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Serial Liquid Biopsies Allow for Tracking of Resistance Mutations in GI Cancers

Pashtoon M. Kasi, MBBS, MD, MS
Published Online:7:47 PM, Tue August 6, 2019

Pashtoon M. Kasi, MBBS, MD, MS, clinical assistant professor of internal medicine, University of Iowa Carver College of Medicine, discusses how serial testing via liquid biopsies in patients with gastrointestinal cancers can provide oncologists with a better picture of the patient’s condition and potential acquired mechanisms of resistance. He explains that multiple liquid biopsies are especially helpful for the management of colorectal cancer when patients progress on anti-EGFR therapies to identify and track potential acquired RAS mutations.
Kasi lead a study of 322 patients in which serial biopsies were conducted to monitor potential changes in each patient’s disease using the Guardant360 assay. In the study, researchers were able to identify RAS/RAF wild type (n = 214), RAS mutations (n = 83), BRAF V600E mutations (n = 18), non–BRAF V600E mutations (n = 7), HER2 amplifications (n = 13), HER2 mutations (n = 7), and microsatellite instability–high (n = 3). Recognizing these alterations helped with treatment modification and clinical trial selection for these patients.
Since these clones decay overtime, says Kasi; using serial testing to see the presence or absence of select mutations or amplifications lets physicians know when to re-challenge the patient with a chosen therapy. According to Kasi, many studies have already shown the value in this method.
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