Dr. Jones on the Importance of Testing for Microsatellite Instability in CRC

Jeremy C. Jones, MD, hematologist/oncologist, Mayo Clinic, discusses the importance of testing for microsatellite instability high (MSI-H) in colorectal cancer (CRC).

All patients with CRC, including those without metastatic disease, should undergo molecular testing to determine MSI-H status, says Jones. Testing is commonly performed by immunohistochemistry or polymerase chain reaction assays, Jones adds.

Although MSI-H tumors account for approximately 5% of all CRC, this patient subgroup has demonstrated dramatic response rates with checkpoint inhibitor therapy, Jones explains. As such, it is critical to ensure patients with MSI-H CRC are appropriately identified and treated with checkpoint inhibitors, such as pembrolizumab (Keytruda), concludes Jones.