What is a Liquid Biopsy?

The new technology has the ability to revolutionize breast cancer care.

A liquid biopsy is commonly used in clinical and laboratory research to identify and measure biomarkers. Several sessions at the 2019 AACR Annual Meeting in Atlanta were dedicated to this topic. These blood-based tests give researchers the ability to look at the unique characteristics of a cancer cell, without performing an invasive procedure.

What is a biomarker?

To understand the promise of liquid biopsy, we must first understand biomarkers and how they are used.

A biomarker can be thought of as a molecular flag that helps doctors decide on a course of action for each patient. A biomarker can be a gene, protein, or other measurable marker and should consistently mean the same thing.

For instance, a mutation in the BRCA1 gene is a biomarker for a high risk of breast, ovarian and other cancers. When detected before cancer, surgical removal of the breast and/or ovaries can prevent a future breast or ovarian cancer. When detected after a cancer diagnosis, a germline (inherited from a parent) or somatic (occurring only in the tumor cells) provides clues to what kinds of treatment is most likely to kill the tumor cells.

Advances in liquid biology technology and the remarkable pace of discovery of potential new biomarkers makes liquid biopsies a valuable research tool. Liquid biopsies allow clinical researchers to get non-invasive serial samples of blood, urine or other bodily fluid as the patient progresses through treatment. The goal is to move liquid biopsy from the research arena into the clinical arena where it can improve the care of patients and we’re making progress in that direction.

Circulating tumor cells (CTCs) are another example of a biomarker that can be measured in the blood of cancer patients. The presence of CTCs has been shown to predict recurrence after treatment of early-stage breast cancer. Changes in the number of CTCs during treatment can indicate that a tumor is not responding to treatment or has spread to other tissues.

Coupled to single-cell analysis where changes in tumor markers can be measured in individual tumor cells, liquid biopsies are helping researchers to understand the process of tumor evolution – progression from a primary cancer to metastasis – and help identify new targets for prevention or treatment of metastasis.

The promise of liquid biopsy

As the underlying technology of liquid biopsy continues to evolve, researchers are discovering circulating factors beyond genes and proteins that can provide clues to tumor response, progression and cancer risk.

Liquid biopsies hold tremendous promise for patient care: they can reduce the need for tissue biopsies – an invasive and sometimes painful procedure – as well as the number of imaging appointments to determine the tumor’s response to therapy, or to augment screening mammography.

The hope is that liquid biopsies will routinely be used for these purposes, but also to detect early-stage breast cancer or identify biomarkers of risk before cancer occurs. This continues to be a major focus in the liquid biopsy field.

One of the prevailing challenges is that rapid pace of biomarker discovery with liquid biopsy is outpacing our capacity to verify that the biomarkers that are found are clinically meaningful.  This takes carefully designed clinical trials and patient volunteers.

As with many discoveries that have improved breast cancer, BCRF has supported the development and application of liquid biopsy by funding innovators who have moved the field forward, such as Daniel Haber, James Hicks, Michael Wigler and many others who are now applying the technology to their research studies to accelerate biomarker discovery.