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This article waslast modified on July 10, 2017.

In June, the U.S. Food and Drug Administration (FDA) approved the first blood-based genetic test to guide the treatment of a common type of lung cancer called non-small cell lung cancer (NSCLC). Traditionally, samples of cancerous tissue that need to be tested are obtained through biopsy procedures. The recently approved testing technique is based on the principle that all growing cells, including cancerous cells, shed DNA into the blood. The DNA in the blood can be tested instead of tumor tissue. This technique is often referred to as a "liquid biopsy" because it does not require an invasive procedure to obtain a solid tissue sample for analysis.

The newly-approved test analyzes DNA that has been shed from tumors in the blood of NSCLC patients and looks for abnormalities that could indicate that the tumor is more likely to respond to a drug called erlotinib. This type of test is called a "companion diagnostic" test because it is meant to be used as a way to guide a specific drug treatment.

Mutations in a gene called epidermal growth factor receptor (EGFR) are present in 10% to 20% of NSCLCs. EGFR is a protein found on the surface of cells that regulates their growth, division, survival, and death. Certain defects called "activating mutations" in the EGFR gene can result in excessive signaling for growth and uncontrolled proliferation of cancer cells. Erlotinib belongs to a class of drugs called tyrosine kinase inhibitors (TKIs), which enter cancer cells and impede EGFR signaling, thus inhibiting the cancer cells' growth.

Patients who have non-small cell lung cancers that test positive for the EGFR activating mutations may respond to erlotinib, while those who test negative are unlikely to respond. Using such tests to help determine what drugs may or may not be effective for an individual is a form of personalized medicine and is a valuable molecular approach in cancer therapy.

"Liquid biopsy tests make it possible to deliver highly individualized health care for patients," said Alberto Gutierrez, Ph.D., director of the Office of In Vitro Diagnostics and Radiological Health in the FDA's Center for Devices and Radiological Health in a press release. "Liquid biopsies have the potential to allow physicians to identify patients whose tumors have specific mutations in the least invasive way possible."

According to the American Cancer Society, lung cancer is the third most common cancer in adults and the leading cause of cancer death among both men and women; about 1 in 4 cancer deaths are due to lung cancer. The vast majority of cases of lung cancer, about 80% to 85%, are non-small cell lung cancer.

Erlotinib can be used as a stand-alone treatment for patients with advanced-stage NSCLC who carry activating mutations in the EGFR gene. These mutations are more common in women and non-smokers. It is not uncommon for NSCLC tumors to acquire additional mutations that make them resistant to drugs like erlotinib. This is another advantage of using liquid biopsy as the patients can be more easily monitored in the future for these additional mutations.


(June 1, 2016) U.S. Food and Drug Administration. FDA Approves First Blood Test to Detect Gene Mutation Associated With Non-Small Cell Lung Cancer. Available online at Accessed June 10, 2016.

(June 1, 2016) Genomeweb. Roche Liquid Biopsy Test First to Garner FDA Approval. Available online at Accessed June 10, 2016.

(May 16, 2016) American Cancer Society. What Is Non-Small Cell Lung Cancer? Available online at Accessed June 10, 2016.

(May 16, 2016) American Cancer Society. Key Statistics For Lung Cancer. Available online at Accessed June 11, 2016.