Understanding Lung Cancer

Lung cancer is the nation's second most common major cancer, after breast cancer in women and prostate cancer in men. Though it remains challenging to treat, doctors and researchers are making steady advances in finding it earlier. Some important things to know:

  • Lung cancer has two main types: non-small cell and small cell.
  • Most lung cancers are non-small cell, which has more treatment options.
  • Smoking remains the leading cause of lung cancer.

Lung Anatomy

A diagram of a women's lungs and the surrounding organs.

What is lung cancer?

Lung cancer occurs when abnormal cells develop in one or both lungs and then grow so quickly that the body's immune system cannot keep up. The abnormal cells can form tumors that keep your lungs from working. Left untreated, the cancer can spread to nearby lymph nodes and other parts of your body.

Who gets lung cancer?

More than 13 percent of new cancers in the United States are lung cancers. In 2018, an estimated 234,000 people in the U.S. will be diagnosed with lung cancer. In 2015, an estimated 541,000 in the U.S. were living with lung cancer.

Risk factors

Smoking: Smoking accounts for as much as 90 percent of lung cancers. It brings substances into the body that damage cells lining the lungs. Stopping smoking can significantly reduce the risk of many cancers and other diseases. Still, nearly 60 percent of lung cancers are diagnosed in people who have quit.

Secondhand smoke: Exposure to secondhand smoke causes thousands of lung cancer cases in the U.S. each year.

Gender: Overall, lung cancer in the U.S. is more common in men than women, with about 64 cases per 100,000 among men and 48 per 100,000 among women. For white and Latino people ages 30 to 54, however, rates are higher among women. The reasons are not fully understood. Rates have fallen for both genders in this group since 1995, but they've fallen faster for men.

Race: African-American men are 20 percent more likely than white men to develop lung cancer. Latinos and Asians/Pacific Islanders are significantly less likely than other groups to get lung cancer.

Age: In the U.S., more than two-thirds of patients are 65 or older when diagnosed.

Environment: Exposure to pollutants such as fuel exhaust and chemical vapors can increase risk. Exposure to radon gas, which can build up in homes and other buildings from the natural breakdown of uranium in soil, also increases risk.

Family history: Inherited genes can increase risk among smokers and nonsmokers. If you have a family history of lung cancer or worry that you’re at high risk, we offer expert genetic counseling and risk assessment to help you learn about and manage your risk.

Lung cancer outcomes

Lung cancer remains difficult to treat, especially because many patients are diagnosed in later stages. This means that overall survival rates remain discouraging. It’s important to know, though, that survival rates are only averages and can’t predict the outcome for any one patient.

Signs of hope: Survival rates have risen substantially over the past decade. Among patients whose cancer is caught before it has spread from where it started, more than half survive five years or longer.

Quality of life: At the OHSU Knight Cancer Institute, we are devoted to giving every patient the longest life and highest quality of life possible, regardless of diagnosis or outlook.

Lung cancer types

Lung cancer has two main types, each with several subtypes.

Non-small cell lung cancer: This covers several types in which cancer cells form in lung tissue. Each is named for the type of cell it develops in. This group of lung cancers makes up about 85 to 90 percent of cases.
  • Squamous cell carcinoma: This type begins in squamous cells. These thin, flat cells form the surface of the skin, the lining of hollow organs and the lining of respiratory and digestive tracts. Also called epidermoid carcinoma, this cancer most often develops in smokers.
  • Large cell carcinoma: This cancer may begin anywhere in lung tissue. It tends to grow more rapidly than other non-small cell cancers.
  • Adenocarcinoma: This slow-growing cancer type usually appears in the areas around the lungs. It occurs most often in smokers but is the most common type of lung cancer in nonsmokers.
  • Other: Less common types include pleomorphic, carcinoid tumor, salivary gland carcinoma and unclassified carcinoma.

Small cell lung cancer: This aggressive cancer forms in lung tissue and can spread to other parts of the body. It occurs almost exclusively in heavy smokers and represents about 10 to 15 percent of lung cancers. Subtypes include small cell carcinoma, also called oat cell cancer, and combined small cell carcinoma.

Symptoms of lung cancer

Lung cancer typically doesn't cause symptoms in early stages, and some symptoms can be caused by other conditions. Lung cancer is sometimes discovered after a chest X-ray for another condition. Talk with your doctor if you're concerned about:

  • Chest discomfort or pain
  • Bone pain
  • A cough that doesn't go away or worsens
  • Shortness of breath
  • Wheezing
  • Blood coughed up from the lungs
  • Hoarseness
  • Loss of appetite
  • Weight loss for no known reason
  • Severe fatigue
  • Headaches
  • Trouble swallowing
  • Swelling in the face and/or neck veins

Lung cancer screening

Cancer is easiest to treat when it's found early. Lung cancer can be difficult to detect in early stages, and there is no routine screening.

In response to a National Lung Screening Trial completed in 2010, the government approved annual screening for some high-risk patients covered by Medicare Part B. Those eligible for an LDCT (low dose computed tomography) scan must: 

  • Get a doctor's approval
  • Be 55 to 77 years old
  • Have no sign of lung cancer
  • Be a smoker, or have quit in the last 15 years
  • Have a smoking history of at least one pack a day for 30 years 

Researchers and providers are working to win government approval to expand screening to more people at risk.

Diagram illustrating tumor sizes.

Lung cancer staging

Staging helps doctors see whether and how far lung cancer has spread. This helps guide treatment options. Your care team will determine the stage of your cancer based on:

  • The size of the main tumor and whether it has grown into nearby areas
  • Whether the cancer has spread to lymph nodes
  • Whether the cancer has spread to other organs or body parts

Non-small cell lung cancer:

Stage I

The tumor is less than 3 centimeters at its largest dimension (with one rare exception) and has not spread to the membranes surrounding the lungs.

Stage II

Stage IIA: The tumor is bigger than 4 centimeters but no bigger than 5 centimeters, and cancer has not spread to lymph nodes. Cancer has spread to the bronchus (airway connecting the lung to the windpipe) and/or to a membrane around the lung (pleura) and/or is linked to atelectasis (lung collapse) or obstructive pneumonitis (inflammation).

Stage IIB: One of these applies:

  • The tumor is no larger than 5 centimeters, and cancer has spread to nearby lymph nodes on the same side as the tumor. Cancer affects the bronchus and/or a membrane around the lung and/or is linked to atelectasis or obstructive pneumonitis.
  • Cancer has not spread to lymph nodes. The tumor is bigger than 5 centimeters but no bigger than 7 centimeters, or cancer has spread to any of these: a chest membrane, chest wall, a nerve between the lung and heart (phrenic nerve), or tissue around the heart; or a tumor(s) has developed in the same lobe as the main tumor.

Stage III

Stage IIIA: One of these applies:

  • The tumor is no bigger than 5 centimeters, and cancer has spread to nearby lymph nodes on the same side as the tumor or to nodes under where the windpipe branches (carina) into each bronchus (airway connecting the lung to the windpipe). Cancer also may affect the bronchus and/or a membrane around the lung and/or is linked to atelectasis (lung collapse) or obstructive pneumonitis (inflammation).
  • The tumor is bigger than 5 centimeters but no bigger than 7 centimeters, or cancer has spread to any of these: A chest membrane, chest wall, a nerve between the lung and heart (phrenic nerve) or to tissue around the heart; or a tumor(s) has developed in the same lobe as the main tumor.
  • Cancer has not spread to the lymph nodes, or it has to spread to nearby lymph nodes on the same side as the tumor. The tumor is bigger than 7 centimeters and has spread to at least one other nearby organ such as the heart or windpipe.

Stage IIIB: One of these applies:

  • Cancer has spread to lymph nodes on both sides or above the collarbone. The tumor is no bigger than 5 centimeters, and cancer also may affect the bronchus and/or a membrane around the lung and/or is linked to atelectasis or obstructive pneumonitis.
  • The tumor is bigger than 5 centimeters and has spread as far as to nearby organs such as the heart or windpipe. Cancer has spread to lymph nodes only on the same side or to nodes under where the windpipe branches into each bronchus.

Stage IV

The tumor is any size, and lymph nodes may or may not be affected, plus:

Stage IVA: Tumor(s) have developed in the other lung, and complications have arisen such as fluid buildup around the heart or lung.

Stage IVB: A tumor has developed in one organ outside the chest.

Stage IVC: Tumors have developed in one organ outside the chest or cancer has spread to more than one organ outside the chest.