Lung cancer is the second-most common type of cancer, and the earlier it’s diagnosed, the better the outlook tends to be. But most people with lung cancer don’t know they have it until the disease has spread outside their lungs.

Screening tests such as medical imaging scans can help detect lung cancer, but they come with inherent risks and are recommended only for people at high risk of lung cancer.

Researchers are working on developing blood tests that could detect lung cancer before it becomes symptomatic.

In this article, we look at how a blood test for lung cancer might work and how it’s different from the diagnostic tools available today.

Imaging tests are usually done when your doctor suspects you might have lung cancer. There are many imaging tests, but they all offer different ways to see inside of your body.

Imaging tests for lung cancer

Imaging tests that a doctor might order to check for lung cancer include any of the following:

  • A chest X-ray can look for masses in or around your lungs.
  • A CT scan is more detailed than an x-ray and creates cross-sectional images of your body.
  • An MRI scan can also be used to look for cancer, but in the case of lung cancer, it’s usually used to see whether it’s spreading.
  • A PET scan uses dye to look for cancer cells and can help determine where cancer is spreading.
  • A bone scan is specifically good at finding cancer that has spread to your bones.

Diagnostic tests for lung cancer

If the imaging tests indicate that you might have lung cancer, it will be confirmed with a diagnostic test. These tests involve taking a tissue sample from your body and examining it in a laboratory. Diagnostic tests for lung cancer include the following:

  • A sputum cytology examines material such as mucus that has been coughed up from your lungs.
  • A thoracentesis is a test that involves a doctor taking a sample of fluid from around your lungs using a special needle that goes between your ribs.
  • A needle biopsy is similar to a thoracentesis, but a small piece of tissue is taken instead of fluid.
  • A bronchoscopy is a procedure where a doctor inserts a special tube down your airway to look at your lungs or take a tissue sample from your bronchi.

The allure of blood tests for lung cancer diagnosis and screening

While not yet available, a blood test for lung cancer would help speed up diagnosis while using less invasive measures. In addition, lung cancer blood tests may be able to determine not only if you have lung cancer but also:

  • what type of lung cancer you have
  • how well the disease will respond to treatment
  • your long-term outlook
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Researchers are looking for ways to use biomarkers in your blood to detect lung cancer before you start experiencing any symptoms.

Doctors use biomarkers to objectively measure your health. In the case of lung cancer, antibodies, protein, and abnormal DNA are shed from cancer cells, which may likely be used for lung cancer screening.

Benefits of blood tests for lung cancer

There are many benefits to using blood samples to test for lung cancer.

Routine blood testing is already a well-established procedure. There are many offices and laboratories capable of administering blood tests. Most doctor offices can take a blood sample for testing. Some drugstores can take blood samples, too.

It’s also a procedure requiring very little inconvenience for most people. No anesthetics, special dyes, or large machines are needed to take a blood sample, and it can be done in just a few minutes with minimal side effects.

Current research into developing a lung cancer blood test is encouraging, but more work is still needed to validate the results. We will probably not see routine lung cancer blood tests for at least a few years.

Early screening means looking for lung cancer when you don’t have any symptoms or history of lung cancer.

The U.S. Preventive Services Task Force (USPSTF) is a nongovernmental advisory group made up of experts in disease prevention. Their recommendation is that early screening for lung cancer should be limited to people at high risk of lung cancer. Specifically, this means current and former smokers between the ages of 50 and 80.

At first, you might think everyone should be regularly screened. The issue is that there aren’t any lung cancer tests that are completely free of risks.

A low dose computed tomography (LDCT) imaging scan is the most common screening tool for people who aren’t exhibiting any signs of lung cancer. These scans are recommended annually for people with a high risk of lung cancer. If you have one of these scans, you’ll be exposed to a limited amount of radiation.

While the radiation exposure of an LDCT scan has only a small risk, it’s not zero. This is why annual LDCT scans are recommended only for a select population.

Does lung cancer show up in routine blood work?

Experts are currently researching whether your blood reliably contains biomarkers of lung cancer. As of right now, lung cancer is not something that a routine blood test can accurately diagnose.

At what stage is lung cancer most commonly diagnosed?

Lung cancer is usually diagnosed after it’s distantly spread throughout the body. But the rate of late stage diagnoses for lung cancer has been dropping over the past 20 years, partly due to the adoption of LDCT screenings.

What are survival rates for early/late diagnosis?

According to the American Cancer Society, the 5-year relative survival rate is very different depending on how early the cancer is detected.

  • If non-small cell lung cancer is diagnosed before spreading outside the lungs, the 5-year relative survival rate is 64 percent.
  • When non-small cell lung cancer has spread to nearby structures or lymph nodes at the diagnosis, the 5-year relative survival rate is 37 percent.
  • If non-small cell lung cancer has spread to other parts of the body before it’s diagnosed, the 5-year relative survival rate is 8 percent.

What are the early symptoms of lung cancer?

Early on, the symptoms of lung cancer are similar to those of many other conditions, not all of which are cancerous. But if you suspect you might have lung cancer, see a doctor as soon as possible to find out.

Early symptoms often include:

Blood tests are not yet available to screen for lung cancer, but this is something researchers are working toward. Many types of biomarkers in blood might be used to indicate asymptomatic lung cancer.

Until a routine blood test is available, you can improve your lung cancer outlook by getting an annual LDCT scan if you meet the qualifications. Also, if you smoke, you may want to consider quitting.

Quitting smoking can reduce your risk of lung cancer or even improve your outlook if you already have cancer.