What to Know About Low or Elevated Labs for Lung Cancer

Many tests are used to diagnose lung cancer, including imaging scans and laboratory tests. Biomarker testing is a lab test used to look for abnormal genes, proteins, and other substances in the blood or other body tissues associated with cancer.

Biomarker testing can:

• Detect lung cancer in an early stage
• Estimate how fast the cancer will grow and spread 
• Choose the best treatment to improve patient outcomes 
• Monitor cancer during and after treatment

This article explores the importance of lab testing for diagnosing lung cancer, the different lab tests used, how to understand biomarker testing results, and what to expect after testing is complete.

The Importance of Lab Testing for Diagnosing Lung Cancer

Laboratory (lab) tests evaluate a sample of bodily fluids or tissue under a microscope and are essential to help detect and diagnose lung cancer before the disease has metastasized (spread). Labs also provide information about a person’s overall health and help healthcare providers choose the best cancer treatments.

Types of Labs for Lung Cancer 

There are several different types of lab tests used for lung cancer. Your healthcare provider will consider your symptoms, age, overall health, and other medical test results to decide which diagnostic tests to use. 

Blood Tests

The two types of blood tests commonly used for lung cancer are:

Complete blood count (CBC): A CBC measures the different types and volumes of blood cells: red blood cells, white blood cells, and platelets. CBC is often taken at diagnosis and to monitor a person’s health during and after treatment.

Blood chemistry: This panel measures the amounts of substances such as electrolytes, enzymes, fats, metabolites, and proteins released into the blood by organs and tissues. If lung cancer has spread to other areas of the body, it can change the functioning of the organ it has spread to and create an imbalance in the levels of these substances. 

Sputum Cytology

If you have a persistent cough, your healthcare provider may take a sputum (mucus coughed up from the lungs) sample to examine it in the lab to check for cancer cells. Sputum cytology tests often involve taking early-morning mucus samples for three days to detect lung cancers that develop in the lungs’ major airways.

Comprehensive Metabolic Panel

A comprehensive metabolic panel (CMP) consists of 14 different blood tests (taken from a single blood draw) to assess your overall health and give your healthcare provider information on your blood sugar, electrolyte levels, fluid balance, kidney and liver functioning, and protein levels. Imbalances in certain values may indicate the presence of cancer cells.

Thoracentesis

Lung cancer may cause fluid to surround the lungs (pleural effusion). Healthcare providers perform thoracentesis, which involves placing a needle between the ribs to remove the fluid. The fluid is examined in the lab to check for cancer cells. Thoracentesis procedures may be repeated if the fluid returns and causes difficulty breathing.

Biopsy Samples 

A biopsy involves removing a small tissue sample from a mass or area where cancer is suspected to examine it in the lab and check for cancer cells. Tissue samples can be collected through a needle biopsy, thoracoscopy, or bronchoscopy.

Biomarker Testing

Lung cancer biomarkers, or tumor markers, are biological molecules produced by cancer cells or other cells in response to cancer. Biomarker testing can be used to assess your risk of developing cancer, diagnose lung cancer, determine effective treatments, and, after the initial diagnosis, look for specific changes (mutations) in the DNA and protein levels in the tumor. 

Understanding High or Low Biomarkers 

Normal ranges for each biomarker test result should be written on your biomarker testing report. Your healthcare provider will review your results with you, explain each biomarker, and discuss how your results will be used to choose your treatment(s) and care plan. 

Important lung cancer biomarkers include:

• Circulating tumor cells (CTCs): When cancer cells are present and growing, they “shed” and release cells known as circulating tumor cells into the bloodstream. An elevated CTC level can help your healthcare provider detect mutations to help guide treatment.
• Driver mutations: Changes in the DNA sequence of genes can cause cells to become cancerous. Your report will list the several known lung cancer mutations and indicate whether your tumor has that specific mutation. Targeted therapies for each particular mutation may also be included in the report.
• PD-L1 protein expression: A high level of this protein may mean your tumor is more likely to respond well to immunotherapy treatments. 

While You Wait for Your Results

Once your blood or tissue sample is taken, your care team will review and interpret your test results. On average, biomarker blood test results take five to seven days, and biomarker testing on a tissue sample collected via biopsy takes two to four weeks.

Waiting for test results can be nerve-racking, but there are things you can do to cope while you wait:

• Talk or write about your worries.
• Spend time with supportive people.
• Practice mindfulness and self-care.

What Happens After Lab Testing

Your healthcare providers will use your biomarker test results to help detect lung cancer, guide your treatment plan, and select targeted therapies or immunotherapies to treat your specific cancer. 

Depending on the mutation(s) present, your healthcare provider may prescribe targeted therapies approved by the Food and Drug Administration (FDA) or match you with a clinical trial testing a targeted therapy for a specific mutation. If you have a high level of the PD-L1 biomarker, your healthcare provider may recommend FDA-approved immunotherapy.

Should You Get a Second Opinion?

Lung cancer is a life-altering diagnosis, and it’s important you trust your cancer care team. Many patients seek a second opinion, and it is well within your rights to ask for one. Reasons you may want to get a second opinion include:

• You’re unhappy with your current cancer care team. 
• You want to know if other treatment options are available.
• Your healthcare provider is unfamiliar with or unwilling to provide biomarker testing.
• Your cancer isn’t responding to current treatments. 

Summary

Lab tests, such as biomarker testing, can help diagnose lung cancer, look for specific gene mutations and proteins to shed light on a patient's type of lung cancer, and aid healthcare providers in finding the most suitable treatment. Biomarker testing can be used throughout a patient's lung cancer journey and may be used to:

• Screen for and detect lung cancer
• Estimate how quickly cancer will metastasize 
• Identify the best-targeted therapies or immunotherapies
• Monitor the cancer during treatment to evaluate if it's working

Researchers continue to make breakthroughs in identifying lung cancer biomarkers and targeted therapies. Talk with your healthcare provider about biomarker testing and how it may benefit your treatment plan.

A Word From Verywell

Undergoing lab tests and waiting for the results can be an overwhelming experience. A lung cancer diagnosis is life-changing, but there is reason to have hope. Advancements in lung cancer screening, testing, and targeted therapies have helped make significant improvements to lung cancer care and survival rates in recent years. Talk with your healthcare provider about lab tests that may help them identify targeted therapies to treat your specific type of lung cancer.