Causes and Diagnoses

Causes and Diagnoses of Lung Cancer

Approximately 440,000 deaths occur annually from tobacco use in the United States, according to the American Cancer Society. About 160,000 of those deaths are tied to lung cancer. Lung cancer accounts for 28 percent of all cancer deaths in the United States, with more than 80 percent of the cases of lung cancer being tied directly to smoking.

Risk factors

Individuals that are considered high-risk for lung cancer include:

  • Individuals 55–77 years old with no history of lung cancer
  • Former smokers who quit within the last 15 years

  • Current smokers with at least a “30 pack-year” history of smoking (30 pack years = one pack per day x 30 years or two packs per day x 15 years)

Additional risk factors for lung cancer:
  • Secondhand smoke

  • Radon exposure

  • Asbestos exposure

  • Talc (significant exposure)

  • Cancer-causing agents, such as:

    • Radioactive ores, like uranium
    • Nickel chromates
    • Arsenic
    • Coal products
    • Chloromethyl ethers
    • Mustard gas
    • Diesel exhaust
    • Vinyl chloride
  • Family or personal history of lung cancer
  • Air pollution

Smoking cessation

Smoking cessation can help reduce the risk of developing lung cancer. Studies have shown that the health benefits begin almost immediately after quitting smoking. Even heavy smokers who halve the amount they smoke see improvements in their overall health. Cigarette smoking is one of the most difficult addictions to overcome. The Northwestern Medicine Smoking Cessation Program is based on the most current and proven methods and includes a step-by-step plan for quitting, information on cessation medications and techniques for staying smoke-free.


The majority of lung cancers are diagnosed at an advanced stage when curative treatment may not be possible. However, the earlier a cancer is diagnosed, the easier it may be to treat. Northwestern Medicine offers low-dose screening CT scans to identify lung cancer in high-risk patients.

Screening tests are used to identify cancer before any symptoms are present. Until recently, there was no screening test for lung cancer. The Centers for Medicare & Medicaid Services now recommends annual screening for lung cancer with low-dose CT scans in high-risk individuals ages 55 to 77 years old.

The National Lung Cancer Screening Trial shows a 20 percent reduction in lung cancer deaths when a low dose CT scan was used instead of a chest X-ray to screen for lung cancer in high-risk individuals. This research study shows that annual screening for lung cancer is beneficial for individuals that are at high-risk of developing lung cancer.


Northwestern Medicine offers low-dose lung CT scans. Before having a scan, you will need to talk with your physician to determine your eligibility. Your physician will provide you with information, including potential risks and benefits of low-dose CT lung screening.

Risks of screening

Annual screening can help identify lung cancer in it's early stages, but screening does involve some risks, including:

  • False-positive: A test finding may falsely indicate that a scan shows something potentially cancerous. After further evaluation, it may be determined you do not have cancer. False positive findings can be very upsetting, since you believe that you have a diagnosis of cancer when, in fact, you do not.
  • False-negative: A scan may indicate that you do not have a suspicious finding on your scan. It is only later that your cancer is diagnosed, leading not only to a delayed diagnosis, but also delayed treatment.
  • Radiation exposure: The lung scan delivers a lower dose of radiation compared to a regular CT scan. The dosage of radiation exposure is similar to a cross-country airline flight.

Benefits of screening

  • Early detection: Lung cancer can be detected at a more treatable and possibly curable stage.
Your low-dose CT scan will be reviewed by a Northwestern Medicine radiologist. Your results will be sent to you via mail. Your referring physician will be provided a full explanation of results and recommendations for follow-up. Many lung nodules or abnormalities found on CT scans are NOT lung cancer. However, additional follow-up tests or repeat low-dose CT scans at a periodic interval may be recommended.


The most important step in preventing lung cancer is to stop smoking. Smoking is responsible for 85 percent of lung cancers. If you still smoke, your physician can provide guidance and assistance for smoking cessation resources.