Lung Cancer - malignant tumors that grow in the LUNGS. Lung CANCER may be primary (originate in the lungs) or metastatic (spread to the lungs from cancer that originates elsewhere in the body). There are two main types of lung cancer: small cell lung cancer (SCLC), which is particularly aggressive, and non-small cell lung cancer (NSCLC). Malignant mesothelioma is a specific kind of cancer that arises from asbestos exposure. Cigarette smoking causes 87 percent of lung cancer in the United States and nearly all SCLC. Other causes of lung cancer include exposure to carcinogenic (cancer-causing) substances such as radon (the second-leading cause of lung cancer) and asbestos (which, when combined with smoking, compounds the risk for lung cancer).
Doctors diagnose 175,000 people with lung cancer in the United States each year. Lung cancer is the leading cause of death from cancer among men and women alike, taking the lives of 160,000 Americans each year and accounting for 30 percent of all deaths from cancer. The five-year SURVIVAL RATE is about 14 percent, which is very low compared to many other kinds of cancer. A key reason lung cancer is so frequently fatal is that it does not show symptoms until it is quite advanced, making treatment difficult. Doctors are able to diagnose only 15 percent of lung cancers when the initial tumor remains localized (confined to a distinct site within the lung), a point in time where intervention could vastly improve the chance of survival.
Non-Small Cell Lung Cancer (NSCLC)
About 80 percent of lung cancer is NSCLC. There are three types of NSCLC:
- ADENOCARCINOMA, which arises from the mucussecreting cells in the bronchial structures
- squamous cell CARCINOMA, which arises from the epithelial cells that form the inner lining of the airways
- large cell carcinoma, which commonly originates in the bronchi and contains neither squamous cells nor adenomatous (glandular) cells
Staging and treatment protocols are the same across the types of NSCLC. The most common type of NSCLC is adenocarcinoma, which is moderately aggressive. Large cell carcinoma, which accounts for about 20 percent of NSCLC, tends to be more aggressive than other NSCLC tumors and larger and metastasized at the time of diagnosis. The least aggressive of the three types of NSCLC is squamous cell carcinoma, which most commonly occurs as a consequence of cigarette smoking. Some people have more than one type of NSCLC at the time of diagnosis.
|BASIC STAGING OF NON-SMALL CELL LUNG CANCER (NSCLC)|
|Stage||Extent of Cancer||Treatment Protocols/Options|
|stage 0||cancer cells are present only in the lining of the bronchi (carcinoma in situ)||surgery or local therapy|
|stage 1a||tumor is less than 3 centimeters (cm), does not involve a major BRONCHUS, and has not spread beyond the site of origin||surgery (lobectomy)
possible adjuvant RADIATION THERAPY
|stage 1b||tumor may be more than 3 cm, may have spread to the PLEURA, or partially blocks a bronchus but has not spread to LYMPH NODES||surgery (lobectomy)
probable adjuvant radiation therapy
|stage 2a||tumor is less than 3 cm and has spread to adjacent lymph nodes but not to the pleura or sites beyond the lung||surgery (lobectomy or pneumonectomy)
adjuvant radiation therapy
|stage 2b||tumor may be more than 3 cm, may have spread to the pleura, or partially blocks a bronchus and has spread to local lymph nodes
alternately, tumor may be of any size and involves the chest wall, mainstem bronchus within 2cm of carina, or causes atelectasis of the whole lung
|surgery (lobectomy or pneumonectomy)
adjuvant radiation therapy
possible adjuvant chemotherapy
|stage 3a||tumor may be of any size and involves the chest wall, mainstem bronchus within 2cm of carina, or causes atelectasis of the whole lung
extension to mediastinal lymph nodes
|radiation therapy and CHEMOTHERAPY in combination
|stage 3b||tumor may be of any size but there is extensive, unresectable invasion of local structures and/or distant lymph node involvement||radiation therapy and chemotherapy in combination, possibly in preparation for surgery|
|stage 4||cancer has spread to locations distant from the lung||palliative chemotherapy or radiation therapy supportive care|
|STAGING OF SMALL CELL LUNG CANCER (SCLC)|
|Stage||Extent of Cancer||Treatment Protocols/Options|
|limited||cancer is present in only one lung though may have spread to adjacent LYMPH nodes||CHEMOTHERAPY, possibly in combination with RADIATION THERAPY
possibly surgery if small, localized tumor without further involvement
possible prophylactic cranial irradiation (PCI)
|extensive||cancer is present in both LUNGS, adjacent lymph nodes, and other organs (disseminated disease)||chemotherapy
palliative measures to relieve symptoms
Small Cell Lung Cancer (SCLC)
Cigarette smoking causes nearly all SCLC. Small cell lung cancer has a characteristic appearance microscopically, sometimes described as “oat cell.” This type of lung cancer grows rapidly and often has metastasized by the time of diagnosis. The outlook (prognosis) for extensive SCLC is particularly poor, with a one-year survival rate of about 20 percent. About 70 percent of people have extensive SCLC at the time of diagnosis.
Malignant mesothelioma is a rare form of cancer that occurs mostly in people who have had exposure to asbestos, particularly those who have ASBESTOSIS (a condition of damage to the lungs resulting from asbestos exposure). Malignant mesothelioma commonly arises from the PLEURA, the membrane that covers the lung. Other mesothelial membranes in the body include the PERICARDIUM, which surrounds the HEART, and the peritoneum, which lines the abdominal cavity. Malignant mesothelioma may also arise from these membranes, though that is less common. Malignant mesothelioma often does not show symptoms until it is well advanced, invading the lungs and adjacent organs or spreading through the LYMPH vessels to sites throughout the body. Doctors diagnose about 2,000 people with malignant mesothelioma each year in the United States and stage it similarly to NSCLC.
A noncancerous form of mesothelioma, benign fibrous mesothelioma, may grow from the PLEURA to reach considerable size, compressing inward on the lung or causing PLEURAL EFFUSION. Treatment is surgery to remove the tumor, which cures the condition. Benign fibrous mesothelioma does not spread and does not return after removal, though new tumors may develop in other mesothelial membranes.
Symptoms and Diagnostic Path
Early symptoms of lung cancer are often general and do not point specifically to a pulmonary condition. These early symptoms include
- loss of APPETITE and unintended weight loss
- dizziness, confusion, and memory disturbances
- JOINT aches and BONE PAIN
- FEVER without evidence of INFECTION
As the cancer becomes more established and takes over more of the lung, symptoms are more specific. These more specific symptoms include
- persistent COUGH
- HEMOPTYSIS (coughing up bloody sputum)
- chest or back pain
- wheezing (whistling sound with exhalation)
- DYSPNEA (shortness of breath)
The diagnostic path begins with a comprehensive medical examination including chest X-RAY and diagnostic blood tests. The chest X-ray may show an abnormality that, with an appropriate history, would suggest a diagnosis of cancer. Further diagnostic procedures may include COMPUTED TOMOGRAPHY (CT) SCAN, MAGNETIC RESONANCE IMAGING (MRI), POSITRON EMISSION TOMOGRAPHY (PET) SCAN, and lung biopsy, BRONCHOALVEOLAR LAVAGE, or exploratory THORACOTOMY.
A crucial element of diagnosis and treatment planning is staging, which identifies the extent to which the cancer has spread. Doctors may perform additional diagnostic procedures to determine the lung cancer’s stage. Non-small cell lung cancer and malignant mesothelioma follow a standard cancer staging scale. Because SCLC is so extraordinarily aggressive it follows a unique staging scale that primarily defines the disease as either limited or extensive.
Treatment Options and Outlook
Treatment options and outlook vary according to the type and stage of lung cancer as well as the person’s overall health status. Recommendations regarding staging and treatment options are prone to change as more research and clinical trials are available. An important part of the approach to managing care is ensuring access to current treatment protocols that may include investigational regimens. Most treatment protocols combine different therapies for optimal effectiveness. Nutritional support during cancer treatment is important to help the body fight the cancer and heal. The available treatments for lung cancer include
- Surgery, which removes the cancerous tumor and portion of the lung that contains it, is the treatment of first choice for NSCLC that remains relatively confined. When the cancer has spread to several locations within the same lung, the surgeon may remove the entire lung (pneumonectomy). Surgery may also be appropriate for very early stage SCLC, though SCLC is rarely found when it remains in an operable stage. The key risks of surgery include bleeding, infection, and limited lung function due to removal of part of the lung. Before surgery the person undergoes evaluation to estimate the ability to function after removal (resection) of part or all of the diseased lung.
- CHEMOTHERAPY, which launches a widespread attack on cancer cells throughout the body, is usually a second-line treatment that follows surgery (except in SCLC, for which it is often the first-line treatment) and may be the primary treatment for cancers that are inoperable or have already metastasized beyond the lungs. Common side effects of chemotherapy include fatigue, MOUTH sores, temporary HAIR loss, and NAUSEA and VOMITING.
- RADIATION THERAPY targets inoperable tumors or follows surgery to eradicate any residual cancer cells after the surgeon has removed the cancer. Radiation therapy may be preventive, as in prophylactic cranial irradiation (PCI) which targets the BRAIN to lower the risk for malignant METASTASES that might form there (the brain is a common metastatic site for lung cancer). Radiation therapy also may be the first-line treatment for limited SCLC or reserved for palliative, directed therapy (such as to treat an obstruction that develops in the lung).
- Photodynamic therapy (PDT) is a technique in which the oncologist administers a light-sensitive DRUG that the cancer cells absorb and then targets the cells with a laser that generates light waves to activate the drug and kill the cells that contain it. PDT may be the primary treatment for small or inoperable tumors, particularly those located in the airways. PDT increases the SKIN’s sensitivity to the sun or other sources of ultraviolet light.
- Investigational treatments are available through clinical trials. Oncologists and thoracic surgeons are aware of what trials are ongoing for certain types of cancer or patient profiles and can suggest those that are appropriate. As well the U.S. Institutes of Health’s National Cancer Institute (NCI) maintains a current listing of cancer trials, accessible at the NCI’s Web site (www.cancer.gov/clinicaltrials). Investigational treatments in the clinical trial stage have shown promise in research studies and are undergoing testing in people. It is essential to fully understand the potential benefits (personal as well as for the treatment of lung cancer in general) and risks of any investigational treatment when considering whether to participate in a clinical trial.
|COMMON CHEMOTHERAPY DRUGS FOR TREATING LUNG CANCER|
Risk Factors and Preventive Measures
Although not all lung cancer is associated with exposure to cigarette smoke, the vast majority is. In general, were it not for cigarette smoking lung cancer would be rare. This makes lung cancer one of the most preventable forms of cancer because eliminating exposure to cigarette smoke virtually eliminates the likelihood of developing lung cancer. People who smoke are at greatest risk, though people who live in households or work in environments where they continually breathe the smoke from cigarette smokers face nearly as great of a risk. Exposure to asbestos further compounds the risk for cancer in people who smoke, making any type of lung cancer more likely as well as presenting the specific risk for malignant mesothelioma. The most effective measures for preventing lung cancer are not smoking and avoiding circumstances in which other people are smoking.
Exposure to radon, a naturally occurring gas that comes from the soil and can become concentrated within indoor areas such as homes and office buildings, is the second-leading cause of lung cancer. Radon is odorless and invisible, though radon detectors can measure its presence. The U.S. Environmental Protection Agency (EPA) has established a level of 4 picocuries per liter of air (4 pCi/L) as the maximum acceptable level. Simple ventilation measures can reduce or eliminate radon from indoor air.
See also ADENOMA-TO-CARCINOMA TRANSITION; CANCER PREVENTION; CANCER TREATMENT OPTIONS AND DECISIONS; ENVIRONMENTAL CIGARETTE SMOKE; PAIN MANAGEMENT IN CANCER; RADON EXPOSURE; SMOKING AND CARDIOVASCULAR DISEASE; SMOKING AND PULMONARY DISEASE.