Understanding the Power of Liquid Biopsies to Detect Cancer
Tissue biopsies have long been the standard for analyzing gene mutations in cancer to determine how likely it is to spread. But because there are patients who are unable to undergo invasive biopsies or whose tumors are not reachable, there are minimally or non-invasive procedures that complement or serve as alternatives to tissue biopsies.
Liquid biopsies are screening tools that are receiving much attention for their ability to detect and characterize tumors. Liquid biopsies are essentially blood tests, making them safer than tissue biopsies that come with the risk of complications like bleeding, infection or injury to surrounding tissue. The turnaround time for results is also quicker compared to tissue specimens. As a safe, non-invasive alternative to obtaining tumor material, liquid biopsies allow for cost-effective serial sampling.
How Do Liquid Biopsies Work?
The blood of patients with cancer may contain intact circulating tumor cells (CTCs) and circulating tumor DNA (ctDNA). When tumors grow in volume, ctDNA gets released into the bloodstream. Therefore, doctors can draw blood from a patient to analyze whether ctDNA has been released and present in the plasma.
Liquid biopsies typically only require two vials or less of blood. The blood sample’s genetic material is then analyzed through whole-genome sequencing (WGS). DNA abnormalities, RNA expression, protein expression, translocations, chromosomal abnormalities and point mutations can be evaluated through molecular analysis. WGS maps the genome, tracking mutations and markers associated with cancer.
What Are Liquid Biopsies Uses?
Liquid biopsies can help detect cancers earlier than radiology and imaging, allowing physicians to identify the type of cancer, tumor’s gene expression and presence of mutations that may be resisting administered treatment.
One of the ways that liquid biopsies may perform better than tissue biopsies is when the tumor has spread to other sites in the body or has metastasized. Multiple invasive tissue biopsies would have to be performed to analyze each potential tumor site. On the other hand, liquid biopsies provide an overview of the extent of the mutations, possibly including tumor locations that are too difficult to reach via needle or surgery.
The results of the test also help physicians with customizing treatment through genotyping. For example, when a patient’s body seems to be resisting specific administered therapies, a liquid biopsy may be performed again to identify the mechanisms of resistance. And after treatment, liquid biopsies can be used to measure the presence of residual cancer cells and assess the probability of relapse.
Because of the benefits of liquid biopsies, research and development continue to improve liquid tests or methods. Some methods have already received regulatory approval. In 2020 alone, the FDA approved two liquid biopsy methods; one can detect alterations in solid tumors while the other detects epidermal growth factor receptor (EGFR) mutations in lung cancer cells.
