Successful immunotherapy with PD-1 Iinhibitor for advanced pancreatic cancer: report of two cases and review of literature.

Pancreatic cancer is a highly malignant tumor, and most patients are diagnosed at an advanced stage. Unfortunately, due to the immunosuppressive tumor microenvironment of pancreatic cancer, the benefits of immunotherapy for patients with advanced pancreatic cancer are still unclear. Here, we present two cases of advanced pancreatic cancer being controlled by immunotherapy, with pathological diagnoses of ductal adenocarcinoma and acinar cell carcinoma, respectively. Next-generation sequencing (NGS) of both patients is high tumor mutation burden (tumor mutation burden-High) and microsatellite stable. The patient with pancreatic ductal adenocarcinoma was diagnosed as a locally advanced disease (stage III). She received irreversible electroporation, used the programmed death receptor-1 (PD-1) inhibitor (pembrolizumab) combined with chemotherapy (S-1), and then used only the PD-1 inhibitor as a maintenance treatment. As a result, the patient's lesion was significantly reduced, with a partial response time of up to 31 months. The patient with acinar cell carcinoma was diagnosed as a metastatic disease (stage IV), next-generation sequencing revealed mutations in SMAD4 and KMT2D, and two chemotherapy regimens were used unsuccessfully. Then, the combination of chemotherapy with PD-1 (tislelizumab) and vascular endothelial growth factor/vascular endothelial growth factor receptor (anlotinib) inhibitors were used, and the lesions of the patient were significantly reduced, and the progression-free survival after immunotherapy was 19 months. In advanced pancreatic cancer, a prognosis of this magnitude is rare. Our cases reveal the potential of immunotherapy as a cornerstone treatment in the management of advanced pancreatic cancer.