In August 2020, the Federal Drug Administration (FDA) approved two liquid biopsy tests – the Guardant360 CDx test and FoundationOne Liquid CDx test. Read on to find out what the implications are for the colorectal cancer community.
What is a Liquid Biopsy?
A liquid biopsy is a non-invasive blood test that detects ctDNA, freely circulating DNA in the blood that is released when tumor cells die. Unlike a tumor biopsy, which often requires surgery, liquid biopsies only require a sample of blood, and are quicker, easier, and less painful to obtain.
Guardant360 CDx Liquid Biopsy
On August 7, Guardant Health announced that their test called Guardant360 CDx was the “first liquid biopsy companion diagnostic (CDx) that uses next-generation sequencing (NGS) technology to identify patients with specific types of mutations of the epidermal growth factor receptor (EGFR) gene in a deadly form of metastatic non-small cell lung cancer (NSCLC).”
CDx is an abbreviation for a companion diagnostic. According to the FDA, “A companion diagnostic is a medical device, often an in-vitro device (meaning used in the body vs. in a lab), which provides information that is essential for the safe and effective use of a corresponding drug or biological product. The test helps a healthcare professional determine whether a particular therapeutic product’s benefits to patients will outweigh any potential serious side effects or risks.”
So what does this have to do with colorectal cancer? This specific test looks at 55 tumor genes at once, compared to just one gene at a time. The approval is not only aimed at better understanding which lung cancer patients have EGFR mutations and would benefit from treatment with a specific drug, but it also provides insight on biomarker mutations for individuals with solid tumors like CRC, ultimately providing insight into treatment decisions.
FoundationOne Liquid CDx Liquid Biopsy
Then, on August 27, 2020, Foundation Medicine announced that their liquid biopsy test, FoundationOne Liquid CDx, also received FDA approval. FoundationOne Liquid CDx looks for mutations or alterations for 324 genes that have implications for cancer care.
Like Guardant360 CDx, this test is also a companion diagnostic. Specifically, it’s a CDx for FDA approved therapies in prostate cancer and NSCLC, however the test also provides vital information for patients with CRC, including mutations in biomarkers such as KRAS and BRAF to name a few. It can also determine Microsatellite Instability (MSI-H) status, and Tumor Mutational Burden (TMB).
TMB describes the number of mutations in a tumor. The higher the TMB score, the more likely the immune system is to recognize the tumor and issue an immune response.
The Future of Liquid Biopsies, Biomarkers, & Colorectal Cancer Treatment
According to Dr. Chris Lieu, “This is an exciting time in the development and approval of new tools to better understand and test the biology and biomarkers for colorectal cancer. Liquid biopsies to evaluate circulating tumor DNA (ctDNA) may help patients and their care teams use a new technology to find better treatments for colorectal cancer, both in earlier and later stages.”
We encourage all patients to have their biomarkers tested. If you have not had your biomarkers tested, are unsure, or want to pursue a liquid biopsy, it’s important to speak to your oncologist, as this information can have treatment implications. Although liquid biopsies are relatively new to the cancer space, the information they can provide is crucial to tailoring cancer care.