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REDWOOD CITY, Calif., Aug. 05, 2019 (GLOBE NEWSWIRE) -- In the largest comparison of blood-based microsatellite instability (MSI) testing to traditional tissue methods across multiple solid tumor types, researchers demonstrated that the Guardant360® assay can accurately detect MSI, an important biomarker used to predict response to immunotherapy regardless of tumor type. Researchers from Guardant Health, The University of Texas MD Anderson Cancer Center, the Samsung Medical Center, and other institutions reported the findings in Clinical Cancer Research.
For advanced cancer patients, MSI is a good predictor of response to immunotherapy with PD-1 and PD-L1 inhibitors in multiple tumor types. It has been reported to occur in about 1% of cases, and any patient with advanced cancer who is found to be MSI-High is eligible for treatment with immunotherapy. MSI-High occurs most frequently in colorectal, endometrial, and gastroesophageal cancers.
“Unfortunately, less than half of all advanced colon cancer patients are tested for this important biomarker. And across all solid tumors, we suspect the testing rate is far lower, in part due to challenges of working with tissue samples,” said Jeeyun Lee, MD, Associate Professor, Division of Hematology/Oncology, Samsung Medical Center. “By incorporating these results into a simple blood test, we should be able to increase the number of patients who get this information and benefit from appropriate immunotherapy.”
To validate Guardant360’s MSI detection, researchers compared the results of 1,145 Guardant360 samples to MSI status determined using standard-of-care tissue testing results taken from medical records. The results from Guardant360 were the same as the standard-of-care tissue test in 98.4% of cases.
Additionally, it is the first report of immune checkpoint inhibitor therapy outcomes in plasma MSI-High patients. In a cohort of 16 MSI-High gastric cancer patients treated with immune checkpoint inhibitors, the objective response rate was 63% and disease control rate was 81%, consistent with responses for patients identified by tissue testing.
The validation of Guardant360’s MSI detection methods is an important achievement in the development of liquid biopsy technology. Chromosomal positions most often associated with MSI are made up of highly repetitive genomic sequences. Because circulating tumor DNA (ctDNA) fragments are generally much shorter than tissue-derived tumor DNA, accurately mapping these fragments to the genome required innovations in panel design, DNA capture, and bioinformatics analysis.
“Millions of microsatellites exist throughout the genome, but most of them are poorly suited for blood-based clinical genomic analysis,” said Scott Kopetz, MD, PhD, Associate Professor of Gastrointestinal Medical Oncology at The University of Texas and co-author on the study. “These results show that a carefully designed panel, combined with efficient DNA-capture biochemistry and sophisticated bioinformatics tools, allow for accurate, sensitive MSI detection.”
“We are proud to be able to bring this innovation to Guardant360 ordering physicians and the patients they treat,” said AmirAli Talasaz, PhD, Guardant Health Co-Founder and President. “We remain committed to improving the performance and utility of our products as our lab and the broader oncology field achieve advances in technology and breakthroughs in treatment.”
About Guardant Health
Guardant Health is a leading precision oncology company focused on helping conquer cancer globally through use of its proprietary blood tests, vast data sets and advanced analytics. Its Guardant Health Oncology Platform is designed to leverage its capabilities in technology, clinical development, regulatory and reimbursement to drive commercial adoption, improve patient clinical outcomes and lower healthcare costs. In pursuit of its goal to manage cancer across all stages of the disease, Guardant Health has launched multiple liquid biopsy-based tests, Guardant360 and GuardantOMNI, for advanced stage cancer patients, which fuel its LUNAR development programs for recurrence and early detection. Since its launch in 2014, Guardant360 has been used by more than 6,000 oncologists, over 50 biopharmaceutical companies and all 28 of the National Comprehensive Cancer Network centers.
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