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Lung Cancer

(Lung Carcinoma)


Robert L. Keith

, MD, Division of Pulmonary Sciences and Critical Care Medicine, University of Colorado School of Medicine

Reviewed/Revised Dec 2022 | Modified Dec 2023
Topic Resources

Lung cancer is the leading cause of cancer death in both men and women. About 85% of cases are related to cigarette smoking.

  • One common symptom is a persistent cough or a change in the character of a chronic cough.

  • Chest x-rays can detect most lung cancers, but other additional imaging tests and biopsies are needed to confirm the diagnosis.

  • Surgery, chemotherapy, targeted agents, immunotherapy, and radiation therapy may all be used to treat lung cancer.

In 2022, the American Cancer Society estimated that 236,740 new cases of lung cancer will be diagnosed in the United States (118,830 in women and 117,910 in men), and 130,180 people will die from the disease. The incidence of lung cancer has been declining in men over the past 3 decades and has started to decline in women. These trends reflect a decrease in the number of smokers over the last 30 years.

Primary lung cancer is cancer that originates from lung cells. Primary lung cancer can start in the airways that branch off the trachea to supply the lungs (the bronchi) or in the small air sacs of the lung (the alveoli).

Metastatic lung cancer is cancer that has spread to the lung from other parts of the body (most commonly from the breasts, colon, prostate, kidneys, thyroid gland, stomach, cervix, rectum, testes, bones, or skin).

There are two main categories of primary lung cancer:

  • Non–small cell lung cancer: About 85% of lung cancers are in this category. This cancer grows more slowly than small cell lung cancer. Nevertheless, by the time about 40% of people are diagnosed, the cancer has spread to other parts of the body outside of the chest. The most common types of non–small cell lung cancer are squamous cell carcinoma, adenocarcinoma, and large cell carcinoma.

  • Small cell lung cancer: Sometimes called oat cell carcinoma, this cancer accounts for about 15% of all lung cancers. It is very aggressive and spreads quickly. By the time that most people are diagnosed, the cancer has spread to other parts of the body.

Rare lung cancers include

Causes of Lung Cancer

Cigarette smoking is the leading cause of lung cancer, accounting for about 85% of all lung cancer cases. The risk of developing lung cancer varies by both the number of cigarettes smoked and the number of years of smoking. Still, some heavy smokers do not develop lung cancer. In people who quit smoking, the risk of developing lung cancer decreases, but former smokers continue to have a higher risk of developing lung cancer than people who never smoked.

About 15 to 20% of people who develop lung cancer have never smoked or have smoked only minimally. In these people, the reason why they develop lung cancer is unknown, but certain genetic mutations may be responsible.

Other possible risk factors include

  • Air pollution

  • Exposure to cigar smoke

  • Exposure to secondhand cigarette smoke

  • Exposure to carcinogens such as asbestos, radiation, radon, arsenic, chromates, nickel, chloromethyl ethers, polycyclic aromatic hydrocarbons, mustard gas, or coke-oven emissions that are encountered or breathed in at work

  • Exclusively using open fires for cooking and heating

The risk of contracting lung cancer is greater in people who are exposed to these substances and who also smoke cigarettes.

The risk of lung cancer related to electronic nicotine delivery systems such as e-cigarettes remains to be determined, although doctors think that the substances created by burning tobacco are more likely to be the cause of cancer than nicotine itself.

It is unknown whether marijuana smoking increases the risk of lung cancer.

Whether and how much an exposure to household radon increases risk of lung cancer is controversial. However, many reports suggest that radon exposure is a risk factor for lung cancer.

In rare incidences, lung cancers, especially adenocarcinoma and bronchioloalveolar cell carcinoma (a type of adenocarcinoma also known as adenocarcinoma in situ), develop in people whose lungs have been scarred by other lung disorders, such as tuberculosis. Tuberculosis (TB) Tuberculosis is a chronic contagious infection caused by the airborne bacteria Mycobacterium tuberculosis. It usually affects the lungs, but almost any organ can be involved. Tuberculosis... read more Tuberculosis (TB) Also, smokers who take beta-carotene supplements may have an increased risk of developing lung cancer.

Did You Know...

  • Although smoking causes most cases, people who have never smoked may still get lung cancer.

Symptoms of Lung Cancer

The symptoms of lung cancer depend on its type, its location, and the way it spreads within the lungs, to areas near the lungs, or elsewhere in the body. Some people have no symptoms at the time of diagnosis.

One of the more common symptoms is a persistent cough or, in people who have a chronic cough, a change in the character of the cough. Some people cough up blood or sputum streaked with blood (hemoptysis Coughing Up Blood Coughing up blood from the respiratory tract is called hemoptysis. The amount of blood produced can vary from a few streaks of blood mixed with normal sputum to large amounts of pure blood.... read more ). Rarely, lung cancer grows into an underlying blood vessel and causes severe bleeding.

Additional nonspecific symptoms of lung cancer include loss of appetite, weight loss, fatigue, chest pain, and weakness.

Complications of lung cancer

Lung cancer may narrow the airway, causing wheezing. If a tumor blocks an airway, part of the lung that the airway supplies may collapse, a condition called atelectasis Atelectasis Atelectasis is a condition in which all or part of a lung becomes airless and collapses. Blockage of the bronchial tubes is a common cause of atelectasis. Shortness of breath can develop if... read more . Other consequences of a blocked airway are shortness of breath and pneumonia, which may result in coughing, fever, and chest pain.

If the tumor grows into the chest wall, it may cause persistent, unrelenting chest pain. Fluid containing cancerous cells can accumulate in the space between the lung and the chest wall (a condition referred to as malignant pleural effusion Pleural Effusion Pleural effusion is the abnormal accumulation of fluid in the pleural space (the area between the two layers of the thin membrane that covers the lungs). Fluid can accumulate in the pleural... read more Pleural Effusion ). Large amounts of fluid can lead to shortness of breath and chest pain. If the cancer spreads throughout the lungs, the levels of oxygen in the blood become low, causing shortness of breath and eventually enlargement of the right side of the heart and possible heart failure (a disorder called cor pulmonale Cor Pulmonale Cor pulmonale is enlargement and thickening of the ventricle on the right side of the heart resulting from an underlying lung disorder that causes pulmonary hypertension (high pressures in the... read more ).

Lung cancer may grow into certain nerves in the neck, causing a droopy eyelid, small pupil, and reduced perspiration on one side of the face—together these symptoms are called Horner syndrome Horner Syndrome Horner syndrome affects one side of the face, causing the eyelid to droop, the pupil to become small (constricted), and sweating to decrease. The cause is disruption of the nerve fibers that... read more Horner Syndrome .

Cancers at the top of the lung may grow into the nerves that supply the arm, making the arm or shoulder painful, numb, and weak. Tumors in this location are often called Pancoast tumors. When the tumor grows into nerves in the center of the chest, the nerve to the voice box may become damaged, making the voice hoarse, and the nerve to the diaphragm may become damaged, causing shortness of breath and low blood oxygen levels.

Lung cancer may grow into or near the esophagus, leading to difficulty swallowing or pain with swallowing.

Lung cancer may grow into the heart or in the midchest (mediastinal) region, causing abnormal heart rhythms, blockage of blood flow into the heart, or fluid in the sac surrounding the heart (pericardial sac).

The cancer may grow into or compress one of the large veins in the chest (the superior vena cava). This condition is called superior vena cava syndrome. Blockage of the superior vena cava causes blood to back up in other veins of the upper body. The veins in the chest wall enlarge. The face, neck, and upper chest wall—including the breasts—can swell, causing pain, and become flushed. The condition can also cause shortness of breath, headache, distorted vision, dizziness, and drowsiness. These symptoms usually worsen when the person bends forward or lies down.

Lung cancer may also spread through the bloodstream to other parts of the body, most commonly the liver, brain, adrenal glands, spinal cord, or bones. The spread of lung cancer may occur early in the course of disease, especially with small cell lung cancer. Symptoms—such as headache, confusion, seizures, and bone pain—may develop before any lung problems become evident, making an early diagnosis more complicated.

Paraneoplastic syndromes Paraneoplastic Syndromes Paraneoplastic (associated with cancer—see also Overview of Cancer) syndromes occur when a cancer causes unusual symptoms due to substances that circulate in the bloodstream. These substances... read more consist of effects that are caused by the cancer but occur far from the cancer itself, such as in nerves and muscles. These syndromes are not related to the size or location of the lung cancer and do not indicate that the cancer has spread outside the chest. These syndromes are caused by substances secreted by the cancer (such as hormones, cytokines, and various other proteins). Common paraneoplastic effects of lung cancer include

Diagnosis of Lung Cancer

  • Imaging

  • Microscopic examination of tumor cells

  • Genetic testing of the tumor

  • Staging

Doctors explore the possibility of lung cancer when a person, especially a smoker, has a persistent or worsening cough, other lung symptoms (such as shortness of breath or coughed-up sputum tinged with blood), or weight loss. Lung cancer also is a concern if people appear to have had pneumonia but their x-ray does not clear up after a course of antibiotics.


Chest x-ray X-Rays of the Chest X-rays are a type of medical imaging that use very low-dose radiation waves to take pictures of bones and soft tissues. Chest x-rays are sometimes used in people who may have a heart disorder... read more X-Rays of the Chest is usually the first test. Chest x-ray can detect most lung tumors, although it may miss small ones. Sometimes an abnormality detected on a chest x-ray done for other reasons (such as before surgery) provides doctors with the first clue, although an abnormality is not proof of cancer.

Computed tomography Computed Tomography (CT) of the Heart Computed tomography (CT) is a type of medical imaging that combines a series of x-rays to create cross-sectional, detailed images of internal structures, including the heart. CT may be used... read more (CT) may be done next. CT can show characteristic patterns that help doctors make the diagnosis. They also can show small tumors that are not visible on chest x-rays and reveal whether the lymph nodes inside the chest are enlarged.

Newer techniques, such as positron emission tomography Positron Emission Tomography (PET) of the Heart Positron emission tomography (PET) is a type of medical imaging called radionuclide scanning. By detecting radiation after a radioactive material is administered, PET creates images that can... read more (PET) and PET-CT scanning, which combine the PET and CT technology in one machine, are increasingly used to evaluate people with suspected cancer and often is used to help detect disease that has spread outside the chest. Magnetic resonance imaging (MRI) can also be used if the CT or PET-CT scans do not give doctors sufficient information.

Microscopic examination

A microscopic examination of lung tissue from the area that may be cancerous is usually needed to confirm the diagnosis. Occasionally, a sample of coughed-up sputum can provide enough material for an examination (called sputum cytology). If the cancer has caused a malignant pleural effusion, removing and testing the pleural fluid may be enough. Usually, however, doctors need to obtain a sample of tissue (biopsy) directly from the tumor. One common way to obtain the tissue sample is with bronchoscopy Bronchoscopy Bronchoscopy is a direct visual examination of the voice box (larynx) and airways through a viewing tube (a bronchoscope). A bronchoscope, a thin viewing tube with a light, has a camera at the... read more Bronchoscopy . The person’s airway is directly observed using a flexible scope and samples of the tumor can be obtained. Bronchoscopes that incorporate ultrasonographic devices can find and biopsy tissue that cannot be seen with a regular bronchoscope, including lymph nodes in the middle of the chest (mediastinum). This helps to stage the disease and will guide treatment.

If the cancer is too far away from the major airways to be reached with a bronchoscope, doctors can usually obtain a specimen by inserting an instrument through the skin. This procedure is called a percutaneous biopsy. Sometimes, a specimen can only be obtained by a surgical procedure called a thoracotomy Thoracotomy Thoracotomy is an operation in which the chest wall is opened to view the internal chest organs, to obtain samples of tissue for laboratory examination, and to treat disorders of the lungs,... read more . Doctors may also do a mediastinoscopy, in which they take and examine samples of enlarged lymph nodes (a biopsy) from the center of the chest to determine if inflammation or cancer is responsible for the enlargement.

Genetic testing

Doctors do genetic tests on the tissue sample to see whether the person's cancer is caused by a mutation that can be treated with drugs that target the mutation's effects.


Once cancer has been identified under the microscope, doctors usually do tests to determine whether it has spread. A PET-CT scan and head imaging (brain CT or MRI) may be done to determine if lung cancer has spread, especially to the liver, adrenal glands, or brain. If a PET-CT is not available, CT scans of the chest, abdomen, and pelvis and a bone scan are done. A bone scan may show that cancer has spread to the bones.

Cancers are categorized based on

  • How large the tumor is

  • Whether it has spread to nearby lymph nodes

  • Whether it has spread to distant organs

The different categories are used to determine the stage of the cancer Staging Cancer Cancer is suspected based on a person's symptoms, the results of a physical examination, and sometimes the results of screening tests. Occasionally, x-rays obtained for other reasons, such as... read more . The stage of a cancer suggests the most appropriate treatment and enables doctors to estimate the person’s prognosis.

Screening for lung cancer

Screening tests are tests done in high risk people without symptoms to look for evidence of a disease when it is at an early stage. For lung cancer, screening tests include low dose CT scans..

Screening of all people (that is, whether or not they have risk factors) has not been shown to decrease risk of death from lung cancer and thus is not recommended. Tests can be expensive and cause people undue worry if they produce false-positive results that incorrectly imply that a cancer is present. The opposite is also true. A screening test can give a negative result when a cancer really does exist.

Screening of high-risk people, however, is recommended. Doctors try to accurately determine a person’s risk for a particular cancer before screening tests Screening for Cancer Screening tests are used to detect the possibility that a disease is present before symptoms occur. Screening tests usually are not definitive. Results are confirmed or disproved with... read more are done. People who may benefit from screening for lung cancer include middle-aged and older people who smoke heavily or have smoked for many years. Current guidelines recommend screening for people age 50 to 80 who have a cigarette smoking history of over 20 pack-years (calculated by multiplying years smoked by number of packs per day) who still smoke or have quit within the last 15 years. Yearly CT with a technique that uses lower-than-normal amounts of radiation seems to find enough cancers that can be cured to save lives. However, screening chest x-rays and sputum examinations in these high-risk people are not recommended.

Prevention of Lung Cancer

Prevention of lung cancer includes quitting smoking Smoking and Other Tobacco Use Tobacco use is a major individual and public health problem. Using tobacco is harmful to almost every organ in the body. Tobacco is used because of the effects of nicotine. Nicotine is highly... read more and avoiding exposure to potentially cancer-causing substances. People may want to take measures to reduce radon in their homes. Other potential prevention agents should only be used as part of a clinical trial.

Treatment of Lung Cancer

  • Surgery

  • Radiation therapy

  • Chemotherapy

  • Targeted therapies

Doctors use various treatments for both small cell and non–small cell lung cancer. Surgery, chemotherapy, and radiation therapy can be used individually or in combination. The precise combination of treatments depends on the

  • Type of cancer

  • Location of the cancer

  • Severity of the cancer

  • Degree to which the cancer has spread

  • Person's overall health

For example, in some people with advanced non–small cell lung cancer, treatment includes chemotherapy and radiation therapy before, after, or instead of surgical removal.

Surgery for lung cancer

Surgery is the treatment of choice for non–small cell lung cancer that has not spread beyond the lung (early-stage disease). In general, surgery is not used for early-stage small cell lung cancer, because this aggressive cancer that has often spread beyond the lungs at the time of diagnosis and therefore is treated with chemotherapy and radiation therapy. Surgery for non-small cell lung cancer may not be possible if the cancer has spread beyond the lungs, if the cancer is too close to the windpipe, or if the person has other serious conditions (such as severe heart or lung disease).

Before surgery, doctors do pulmonary function tests Pulmonary Function Testing (PFT) Pulmonary function tests measure the lungs' capacity to hold air, to move air in and out, and to absorb oxygen. Pulmonary function tests are better at detecting the general type and severity... read more Pulmonary Function Testing (PFT) to determine whether the amount of lung remaining after surgery will be able to provide enough oxygen and breathing function. If the test results indicate that removing the cancerous part of the lung will result in inadequate lung function, surgery is not possible. The amount of lung to be removed is decided by the surgeon, with the amount varying from a small part of a lung segment to an entire lung.

Although non–small cell lung cancers can be removed surgically, removal does not always result in a cure. Supplemental (adjuvant) chemotherapy after surgery can help increase the survival rate and is done for all but the smallest cancers. Sometimes chemotherapy is given before surgery (called neoadjuvant therapy) to help shrink the tumor before surgery is done.

Occasionally, cancer that begins elsewhere (for example, in the colon) and spreads to the lungs is removed from the lungs after being removed at the source. This procedure is recommended rarely, and tests must show that the cancer has not spread to any site outside of the lungs.

Radiation therapy for lung cancer

Radiation therapy is used in both non–small cell and small cell lung cancers. It may be given to people who do not want to undergo surgery, who cannot undergo surgery because they have another condition (such as severe coronary artery disease), or whose cancer has spread to nearby structures, such as the lymph nodes. Although radiation therapy is used to treat the cancer, in some people, it may only partially shrink the cancer or slow its growth. Combining chemotherapy with radiation therapy improves survival in these people.

Some people with small cell lung cancer who have been responding well to chemotherapy may benefit from radiation therapy to the head to prevent spread of cancer to the brain. If the cancer has already spread to the brain, radiation therapy of the brain is commonly used to reduce symptoms such as headache, confusion, and seizures.

Radiation therapy is also useful for controlling the complications of lung cancer, such as coughing up of blood, bone pain, superior vena cava syndrome, and spinal cord compression.

Chemotherapy for lung cancer

Chemotherapy is used in both non–small cell and small cell lung cancers. In small cell lung cancer, chemotherapy, sometimes coupled with radiation therapy, is the main treatment. This approach is preferred because small cell lung cancer is aggressive and has often spread to distant parts of the body by the time of diagnosis. Chemotherapy can prolong survival in people who have advanced disease. Without treatment, the median survival is only 6 to 12 weeks.

In non–small cell lung cancer, chemotherapy usually also prolongs survival and treats symptoms. In people with non–small cell lung cancer that has spread to other parts of the body, the median survival increases to 9 months with treatment. Targeted therapies may also improve cancer patient survival.

Targeted therapies for lung cancer

Some people with non–small cell lung cancer survive significantly longer when treated with chemotherapy, radiation therapy, or some of the targeted therapies. Targeted therapies include drugs, such as biologic agents that specifically target lung tumors. Studies have identified proteins within cancer cells and the blood vessels that nourish the cancer cells. These proteins may be involved in regulating and promoting cancer growth and metastasis. Drugs have been designed to specifically affect the abnormal protein's effects and potentially kill the cancer cells or inhibit their growth. Drugs that target such abnormalities include bevacizumab, gefitinib, erlotinib, crizotinib, vemurafenib, and dabrafenib.

Immunotherapy drugs, which include nivolumab, pembrolizumab, durvalumab, ipilimumab, and atezolizumab, enable a person's own immune system to fight the cancer. These drugs may be used instead of the usual chemotherapy drugs, in combination with them, or after the conventional chemotherapy drugs have been tried and have not worked.

Laser and ablation therapy for lung cancer

Laser therapy, in which a laser is used to remove or reduce the size of lung tumors, is sometimes used. A high-energy current (radiofrequency ablation) or cold (cryoablation) can sometimes be used to destroy tumor cells in people who have small tumors or are unable to undergo surgery.

Other treatments

Other treatments are often needed for people who have lung cancer. Many such treatments, called palliative treatments, aim to relieve symptoms and improve quality of life rather than cure cancer.

Because many people who have lung cancer have a substantial decrease in lung function whether or not they undergo treatment, oxygen therapy Oxygen Therapy Oxygen therapy is a treatment that delivers extra oxygen to the lungs when the level of oxygen in the blood is too low. Oxygen is a gas that makes up about 21% of the air we breathe. The lungs... read more Oxygen Therapy and bronchodilators (drugs that widen the airways) may aid breathing.

Pain often requires treatment. Opioids are often used to relieve pain but can cause side effects, such as constipation, that also require treatment.

Prognosis for Lung Cancer

Lung cancer has a poor prognosis. On average, people with untreated advanced non–small cell lung cancer survive 6 months. Even with treatment, people with extensive small cell lung cancer or advanced non–small cell lung cancer do especially poorly, with a 5-year survival rate of less than 1%. Early diagnosis improves survival. People with early non–small cell lung cancer have a 5-year survival of 50 to 70%. However, people who are treated definitively for an earlier stage lung cancer and survive but continue to smoke are at high risk of developing another lung cancer.

Survivors must have regular checkups, including periodic chest x-rays and CT scans to ensure that the cancer has not returned. Usually, if the cancer returns, it occurs within the first 2 years. However, frequent monitoring is recommended for 5 years after lung cancer treatment, and then people are monitored yearly for the rest of their lives.

Because many people die of lung cancer, planning for terminal care Choices to Make Before Death Seriously ill people and their families may feel swept along by the fatal illness and the various treatments, as if they have no control over the events. Some people seem to prefer this sense... read more is usually necessary. Advances in end-of-life care, particularly the recognition that anxiety and pain are common in people with incurable lung cancer and that these symptoms can be relieved by appropriate drugs, have led to an increasing number of people being able to die comfortably at home, with or without hospice services.

More Information

The following English language resources provide information and support for patients and their caregivers. THE MANUAL is not responsible for the content of these resources.

Drugs Mentioned In This Article

Generic Name Select Brand Names
Alymsys, Avastin, MVASI, Zirabev
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