• Michael Misialek, MD

What is Liquid Biopsy?

Liquid biopsies are non-invasive blood tests that detect circulating tumor cells (CTCs) and fragments of tumor DNA that are shed into the blood from the primary tumor or metastatic sites. Liquid biopsies are integral to the success of precision medicine, allowing for the analysis of genetic mutations that make each tumor unique.

It is a sensitive technique that quickly tracks a patient’s response to cancer treatments. So called “actionable targets” can be easily quantified from a limited sample volume.

In contrast to a conventional tissue biopsy which can be costly, difficult to obtain, painful and take time to process and analyze, liquid biopsy is simple, fast and no more uncomfortable than a typical blood draw. A tissue biopsy provides a single snapshot in time, typically at the beginning of treatment. Liquid biopsy can be performed at any time throughout treatment to track response.

During treatment, because of tumor heterogeneity, genetic mutations can evolve over time. It is not feasible to continuously take tissue biopsies. Additionally, metastases can differ in their genetic composition than the primary.

Liquid biopsy allows for real time tracking, is relatively inexpensive, less invasive, less risky, easier and less costly than tissue biopsy. It allows for physicians to stay on top of tumor characteristics. It can be performed more frequently and provides precise up to date information on treatment, allowing for quicker decisions on therapy.

As such, treatment can be more quickly tailored to match the continuously evolving genetic makeup of a tumor. For instance, resistance to treatment can be detected sooner and acted upon, sparing patients ineffective treatments that might even be harmful.

Liquid biopsy also allows for a greater understanding on the basic science level of tumor biology and metastatic potential and promises to advance research at a faster potential than relying on tissue samples alone. CTCs are the most widely studied, however, cell free DNA (cfDNA) is also gaining in popularity.

The Association for Molecular Pathology, after reviewing more than 200 studies, issued a statement citing "Our literature survey concluded that measuring circulating tumor cell burden in metastatic breast and prostate cancer has already crossed a prognostic threshold for clinical utility.” However, larger studies are needed.

Liquid biopsies have already been proven effective in breast cancer, recently making news at the recent San Antonio Breast Cancer Symposium.

Progress has also been seen in many other cancers, including liver, pancreas, brain and colon. Recently platelets (cells in the blood critical to clotting) are showing promise as a better source of tumor genetic information for liquid biopsy.

Pathologists are crucial to the success of precision medicine and have been leaders in advancing liquid biopsies. Pathologists are needed to ensure testing is accurate and precise through standardization and strict quality control. Pre-analytic factors such as blood collection, processing, storage, and DNA extraction, quantification, analysis and reporting of data need close oversight by pathologists.

Liquid biopsies are yet another exciting advance in precision medicine. Follow Path Report for updates as more information is learned.

#precisionmedicine #liquidbiopsy #pathology #treatment

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