Lung cancer develops when cells in the lung multiply abnormally, forming a mass (tumor) that grows destructively and invades normal tissues. Cancer can start in various parts of the lung such as the large air passages (bronchi), smaller airway branches (bronchioles), or tiny air sacs (alveoli). Lung cancer is especially lethal when it spreads (metastasizes) to distant locations in the body, such as the brain, bone, and liver. Lung cancer is the most common cause of cancer death for men and women.
Common Types of Lung Cancer:
Small Cell Lung Cancer (SCLC). The term small cell refers to the appearance of the cancer cells when viewed with a microscope. Nearly all patients with SCLC are heavy smokers. SCLC is a highly aggressive cancer that metastasizes very quickly and has a poor prognosis.
Non-Small Cell Lung Cancer (NSCLC). The majority of lung cancers are classified as NSCLC. Patients with NSCLC are often managed differently than those with SCLC.
Causes and Risk Factors
Cigarette smoke contains cancer-causing agents that directly damage lung cells. Smoking is the primary cause of lung cancer; however, people who have never smoked can also develop the disease.
Risk factors for lung cancer include:
High indoor levels of radon (a radioactive gas emitted by soil)
Asbestos (a material used for insulation and fire proofing)
Family history of lung cancer
High-dose beta-carotene dietary supplements.
Patients with early lung cancer are usually asymptomatic. Symptoms of lung cancer typically start when the disease is already advanced. Symptoms include:
Cough with bloody sputum
Shortness of breath
Stridor (harsh noise while breathing in)
Loss of appetite
Sometimes lung cancers produce hormones that cause dysfunction in other organs in the body. These problems are called paraneoplastic syndromes.
Lung Cancer Screening
Asymptomatic, high-risk patients can be screened with a low-dose computed tomography scan (LDCT), an imaging test used to detect lung cancer at an early stage and reduce the chance of dying from the disease.
Most patients with lung cancer develop symptoms late in the course of the disease. When symptoms arise, several tests are performed to confirm the diagnosis.
Sputum cytology is a test that detects cancer cells in secretions from the respiratory tract.
Biopsies are usually obtained during a bronchoscopy, a procedure in which a flexible instrument with a camera is passed through the mouth and trachea into the lungs, and samples of lung tissue are removed for examination under a microscope.
When enlarged lymph nodes are present, a lymph node biopsy is performed to check for cancer.
When the membrane (pleura) surrounding the lung accumulates excess fluid (pleural effusion), a procedure called thoracentesis is performed to drain and test the fluid for cancer.
Lung Cancer Staging
When lung cancer is diagnosed, the next step is to determine the extent (stage) of the disease. Staging is based on the location of the tumor, number of lesions, involvement of lymph nodes, and presence of metastases. The lung cancer stage is determined by imaging studies, including a computed tomography (CT) of the chest and abdomen; bone scan (to detect spread to the bones); and magnetic resonance imaging (MRI) or CT of the brain.
The stage is important because it determines the type of treatment required and prognosis. Small, early-stage tumors are more effectively treated than advanced cancers, which have spread to the lymph nodes or metastasized.
Surgical resection is a procedure to cut out the portion of lung containing the tumor. Depending on the size and location of the tumor, the procedure may involve the removal of a section of lung (wedge resection), a lobe of lung (lobectomy), or the entire lung (pneumonectomy) on one side of the chest. Before surgery, a patient must undergo pulmonary function tests to determine whether the remaining lung will function adequately after the procedure.
The lung cancer stage determines whether surgery will be an effective treatment. Surgery can cure early-stage NSCLC; however, surgery is not effective for advanced lung cancer that is deemed inoperable. Surgery is rarely used in patients with SCLC because SCLC is almost always metastatic by the time it is diagnosed. Such advanced cancers are treated with chemotherapy and/or radiation.
Radiation therapy involves the administration of a high dose of radiation to destroy the cancer cells. Radiation may be used in combination with surgical resection, to eliminate any residual cancer, or in lieu of surgery for inoperable tumors.
Chemotherapy utilizes medications that destroy cancer cells. Sometimes chemotherapy is used before surgery to shrink large tumors, or chemotherapy is administered after surgery to destroy residual cancer cells. Chemotherapy is used as the primary treatment for SCLC.
Complimentary and alternative treatment: Beyond conventional medicine, a variety of therapies may be implemented to relieve problems such as pain, nausea, difficulty sleeping, and stress. Such treatments include acupuncture, yoga, massage, meditation, and hypnosis.
Prognosis: Although some lung cancers are detected early enough to be cured, most cases are diagnosed and treated at a late stage. Despite a multitude of treatment options, lung cancer remains associated with a high mortality rate.
Smoking is, by far, the main cause of lung cancer. Therefore, not smoking and avoidance of secondhand smoke will markedly reduce the risk of lung cancer.
Radon is another common cause of lung cancer. High indoor radon levels are commonly found in basements of homes and workplaces. Radon mitigation systems are available to reduce radon to a safe level.
A diet high in vegetables and fruit is strongly recommended to help prevent lung cancer, but high-dose vitamin supplements are not recommended. In fact, research shows that smokers who take high doses of beta-carotene supplements actually increase their risk of lung cancer.
Gold KA, Glisson BS, Moran C. Chapter 14. Small Cell Carcinoma of the Lungs. In: Kantarjian HM, Wolff RA, Koller CA. eds. The MD Anderson Manual of Medical Oncology, 2e. New York, NY: McGraw-Hill; 2011.
Horn L, Pao W, Johnson DH. Chapter 89. Neoplasms of the Lung. In: Longo DL, Fauci AS, Kasper DL, Hauser SL, Jameson J, Loscalzo J. eds. Harrison’s Principles of Internal Medicine, 18e. New York: McGraw-Hill; 2012.
Lung Cancer. Mayo Clinic website. http://www.mayoclinic.org/diseases-conditions/lung-cancer/basics/definition/con-20025531. Accessed June 17, 2014.
Lung Cancer. American Cancer Society website. http://www.cancer.org/cancer/lungcancer/index. Accessed June 16, 2014.
Tina is a Life Science Writer for a number of online publications, including Innerbody.com. Her expertise is in conveying complex scientific topics to diverse audiences. Tina earned her PhD in Biochemistry from the University of California, San Francisco and her BS degree in Cell Biology from U.C. Davis. In her spare time, she enjoys drawing science-related cartoons.