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Causes
By Mayo Clinic staff
Smoking causes the majority of lung cancers — both in smokers and in people exposed to secondhand smoke. But lung cancer also occurs in people who never smoked and in those who never had prolonged exposure to secondhand smoke. In these cases, there may be no clear cause of lung cancer. Doctors have identified factors that may increase the risk.
How smoking causes lung cancer
Doctors believe smoking causes lung cancer by damaging the cells that line the lungs. When you inhale cigarette smoke, which is full of cancer-causing substances (carcinogens), changes in the lung tissue begin almost immediately. At first your body may be able to repair this damage. But with each repeated exposure, normal cells that line your lungs are increasingly damaged. Over time, the damage causes cells to act abnormally and eventually cancer may develop.
Types of lung cancer
Doctors divide lung cancer into two major types based on the appearance of lung cancer cells under the microscope. Your doctor makes treatment decisions based on which major type of lung cancer you have. The two general types of lung cancer include:
- Small cell lung cancer. Small cell lung cancer occurs almost exclusively in heavy smokers and is less common than non-small cell lung cancer.
- Non-small cell lung cancer. Non-small cell lung cancer is an umbrella term for several types of lung cancers that behave in a similar way. Non-small cell lung cancers include squamous cell carcinoma, adenocarcinoma and large cell carcinoma.
- Non-small cell lung cancer. Fort Washington, Pa.: National Comprehensive Cancer Network. http://www.nccn.org/professionals/physician_gls/PDF/nscl.pdf. Accessed Sept. 23, 2009.
- Estimated new cancer cases and deaths. American Cancer Society. http://www.cancer.org/docroot/MED/content/downloads/MED_1_1x_CFF2009_Est_Cancer_Cases_Deaths.asp. Accessed Sept. 25, 2009.
- Small cell lung cancer. Fort Washington, Pa.: National Comprehensive Cancer Network. http://www.nccn.org/professionals/physician_gls/PDF/sclc.pdf. Accessed Sept. 23, 2009.
- Johnson DH, et al. Cancer of the lung: Non-small cell lung cancer and small cell lung cancer. In: Abeloff MD, et al. Abeloff's Clinical Oncology. 4th ed. Philadelphia, Pa.: Churchill Livingstone; 2008:1307.
- What you need to know about lung cancer. National Cancer Institute. http://www.nci.nih.gov/cancertopics/wyntk/lung/allpages/print. Accessed Sept. 23, 2009.
- Lung cancer prevention (PDQ): Patient version. National Cancer Institute. http://www.nci.nih.gov/cancertopics/pdq/prevention/lung/patient/allpages/print. Accessed Sept. 23, 2009.
- Cancer of the lung and bronchus. Surveillance Epidemiology and End Results. http://seer.cancer.gov/statfacts/html/lungb.html. Accessed Sept. 25, 2009.
- Questions to ask your medical team. Lung Cancer Alliance. http://www.lungcanceralliance.org/facing/questions.html. Accessed Sept. 23, 2009.
- Lung cancer screening (PDQ): Patient version. National Cancer Institute. http://www.nci.nih.gov/cancertopics/pdq/screening/lung/patient/allpages/print. Accessed Sept. 23, 2009.
- Avastin (prescribing information). South San Francisco, Calif.: Genentech Inc.; 2009. http://www.accessdata.fda.gov/drugsatfda_docs/label/2009/125085s0168lbl.pdf. Accessed Sept. 25, 2009.
- Tarceva (prescribing information). Melville, N.Y.: OSI Pharmaceuticals Inc.; 2009. http://www.accessdata.fda.gov/drugsatfda_docs/label/2009/021743s015lbl.pdf. Accessed Sept. 25, 2009.
- Kvale PA, et al. Palliative care in lung cancer. Chest. 2007;132(suppl):368S.
- Cassileth BR, et al. Complementary therapies and integrative oncology in lung cancer. Chest. 2007:132(suppl):340S.
