Abstract
The incidence rate of pseudoprogression during immune checkpoint inhibitor monotherapy for non-small cell lung cancer is reportedly 3.6%-6.9%, while pseudoprogression during chemoimmunotherapy is rare. Reports on pseudoprogression during dual immunotherapy combined with chemotherapy are lacking. Herein, a 55-year-old male with invasive mucinous adenocarcinoma (cT2aN2M1c [OTH, PUL], stage IVB, and programmed death-ligand 1 expression <1%), renal dysfunction, and disseminated intravascular coagulation was treated with carboplatin, solvent-based paclitaxel, nivolumab, and ipilimumab. After treatment initiation, computed tomography (CT) on day 14 showed disease progression. The patient was diagnosed with pseudoprogression because of a lack of symptoms, improved platelet count, and decreased fibrin/fibrinogen degradation product levels. CT on day 36 showed a reduction in the primary lesion size, multiple lung metastases, and mesenteric metastases. Therefore, pseudoprogression should be considered during dual immunotherapy with chemotherapy.