BACKGROUND: Pembrolizumab is associated with the development of gastritis, but its clinical features have not been characterized. To explore the clinical features of pembrolizumab induced gastritis and provide reference for the prevention and treatment of gastritis.
METHODS: Case reports and case series related to pembrolizumab induced gastritis were retrospectively analyzed by searching the database from inception to September 30, 2023.
RESULTS: Thirty-nine patients with gastritis entered the study with a median age of 63 years (range 34, 81). The median time to gastritis was 11.1 months (range 0.3, 60) and 7 cycles (range 1, 27) after administration. Epigastric pain (24 cases, 61.5%), nausea (17 cases, 43.6%), and vomiting (16 cases, 41.0%) were the most frequently complained symptoms. Esophagogastroduodenoscopy mainly showed erythematous (16 cases, 41.0%), hemorrhage (14 cases, 35.9%) and erosions (11 cases, 28.2%). Gastric mucosal biopsy shows chronic active gastritis with lymphocytic infiltration. These patients\' symptoms and gastric mucosa improved or recovered after receiving systemic steroid and proton pump inhibitor therapy regardless of whether pembrolizumab was discontinued. These patients\' symptoms and gastric mucosa improved or recovered after treatment with systemic steroids, proton pump inhibitors, and biological agents.
CONCLUSIONS: Gastritis is an extremely rare adverse effect of pembrolizumab. When patients receiving pembrolizumab complain of abdominal symptoms, endoscopy, tissue biopsy, and immunohistochemical staining should be actively performed for early identification and diagnosis of gastritis.

Gastritis has recently been reported to be associated with nivolumab, and the clinical characteristics of nivolumab induced gastritis remain unclear. To explore the clinical characteristics of nivolumab induced gastritis, and to provide reference for the classification and treatment guidelines of immune checkpoint inhibitors -related gastritis. Case reports, case series, and clinical studies of nivolumab induced gastritis were retrospectively analyzed by searching the database from the establishment of the database until September 30, 2023. Forty-seven were included, with a median age of 57 years (range 16, 93). The median time of symptom onset was 6 months (range 0.5,36) and 6.5 cycles (range 2, 62). Nausea (29 cases, 61.7%), vomiting (29 cases, 61.7%), and epigastric pain (28 cases, 59.6%) were the most common complaints. Esophagogastroduodenoscopy mainly showed erythema (28 cases, 59.6%). Gastric mucosa biopsy showed epithelial inflammatory cell infiltration (22 cases, 46.8%) and apoptosis (15 cases, 31.9%). Most patients\' symptoms and gastric mucosa improved or recovered after receiving systemic steroid and proton pump inhibitor therapy regardless of whether nivolumab was discontinued. Two patients died from gastritis related events. Gastritis should be considered as the cause of unexplained epigastric symptoms in the administration of nivolumab. Understanding the clinical features of nivolumab induced gastritis is very important for accurate diagnosis and timely management of these patients.

Pembrolizumab is an immune checkpoint inhibitor that induces side effects called \"immune-related adverse events\" (irAEs). Various types of organs are affected by irAEs, although reports of upper gastrointestinal disorders are rare. Here, we report a case of extensive inflammatory pathologies in the oesophagus, stomach, duodenum, and jejunum after the administration of pembrolizumab for non-small cell lung cancer.