type of treatment depends on the type of cancer and how much the tumor has spread (the stage).
NonSmall-Cell Lung Cancer
Stages of nonsmall-cell lung cancer are categorized by size and how far the tumor has spread. Stages I through III are further divided into “A” and “B” categories.
- Stage I tumors are small and have not invaded the surrounding tissue or organs.
- Stage II and III tumors have invaded surrounding tissue and/or organs and have spread to lymph nodes.
- Stage IV tumors have spread outside the chest area.
Surgery is the primary treatment for all nonsmall-cell lung cancers. Surgical options include removal of only a small part of the lung (wedge resection), removal of one lobe of the lung (lobectomy), or removal of the entire lung (pneumonectomy). Radiation therapy and chemotherapy (the use of strong medications) may be combined with surgery to help prevent cancer from returning.
People with serious medical problems that make it difficult for them to withstand surgery may receive radiation therapy to shrink the tumor or a combination of radiation and chemotherapy.
When there is significant tumor spread, chemotherapy drugs may be recommended to slow down cancer growth even if it cannot provide a cure. Chemotherapy has been shown to decrease symptoms and prolong life in advanced cases of lung cancer. Radiation therapy also may be recommended to relieve symptoms.
Small-Cell Lung Cancer
The stages for small-cell lung cancer are:
- Limited stage — Cancer involves only one lung and its nearby lymph nodes.
- Extensive stage — Cancer has spread outside the lung to other areas of the chest or to distant organs.
The treatment of small-cell lung cancer depends on its stage:
- Limited stage — Treatments include various combinations of chemotherapy, radiation and, rarely, surgery, with or without radiation to the brain to prevent cancer spread, called prophylactic cranial radiation.
- Extensive stage — Treatments include chemotherapy, with or without prophylactic cranial irradiation, or radiation treatments to areas of existing metastases in the brain, spine or other bones.
When To Call A Professional
Call your doctor promptly if you have any of the symptoms of lung cancer, especially if you are a smoker or you have worked in an industry with high exposure to asbestos.
The prognosis depends on the type of lung cancer, its stage, and the overall health of the patient. In general, only 14 percent of patients with lung cancer survive for more than five years after diagnosis. More specifically, five-year survival rates vary according to the type of lung cancer:
- Adenocarcinoma — 17 percent
- Squamous-cell carcinoma — 15 percent
- Large-cell carcinoma — 11 percent
- Small-cell carcinoma — 5 percent
Last Edited: 11 Aug. 2005
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