Checkpoint inhibitors in the treatment of metastatic MSI-H pancreatic cancer: own experience of durable disease control

Microsatellite instability (MSI) is the molecular phenotype resulting from a deficient DNA mismatch repair (MMR) system. This deficiency has a superior diagnostic, prognostic, and predictive value for treatment outcomes in patients with different types of cancer. There is growing interest in this genetic variation due to high MSI/dMMR tumor response rates in patients receiving cancer immunotherapy drugs. Immune checkpoint inhibitors improve cancer outcomes in patients with advanced MSI solid tumors. However, the incidence of MSI-H in patients with pancreatic adenocarcinoma appears to be extremely low (1–2%), and experience with the use of this drug class in this patient cohort is limited. The case presented in this article illustrates a durable response to immunotherapy (over 12 months) with disease control in a patient with locally advanced unresectable MSI-H pancreatic cancer after changing a treatment regimen due to grade 3-4 gastrointestinal toxicity during standard first-line chemotherapy. This observation shows the advantage of determining MSI status and using PD-1 inhibitors in patients with this nosology entity.