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Definition

Lung cancer is cancer that starts in the lungs.

The lungs are located in the chest. When you breathe, air goes through your nose, down your windpipe (trachea), and into the lungs, where it flows through tubes called bronchi. Most lung cancer begins in the cells that line these tubes.

There are two main types of lung cancer:

• Non-small cell lung cancer (NSCLC) is the most common type of lung cancer.
• Small cell lung cancer (SCLC) makes up about 20% of all lung cancer cases.

If the cancer started somewhere else in the body and spreads to the lungs, it is called metastatic cancer to the lung.

Causes

Lung cancer is the deadliest type of cancer for both men and women. Each year, more people die of lung cancer than of breast, colon, and prostate cancers combined.

Lung cancer is more common in older adults. It is rare in people under age 45.

Smoking causes most cases (around 90%) of lung cancer. The risk depends on the number of cigarettes you smoke each day and for how long you have smoked. Being around the smoke from other people (secondhand smoke) also raises your risk of lung cancer. The risk decreases with time after you stop smoking. But some people who have never smoked do develop lung cancer. There is no evidence that smoking low-tar cigarettes lowers the risk.

Research shows that smoking marijuana may help cancer cells grow. But there is no direct link between smoking marijuana and developing lung cancer.

Constant exposure to high levels of air pollution and drinking water that has a high level of arsenic can increase your risk of lung cancer. A history of radiation therapy to the lungs can also increase risk.

Working with or living near cancer-causing chemicals or materials can also increase the risk of developing lung cancer. Such chemicals include:

• Arsenic
• Asbestos
• Radon
• Chemicals such as uranium, beryllium, vinyl chloride, nickel chromates, coal products, mustard gas, chloromethyl ethers, gasoline, and diesel exhaust
• Certain alloys, paints, pigments, and preservatives
• Products using chloride and formaldehyde

Symptoms

Early lung cancer may not cause any symptoms.

Symptoms depend on the type of cancer you have, but may include:

• Chest pain
• Cough that does not go away
• Coughing up blood
• Fatigue
• Losing weight without trying
• Loss of appetite
• Shortness of breath
• Wheezing

Other symptoms that may also occur with lung cancer, often in the late stages:

• Bone pain or tenderness
• Eyelid drooping
• Facial paralysis
• Hoarseness or changing voice
• Joint pain
• Nail problems
• Shoulder pain
• Swallowing difficulty
• Swelling of the face or arms
• Weakness

These symptoms can also be due to other, less serious conditions, so it is important to talk to your health care provider.

Exams and Tests

Lung cancer is often found when an x-ray or CT scan is done for another reason.

If lung cancer is suspected, your provider will perform a physical exam and ask about your medical history. You will be asked if you smoke. If so, you'll be asked how much you smoke and for how long you have smoked. You will also be asked about other things that may have put you at risk for lung cancer, such as exposure to certain chemicals.

When listening to your chest with a stethoscope, your provider may hear fluid around your lungs. This may suggest cancer.

Tests that may be done to diagnose lung cancer or to see if it has spread include:

• Bone scan
• Chest x-ray
• Complete blood count (CBC)
• Comprehensive metabolic panel
• CT scan of the chest and abdomen
• MRI of the chest
• Positron emission tomography (PET) scan
• Sputum test to look for cancer cells
• Thoracentesis (sampling of fluid buildup around the lung)

In most cases, a piece of tissue is removed from your lungs for examination under a microscope. This is called a biopsy. There are several ways to do this:

• Bronchoscopy combined with biopsy
• CT-scan-directed needle biopsy
• Endoscopic bronchoscopy ultrasound (EBUS) with biopsy
• Mediastinoscopy with biopsy
• Open lung biopsy
• Pleural biopsy

If the biopsy shows cancer, it may be checked for certain genetic changes that may lead to specific treatment. More imaging tests are done to find out the stage of the cancer. Stage means how big the tumor is and how far it has spread. Staging helps guide treatment and follow-up and gives you an idea of what to expect.

Treatment

Treatment for lung cancer depends on the type of cancer, how advanced it is, and how healthy you are:

• Surgery to remove the tumor may be done when it has not spread beyond nearby lymph nodes.
• Chemotherapy, immunotherapy, and targeted therapy use medicines to kill cancer cells and stop new cells from growing.
• Radiation therapy uses powerful x-rays or other forms of radiation to kill cancer cells.

The above treatments may be done alone or in combination. Your provider can tell you more about the specific treatment you will receive, depending on the specific type of lung cancer and what stage it is.

Support Groups

You can ease the stress of illness by joining a cancer support group. Sharing with others who have common experiences and problems can help you not feel alone.

Outlook (Prognosis)

How well you do depends on how much the lung cancer has spread and whether the cancer cells have certain genetic changes that create target molecules in or on the cells.

When to Contact a Medical Professional

Contact your provider if you have symptoms of lung cancer, particularly if you smoke.

Prevention

If you smoke, now is the time to quit. If you are having trouble quitting, talk with your provider. There are many methods to help you quit, from support groups to prescription medicines. Also, try to avoid secondhand smoke.

If you are age 50 to 80 years and have a 20 pack-year smoking history and currently smoke or have quit within the past 15 years, ask your provider about being screened for lung cancer by low-dose CT scan of your chest.

References

American Cancer Society website. Key statistics for lung cancer. www.cancer.org/cancer/types/lung-cancer/about/key-statistics.html. Updated January 29, 2024. Accessed June 3, 2024.

American Lung Association website. Lung cancer trends brief. www.lung.org/research/trends-in-lung-disease/lung-cancer-trends-brief. Accessed June 3, 2024.

Araujo LH, Horn L, Merritt RE, Shilo K, Xu-Welliver M, Carbone DP. Cancer of the lung: non-small cell lung cancer and small cell lung cancer. In: Niederhuber JE, Armitage JO, Kastan MB, Doroshow JH, Tepper JE, eds. Abeloff's Clinical Oncology. 6th ed. Philadelphia, PA: Elsevier; 2020:chap 69.

Centers for Disease Control and Prevention website. Health problems caused by secondhand smoke. www.cdc.gov/tobacco/secondhand-smoke/health.html. Updated May 15, 2024. Accessed June 3, 2024.

National Cancer Institute website. Non-small cell lung cancer treatment (PDQ) - health professional version. www.cancer.gov/types/lung/hp/non-small-cell-lung-treatment-pdq. Updated March 8, 2024. Accessed June 3, 2024.

National Cancer Institute website. Small cell lung cancer treatment (PDQ) - health professional version. www.cancer.gov/types/lung/hp/small-cell-lung-treatment-pdq. Updated May 23, 2024. Accessed June 3, 2024.

Pastis NJ, Gonzalez AV, Silvestri GA. Lung cancer: diagnosis and staging. In: Broaddus VC, Ernst JD, King TE, et al, eds. Murray and Nadel's Textbook of Respiratory Medicine. 7th ed. Philadelphia, PA: Elsevier; 2022:chap 76.

US Preventive Services Task Force website. Final recommendation statement: Lung cancer screening. www.uspreventiveservicestaskforce.org/uspstf/recommendation/lung-cancer-screening. Released March 9, 2021. Accessed June 3, 2024.

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