In May, the FDA approved pembrolizumab in any unresectable or metastatic tumor with mismatch repair deficiency or microsatellite instability.
These are terms to describe mutations found in some tumors that prevent your body’s cells from repairing errors in DNA copy. This leads to instability and tumor growth. The most common tumor types where we find mismatch repair deficiencies are in colon cancer and endometrial cancer; however, these mutations can be rarely seen in many other tumor types as well.
Recently, a trial showed that patients with these mutations that had progressed on prior chemotherapy had up to a 40% response rate and most responses were durable for over a year. It is now very important that each patient’s cancer be tested for these molecular mutations to see if this is a tumor that may respond to pembrolizumab. At HOAA, we have been testing for these mutations for a couple of years already so hopefully we do not miss an opportunity to find a new treatment option for our patients.