Microsatellite Instability Serves as a Predictive Biomarker of Response to Pembrolizumab

Joseph Chao, MD, discusses the importance of assessing the microsatellite instability (MSI) status in patients with advanced gastric/gastroesophageal junction cancer based on findings from a comparative analysis of KEYNOTE-059, KEYNOTE-061, and KEYNOTE-062.

Joseph Chao, MD, assistant professor of Medical Oncology Research at the City of Hope, discusses the importance of assessing the microsatellite instability (MSI) status in patients with advanced gastric/gastroesophageal junction (GEJ) cancer based on findings from a comparative analysis of KEYNOTE-059, KEYNOTE-061, and KEYNOTE-062.

The prognosis for patients with stage IV gastric/GEJ cancer is fairly poor, Chao says. With the current treatment landscape, however, patients with MSI-high disease who receive treatment with a PD-1 inhibitor, such as pembrolizumab (Keytruda), have a vastly improved prognosis.

Based on the data from this analysis, which Chao presented at the 2020 American Society of Clinical Oncology (ASCO) Gastrointestinal (GI) Cancers Symposium, MSI-high patients who do not receive PD-1 inhibition therapy have a fairly poor prognosis. Therefore, it is important to look for MSI status as a predictive biomarker for treatment with pembrolizumab.

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