Lung cancer is a type of cancer that begins in the lungs, the organs responsible for breathing. It is one of the most common types of cancer and a leading cause of cancer-related deaths worldwide.

There are two main types of lung cancer: non-small cell lung cancer (NSCLC) and small cell lung cancer (SCLC). NSCLC is the most common type, accounting for approximately 85% of all lung cancer cases, while SCLC accounts for the remaining 15%.

The most common cause of lung cancer is smoking tobacco, either through cigarettes, pipes, or cigars. Other risk factors for lung cancer include exposure to secondhand smoke, exposure to radon gas, air pollution, and occupational exposure to certain chemicals.

Symptoms of lung cancer can vary depending on the type and stage of the cancer, but may include a persistent cough, chest pain, difficulty breathing, wheezing, fatigue, and unexplained weight loss.

Treatment for lung cancer depends on the type and stage of the cancer, as well as the overall health of the patient. Options may include surgery, radiation therapy, chemotherapy, targeted therapy, immunotherapy, or a combination of these treatments.

Prevention is key when it comes to lung cancer. The most effective way to prevent lung cancer is to quit smoking or never start smoking in the first place. Avoiding exposure to secondhand smoke, testing for and mitigating radon levels in homes, and reducing exposure to air pollution and occupational chemicals can also help reduce the risk of lung cancer.

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.

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. Non-small cell lung cancers include squamous cell carcinoma, adenocarcinoma and large cell carcinoma.

There's no sure way to prevent lung cancer, but you can reduce your risk if you:

• Don't smoke. If you've never smoked, don't start. Talk to your children about not smoking so that they can understand how to avoid this major risk factor for lung cancer. Begin conversations about the dangers of smoking with your children early so that they know how to react to peer pressure.
• Stop smoking. Stop smoking now. Quitting reduces your risk of lung cancer, even if you've smoked for years. Talk to your doctor about strategies and stop-smoking aids that can help you quit. Options include nicotine replacement products, medications and support groups.
• Avoid secondhand smoke. If you live or work with a smoker, urge him or her to quit. At the very least, ask him or her to smoke outside. Avoid areas where people smoke, such as bars and restaurants, and seek out smoke-free options.
• Test your home for radon. Have the radon levels in your home checked, especially if you live in an area where radon is known to be a problem. High radon levels can be remedied to make your home safer. For information on radon testing, contact your local department of public health or a local chapter of the American Lung Association.
• Avoid carcinogens at work. Take precautions to protect yourself from exposure to toxic chemicals at work. Follow your employer's precautions. For instance, if you're given a face mask for protection, always wear it. Ask your doctor what more you can do to protect yourself at work. Your risk of lung damage from workplace carcinogens increases if you smoke.
• Eat a diet full of fruits and vegetables. Choose a healthy diet with a variety of fruits and vegetables. Food sources of vitamins and nutrients are best. Avoid taking large doses of vitamins in pill form, as they may be harmful. For instance, researchers hoping to reduce the risk of lung cancer in heavy smokers gave them beta carotene supplements. Results showed the supplements actually increased the risk of cancer in smokers.
• Exercise most days of the week. If you don't exercise regularly, start out slowly. Try to exercise most days of the week.

You and your doctor choose a cancer treatment plan based on a number of factors, such as your overall health, the type and stage of your cancer, and your preferences.

In some cases, you may choose not to undergo treatment. For instance, you may feel that the side effects of treatment will outweigh the potential benefits. When that's the case, your doctor may suggest comfort care to treat only the symptoms the cancer is causing, such as pain or shortness of breath.

Surgery

During surgery, your surgeon works to remove the lung cancer and a margin of healthy tissue. Procedures to remove lung cancer include:

• Wedge resection to remove a small section of lung that contains the tumor along with a margin of healthy tissue
• Segmental resection to remove a larger portion of lung, but not an entire lobe
• Lobectomy to remove the entire lobe of one lung
• Pneumonectomy to remove an entire lung

If you undergo surgery, your surgeon may also remove lymph nodes from your chest in order to check them for signs of cancer.

Surgery may be an option if your cancer is confined to the lungs. If you have a larger lung cancer, your doctor may recommend chemotherapy or radiation therapy before surgery in order to shrink the cancer. If there's a risk that cancer cells were left behind after surgery or that your cancer may recur, your doctor may recommend chemotherapy or radiation therapy after surgery.

Radiation therapy

Radiation therapy uses high-powered energy beams from sources such as X-rays and protons to kill cancer cells. During radiation therapy, you lie on a table while a machine moves around you, directing radiation to precise points on your body.

For people with locally advanced lung cancer, radiation may be used before surgery or after surgery. It's often combined with chemotherapy treatments. If surgery isn't an option, combined chemotherapy and radiation therapy may be your primary treatment.

For advanced lung cancers and those that have spread to other areas of the body, radiation therapy may help relieve symptoms, such as pain.

Chemotherapy

Chemotherapy uses drugs to kill cancer cells. One or more chemotherapy drugs may be given through a vein in your arm (intravenously) or taken orally. A combination of drugs usually is given in a series of treatments over a period of weeks or months, with breaks in between so that you can recover.

Chemotherapy is often used after surgery to kill any cancer cells that may remain. It can be used alone or combined with radiation therapy. Chemotherapy may also be used before surgery to shrink cancers and make them easier to remove.

In people with advanced lung cancer, chemotherapy can be used to relieve pain and other symptoms.

Stereotactic body radiotherapy

Stereotactic body radiotherapy, also known as radiosurgery, is an intense radiation treatment that aims many beams of radiation from many angles at the cancer. Stereotactic body radiotherapy treatment is typically completed in one or a few treatments.

Stereotactic body radiotherapy may be an option for people with small lung cancers who can't undergo surgery. It may also be used to treat lung cancer that spreads to other parts of the body, including the brain.

Targeted drug therapy

Targeted drug treatments focus on specific abnormalities present within cancer cells. By blocking these abnormalities, targeted drug treatments can cause cancer cells to die.

Many targeted therapy drugs are used to treat lung cancer, though most are reserved for people with advanced or recurrent cancer.

Some targeted therapies only work in people whose cancer cells have certain genetic mutations. Your cancer cells may be tested in a laboratory to see if these drugs might help you.

Immunotherapy

Immunotherapy uses your immune system to fight cancer. Your body's disease-fighting immune system may not attack your cancer because the cancer cells produce proteins that help them hide from the immune system cells. Immunotherapy works by interfering with that process.

Immunotherapy treatments are generally reserved for people with locally advanced lung cancers and cancers that have spread to other parts of the body.

Palliative care

People with lung cancer often experience signs and symptoms of the cancer, as well as side effects of treatment. Supportive care, also known as palliative care, is a specialty area of medicine that involves working with a doctor to minimize your signs and symptoms.

Your doctor may recommend that you meet with a palliative care team soon after your diagnosis to ensure that you're comfortable during and after your cancer treatment.

In one study, people with advanced non-small cell lung cancer who began receiving supportive care soon after their diagnosis lived longer than those who continued with treatments, such as chemotherapy and radiation. Those receiving supportive care reported improved mood and quality of life. They survived, on average, almost three months longer than did those receiving standard care.