Dr. Kasi on the Use of Liquid Biopsies in CRC

Pashtoon M. Kasi, MBBS, MD, MS, hematologist, internist, oncologist, Mayo Clinic, discusses the comparison of the circulating tumor DNA tests, tissue, and liquid biopsies, in a study of patients with colorectal cancer (CRC).

In an analysis of 322 patients with CRC, patients were stratified in terms of liquid biopsies prior to treatment and after they started therapy. Concordance between liquid and tissue biopsies was similar almost every time prior to treatment initiation. However, concordance markedly fell when a patient was responding to treatment or if they did not have the same amount of cancer, according to Kasi.

It is important to know what liquid biopsy assays are being ordered, explains Kasi. Some assays may not cover the gene or an aberration. If the biopsy report comes back as negative, it does not necessarily mean the test is negative. Rather, it could mean there is not enough shedding in the blood or the assay does not have the detection capacity, according to Kasi. Many of these commercially available assays are panel-based and not focused on one tumor. As an oncologist, it is important to know whether the relevant, guideline recommended, potentially actionable aberrations are present or not.