RESUMEN
BACKGROUND: Metastatic pancreatic ductal adenocarcinoma (PDAC) is a lethal malignancy with dispiriting survival data. Immunotherapy is a promising approach to many cancer types, but achieves poor outcomes in advanced PDAC due to its immunosuppressive tumor microenvironment. We describe a case of metastatic PDAC effectively treated with pembrolizumab. CASE SUMMARY: We report the case of a 67-year-old woman with unresectable locally advanced PDAC, treated with gemcitabine plus nab-paclitaxel followed by radiotherapy plus capecitabine. At nine months, pancreatic tumor progression was observed at the level of the hepatic hilum with the appearance of a new pulmonary nodule suggestive of a second primary, confirmed by left lung biopsy. Systemic immunotherapy was then initiated with pembrolizumab, an immune checkpoint inhibitor targeting programmed cell death protein-1 that covers the two tumor types. The patient showed a complete metabolic response that was maintained throughout the treatment. The patient continues to be disease-free at 5.6 years since the start of immunotherapy. CONCLUSION: These results suggest that the administration of pembrolizumab after chemoradiotherapy has a beneficial effect in patients with metastatic PDAC. To our knowledge, this is the first reported case of a patient with metastatic PDAC and metastatic lung cancer showing such a long-lasting complete response after pembrolizumab treatment without curative surgery. Further studies are required to determine biomarkers that identify PDAC patients most likely to benefit from this immunotherapy.