Lung cancer is a type of cancer that begins in the lungs. The lungs are two organs in the chest that take in oxygen when we inhale and release carbon dioxide when we  exhale.
People who smoke have the greatest risk of lung cancer. The risk of lung cancer increases with the length of time and number of cigarettes smoked.

Symptoms

In its earliest stages, lung cancer typically doesn't cause signs and symptoms. Signs and symptoms usually don't occur until the disease has advanced and progressed.
Signs and symptoms of lung cancer may include:

  • A new cough that doesn't go away
  • Changes in a chronic cough or "smoker's cough"
  • Coughing up blood, even a small amount
  • Shortness of breath
  • Chest pain
  • Wheezing
  • Hoarseness
  • Losing weight without trying
  • Bone pain
  • Headache

Most often these symptoms are not due to cancer. Other health problems can cause some of these symptoms. Anyone with such symptoms should see a doctor to be diagnosed and treated as early as possible

Risk Factors

Studies have found the following risk factors for lung cancer:

  • Tobacco smoke: Tobacco smoke causes most cases of lung cancer. It's by far the most important risk factor for lung cancer. Harmful substances in smoke damage lung cells. That's why smoking cigarettes, pipes, or cigars can cause lung cancer and why secondhand smoke can cause lung cancer in nonsmokers. The more a person is exposed to smoke, the greater the risk of lung cancer.
  • Radon: Radon is a radioactive gas that you cannot see, smell, or taste. It forms in soil and rocks. People who work in mines may be exposed to radon. In some parts of the country, radon is found in houses. Radon damages lung cells, and people exposed to radon are at increased risk of lung cancer. The risk of lung cancer from radon is even higher for smokers.
  • Asbestos and other substances: People who have certain jobs (such as those who work in the construction and chemical industries) have an increased risk of lung cancer. Exposure to asbestos, arsenic, chromium, nickel, soot, tar, and other substances can cause lung cancer. The risk is highest for those with years of exposure. The risk of lung cancer from these substances is even higher for smokers.
  • Air pollution: Air pollution may slightly increase the risk of lung cancer. The risk from air pollution is higher for smokers.
  • Family history of lung cancer: People with a father, mother, brother, or sister who had lung cancer may be at slightly increased risk of the disease, even if they don't smoke.
  • Personal history of lung cancer: People who have had lung cancer are at increased risk of developing a second lung tumor.
  • Age over 65: Most people are older than 65 years when diagnosed with lung cancer.

Diagnosis

Tests for lung cancer include:

  • Physical exam: Your doctor checks for general signs of health, listens to your breathing, and checks for fluid in the lungs. Your doctor may feel for swollen lymph nodes and a swollen liver.
  • Chest x-ray: X-ray pictures of your chest may show tumors or abnormal fluid.
  • CT scan: Doctors often use CT scans to take pictures of tissue inside the chest. An x-ray machine linked to a computer takes several pictures. For a spiral CT scan, the CT scanner rotates around you as you lie on a table. The table passes through the center of the scanner. The pictures may show a tumor, abnormal fluid, or swollen lymph nodes.

Diagnosing Different Types of Lung Cancer

The only sure way to know if lung cancer is present is for a pathologist to check samples of cells or tissue. The pathologist studies the sample under a microscope and performs other tests. There are many ways to collect samples. Doctors order one or more of the following tests to collect samples:

  • Sputum cytology: Thick fluid (sputum) is coughed up from the lungs. The lab checks samples of sputum for cancer cells.
  • Thoracentesis: The doctor uses a long needle to remove fluid (pleural fluid) from the chest. The lab checks the fluid for cancer cells.
  • Bronchoscopy: The doctor inserts a thin, lighted tube (a bronchoscope) through the nose or mouth into the lung. This allows an exam of the lungs and the air passages that lead to them. The doctor may take a sample of cells with a needle, brush, or other tool. The doctor also may wash the area with water to collect cells in the water.
  • Fine-needle aspiration: The doctor uses a thin needle to remove tissue or fluid from the lung or lymph node. Sometimes the doctor uses a CT scan or other imaging method to guide the needle to a lung tumor or lymph node.
  • Thoracoscopy: The surgeon makes several small incisions in your chest and back. The surgeon looks at the lungs and nearby tissues with a thin, lighted tube. If an abnormal area is seen, a biopsy to check for cancer cells may be needed.
  • Thoracotomy: The surgeon opens the chest with a long incision. Lymph nodes and other tissue may be removed.
  • Mediastinoscopy: The surgeon makes an incision at the top of the breastbone. A thin, lighted tube is used to see inside the chest. The surgeon may take tissue and lymph node samples

Types of Lung Cancer

The pathologist checks the sputum, pleural fluid, tissue, or other samples for cancer cells. If cancer is found, the pathologist reports the type. The types of lung cancer are treated differently. The most common types are named for how the lung cancer cells look under a microscope:

  • Small cell lung cancer: About 13 percent of lung cancers are small cell lung cancers. This type tends to spread quickly
  • Non-small cell lung cancer: Most lung cancers (about 87 percent) are non-small cell lung cancers. This type spreads more slowly than small cell lung cancer

Stages of Small Cell Lung Cancer

Doctors describe small cell lung cancer using two stages:

  • Limited stage: Cancer is found only in one lung and its nearby tissues.
  • Extensive stage: Cancer is found in tissues of the chest outside of the lung in which it began. Or cancer is found in distant organs.

The treatment options are different for limited and extensive stage small cell lung cancer.

Stages of Non-Small Cell Lung Cancer

Doctors describe non-small cell lung cancer based on the size of the lung tumor and whether cancer has spread to the lymph nodes or other tissues:

Occult Stage

Lung cancer cells are found in sputum or in a sample of water collected during bronchoscopy, but a tumor cannot be seen in the lung.

Stage 0

Cancer cells are found only in the innermost lining of the lung. The tumor has not grown through this lining. A Stage 0 tumor is also called carcinoma in situ. The tumor is not an invasive cancer.

Stage IA

The lung tumor is an invasive cancer. It has grown through the innermost lining of the lung into deeper lung tissue. The tumor is no more than 3 centimeters across (less than 1 ¼ inches). It is surrounded by normal tissue and the tumor does not invade the bronchus. Cancer cells are not found in nearby lymph nodes.

Stage IB

The tumor is larger or has grown deeper, but cancer cells are not found in nearby lymph nodes. The lung tumor is one of the following: the tumor is more than 3 centimeters across; ut has grown into the main bronchus; or it has grown through the lung into the pleura.

Stage IIA

The lung tumor is no more than 3 centimeters across. Cancer cells are found in nearby lymph nodes.

Stage IIB

The tumor is one of the following:

  • Cancer cells are not found in nearby lymph nodes, but the tumor has invaded the chest wall, diaphragm, pleura, main bronchus, or tissue that surrounds the heart.
  • Cancer cells are found in nearby lymph nodes, and one of the following:
    • The tumor is more than 3 centimeters across.
    • It has grown into the main bronchus.
    • It has grown through the lung into the pleura.

Treatments for Lung Cancer

The choice of treatment depends mainly on the type of lung cancer and its stage. People with lung cancer may have surgery, chemotherapy, radiation therapy, targeted therapy, or a combination of treatments.

People with limited stage small cell lung cancer usually have radiation therapy and chemotherapy. For a very small lung tumor, a person may have surgery and chemotherapy. Most people with extensive stage small cell lung cancer are treated with chemotherapy only.

People with non-small cell lung cancer may have surgery, chemotherapy, radiation therapy, or a combination of treatments. The treatment choices are different for each stage. Some people with advanced cancer receive targeted therapy. Cancer treatment is either local therapy or systemic therapy.

Local therapy

Surgery and radiation therapy are local therapies. They remove or destroy cancer in the chest. When lung cancer has spread to other parts of the body, local therapy may be used to control the disease in those specific areas. For example, lung cancer that spreads to the brain may be controlled with radiation therapy to the head.

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Systemic therapy

Chemotherapy and targeted therapy are systemic therapies. The drugs enter the bloodstream and destroy or control cancer throughout the body.

Your doctor can describe your treatment choices and the expected results.

Surgery

Surgery for lung cancer removes the tissue that contains the tumor. The surgeon also removes nearby lymph nodes.
The surgeon removes part or all of the lung:

  • A small part of the lung (wedge resection or segmentectomy): The surgeon removes the tumor and a small part of the lung.
  • A lobe of the lung (lobectomy or sleeve lobectomy): The surgeon removes a lobe of the lung. This is the most common surgery for lung cancer.
  • All of the lung (pneumonectomy): The surgeon removes the entire lung.

After lung surgery, air and fluid collect in the chest. A chest tube allows the fluid to drain. Also, a nurse or respiratory therapist will teach you coughing and breathing exercises.

Radiation Therapy

Radiation therapy (also called radiotherapy) uses high-energy rays to kill cancer cells. It affects cells only in the treated area. You may receive external radiation. This is the most common type of radiation therapy for lung cancer. The radiation comes from a large machine outside your body. Most people go to a hospital or clinic for treatment. Treatments are usually 5 days a week for several weeks.

Another type of radiation therapy is internal radiation (brachytherapy). Internal radiation is seldom used for people with lung cancer. The radiation comes from a seed, wire, or another device put inside your body. Learn more about Radiation for cancer treatment.

Chemotherapy

Chemotherapy uses anticancer drugs to kill cancer cells. The drugs enter the bloodstream and can affect cancer cells all over the body. Usually, more than one drug is given. Anticancer drugs for lung cancer are usually given through a vein (intravenous). Some anticancer drugs can be taken by mouth.

Chemotherapy is given in cycles. You have a rest period after each treatment period. The length of the rest period and the number of cycles depend on the anticancer drugs used. Learn more about chemotherapy.

Targeted Therapy

Targeted therapy uses drugs to block the growth and spread of cancer cells. The drugs enter the bloodstream and can affect cancer cells all over the body. Some people with non-small cell lung cancer that has spread receive targeted therapy.

There are two kinds of targeted therapy for lung cancer:

  • One kind is given through a vein (intravenous) at the doctor's office, hospital, or clinic. It's given at the same time as chemotherapy. The side effects may include bleeding, coughing up blood, a rash, high blood pressure, abdominal pain, vomiting, or diarrhea.
  • Another kind of targeted therapy is taken by mouth. It isn't given with chemotherapy. The side effects may include rash, diarrhea, and shortness of breath.