Dr. Janjigian on Conducting MSI Testing in Gastric Cancer

Yelena Y. Janjigian, MD, medical oncologist, Memorial Sloan Kettering Cancer Center, discusses when to conduct microsatellite instability (MSI) testing for patients with gastric cancer.

According to Janjigian, it is important not to wait until the last line of therapy to know a patient’s MSI status. Although data suggests a patient’s MSI status may change as the patient progresses on several lines of therapy, if a patient is MSI-high (MSI-H), they have a better chance of responding to immunotherapy, explains Janjigian.

In 2017, the FDA granted an accelerated approval to pembrolizumab (Keytruda) for the treatment of adult and pediatric patients with unresectable or metastatic MSI-H or mismatch repair deficient (dMMR) solid tumors that have progressed after prior treatment and who have no satisfactory alternative treatment options.

The approval was based on data from 149 patients with MSI-H or dMMR cancers enrolled across 5 single-arm clinical trials. The objective response rate (ORR) with pembrolizumab was 39.6% (95% CI, 31.7-47.9), including 11 (7.4%) complete responses and 48 (32.2%) partial responses.