Neoadjuvant anti PD-1 / PD-L1 immune checkpoint inhibitors in locally advanced gastric cancer with microsatellite instability

Gastric cancer is an aggressive malignant neoplasm of the digestive system. These tumors are genetically heterogeneous,and they could be subdivided into four groups. One of such groups, microsatellite instable (MSI) gastric cancer, is of interest considering prognosis and response to therapy. Immune checkpoint inhibitors present a perspective strategy in treating these tumors, however, there is currently insufficient data on their use in microsatellite instable gastric cancer. Aim of this study was to evaluate objective response to neoadjuvant checkpoint inhibitors treatment in patients with MSI gastric cancer. Eleven patients were enrolled. They received Nivolumab or Pembrolizumab (investigator choice) in a neoadjuvant setting. Objective response was registered in 9 (81,8%) patients, two patients had stabilization. Nine patients (81,8%) underwent radical surgery. Pathologic complete response (pCR) was registered in 3 (33,3%). Postoperative complications were tracked and registered in accordance with Clavien-Dindo classification: grade 1 – 2 patients, grade 2 – 2 patients, grade 3 – 1 patient.