Description
Lung cancer is caused by uncontrolled growth and division of abnormal cells lining the breathing tubes (airways) and other lung regions. Many other cancers of the body may migrate to the lung, particularly breast cancer, colorectal cancer and prostate cancer. However, these "metastatic" cancers are not included under the term "lung cancer" since they do not originate in the lung.
Symptoms of Disease
In many cases, the symptoms of lung cancer fail to appear until lung cancer has spread. Many of the symptoms of lung cancer are shared by other disease processes that may affect the body as well, making lung cancer detection difficult. The following symptoms and conditions may be present in those with lung cancer:
- Severe and persistent cough
- Presence of blood in sputum
- Chest, shoulder and back pain
- Chronic pneumonia or bronchitis
- Change in color and/or volume of sputum
- Shortness of breath
- Chronic fatigue
- Unexplained weight loss
- Loss of appetite
- Excessive bone and joint pain
Tumors
There are two types of lung tumors:
- Benign: non-cancerous cells or processes that do not harm the body
- Malignant: cancerous cells that invade surrounding tissue and/or migrate to other body regions (process known as metastasis)
Lung Cancer Statistics
- In 2008, researchers predict more than 200,000 new cases of lung cancer will be diagnosed, making it the second most common form of solid organ cancer in men and women.
- Lung cancer is the leading cause of cancer-related death in men and women.
- This year, more than 161,000 men and women will die from lung cancer.
Risk Factors
While scientists cannot fully explain why some people do and do not develop cancer, there are several factors that can increase the likelihood of developing lung cancer. Lifestyle choices, environmental factors and genetic make-up all contribute to one's risk of developing lung cancer.
Common risk factors for lung cancer include:
- Tobacco smoke
- Smoking tobacco is the most important risk factor for developing lung cancer Inhaling the smoke of others, or second-hand smoke, also increases one's risk of lung cancer
- Harmful chemicals within tobacco greatly damage the lungs, which can eventually lead to the onset of lung cancer; the more a person smokes, the greater his or her chances of developing lung cancer.
- Cigarette, pipe, cigar and hookah smoking all increase the risk of developing lung cancer.
- Many of the cancer-causing chemicals found in tobacco smoke are also present in marijuana.
- Although not all smokers develop lung cancer, it is impossible to predict which smokers will develop lung cancer versus those who will not.
- Radon
- Radon is an invisible, odorless, radioactive gas emitted when uranium breaks down naturally in soil and rocks can damage lung cells and eventually lead to lung cancer.
- Residents in homes built over uranium-rich soil may be at risk for high radon exposure.
- Radon testing can be done with a radon test kit or by a professional radon mitigation expert; the Environmental Protection Agency (EPA) recommends mitigation of radon when radon gas levels exceed a certain limit.
- Workplace exposure
- Some professions require high levels of daily exposure to cancer-causing chemicals such as asbestos, arsenic, radon, soot and more
- the longer the exposure to chemicals, the greater the risk of developing lung cancer.
- The risk of developing lung cancer from workplace exposure is higher for smokers.
Types of Lung Cancer
- Non-small cell lung cancer (NSCLC) is the most common form of lung cancer. A combination of surgical and medical therapy is used to treat NSCLC. There are three subtypes of NSCLC that are determined by microscopic examination of a tumor sample:
- Squamous cell carcinoma
- Common among patients with history of smoking
- Forms in central lung, near the large airways (bronchi)
Adenocarcinoma
- Forms in the outer region of lung
- May be seen in both smokers and nonsmokers
- Large-cell undifferentiated carcinoma
- Forms in any region of the lung
- Extremely aggressive cancer with poor prognosis
- Small cell lung cancer (SCLC) makes up about 10 to 15 percent of all lung cancers.
- Small cell lung cancer commonly spreads (metastasizes) to other regions of the body
Diagnosis
Because lung cancer often goes unnoticed until the cancer has invaded other regions of the body, creating new techniques capable of detecting lung cancer early are a top priority of researchers. Currently, no reliable, cost-effective screening techniques have been approved for the early detection of lung cancer.
If a person shows symptoms of lung cancer, a doctor will request blood and imaging tests (X-ray or CT scan). While blood tests can provide valuable information on abnormal blood cells and chemicals, imaging tests provide a window through which doctors seek to identify lung tumors.
Most common lung imaging tests include:
- Chest X-ray: one-dimensional snapshot of lungs used to evaluate location of tumor
- Computed Tomography (CT) scan: X-ray technique creates multidimensional view of lungs; offers more detail about the exact size and shape of tumor
- Positron Emission Topography (PET): a small amount of material is injected into body that will be absorbed by cancer cells; a technique is then used to identify regions where material was absorbed
If an imaging test identifies the presence of a tumor in the lung, cells from the tumor must be obtained and examined under a microscope to determine if it is malignant or benign.
Several techniques may be used to access cancer cells:
- Needle biopsy: thin needle used to withdraw cells or pieces of tissue from the lung tumor
- Bronchoscopy: lighted scope is inserted into lungs through nose or mouth
- Technique allows doctors to get a closer look at tumor and can collect sample cells from the lungs via a needle or small forceps
- Endobronchial ultrasound: ultrasound equipment attached to bronchoscopy tube
- Ultrasound allows doctors to more accurately target tumor for biopsy
- Endoscopic esophageal ultrasound: thin, flexible, lighted tube with ultrasound is inserted into esophagus
- Doctors can view and obtain cells from lymph nodes and other structures inside the chest
- Thoracoscopy: surgical procedure in which a thin scope is inserted through small incisions in the chest wall or back between the rib spaces
- Technique allows doctors to view the space between lungs and chest walls
- Mediastinoscopy: surgical procedure where lighted scope inserted above breast bone
- Technique allows doctors to see the upper section of the lungs and sample lymph nodes for staging of lung cancer
- Sputum cytology: cells from mucus or phlegm coughed up from lung are analyzed for presence of cancer
Treatment Options
Lung cancer is difficult to treat effectively. Tumor type, size and location determine the necessary treatment.
Surgery
Surgery is considered the first line of treatment for localized non-small cell lung cancer (NSCLC) and lung carcinoid tumors. The more aggressive the spread of cancer in the lungs, the more aggressive the surgery to remove cancer will be.
- Segmentectomy: removal of cancer and a small portion of surrounding lung tissue
- Lobectomy: removal of an entire lobe of lung
- Pneumonectomy: removal of the entire lung
Surgery is rarely used in the treatment of small cell lung cancer because of its rapid spread to surrounding tissues and lymph nodes. If, however, SCLC is caught before it spreads, surgery may be used.
Radiation
Radiation therapy fights cancer by damaging cancer cells with a powerful beam of energy typically used in combination with anti-cancer drugs and/or surgery to clear any residual cancer that has not been destroyed by other methods.
- External beam radiation: radiation from outside source is directed at location of tumors and surrounding lymph nodes
- While radiation oncologists direct the radiation at the cancer cells, some surrounding normal tissue may also be harmed by the therapy, and therefore, the dose of radiation is closely monitored by the oncologist.
- Brachytherapy: internal radiation from radioactive source (usually radioactive "seeds" or pellets) planted into lung tissue near cancer; often used in combination with external beam radiation
Chemotherapy
Chemotherapy, or medical anti-cancer drug treatment, attempts to halt uncontrolled cell division of cancer by destroying all rapidly dividing cells. Different chemotherapy drugs will be prescribed based upon the type and stage of lung cancer. Chemotherapy can be used as the first defense against lung cancer, in combination with radiation (chemoradiation) or as a follow-up to surgery (adjuvant chemotherapy).
- Although chemotherapy techniques wipe out cancer cells, many normal, rapidly dividing healthy cells are also killed by these treatments. The death of healthy cells causes undesirable side effects for cancer patients such as hair loss, mouth sores, nausea, impaired resistance to infection, bruising and more.
- To lessen the harmful side effects caused by chemotherapy, researchers are working to develop ways to tailor anti-cancer drugs that specifically target cancer cells and interfere with the chemical processes that promote cancer growth.
Lung cancer patients typically respond best to combinations of chemotherapy drugs. The most commonly diagnosed chemotherapy drugs for lung cancer are:
- Cisplatin (Platinol®)
- Carboplatin (Paraplatin®)
- Paclitaxel (Taxol®)
- Docetaxel (Taxotere®)
- Gemcitabine (Gemzar®)
- Vinorelbine (Novelbine®)
- Irinotecan (Camptosar®)
- Etoposide
- Vinblastine
Additional drugs used in combination with chemotherapy:
- Targeted drug therapy that blocks the ability of cancer cells to grow by targeting a mutated protein within the cancer cell
- Erlotinib (Tarceva®) - tyrosine kinase inhibitor that blocks the activity of the epidermal growth factor receptor (EGFR)
- Angiogenesis inhibitors: drugs that prevent tumors from accessing blood vessels, shutting tumors off from accessing nutrients and oxygen
- Bevacizumab (Avastin®): blocks vascular endothelial growth factors (VEGF), a protein that helps tumors to build blood vessels
New Scientific Developments
Although tobacco use, both primary and second-hand exposure, is the leading cause of lung cancer, approximately 25 percent of lung cancer cases are not tobacco related, resulting in 300,000 deaths each year worldwide. Scientists are working to understand what causes lung cancer in this non-tobacco exposed population.
Among patients with non-small cell lung cancer, early recurrence has been linked to methylation (gene silencing) in four genes: p16, CDH13, RASSF1A and APC. Patients with these genes were between 15 to 25 times more likely to have a recurrence, regardless of past smoking history.
Another research group in China studied 71,392 women who had never smoked and found that their risk of lung cancer was higher if they had a family history of cancer. A woman with two or more close relatives who had cancer was twice as likely to get lung cancer as a woman who did not have a family history. A family history of pancreatic cancer presented the strongest risk.
Resources
American Cancer Society. Cancer Facts & Figures. Atlanta, American Cancer Society, 2008
1-800-ACS-2345
www.cancer.org
American Society for Therapeutic Radiology and Oncology
www.rtanswers.org
Lungcancer.org
1-800-813-HOPE (4673)
www.lungcancer.org
MedLine Plus
www.nlm.nih.gov/medlineplus
1-800-4-CANCER
www.cancer.gov
Last reviewed: July 18, 2008