Severe Thrombocytopenia Associated With Pembrolizumab in Patients With Non-small Cell Lung Cancer (NSCLC): A Case Report and Literature Review

Background/Aim: Thrombocytopenia, one of many immune-related adverse events (irAEs), is a rare entity about which little is known on its treatment, outcomes, and patient demographics. Herein we present a case of severe thrombocytopenia after administration of pembrolizumab as an anti-programmed death-1 (PD-1) antibody. Case Report: A 66-year-old man with advanced non-small cell lung cancer (NSCLC) received pembrolizumab; 21 days later, his platelet count was progressively decreased and he experienced severe thrombocytopenia (grade 4; platelet count 0.4x10(9)/l). With oral steroids 1 mg/kg/day, the platelet count improved sufficiently; thus, a definite diagnosis of severe irAE-related thrombocytopenia was performed. Conclusion: Several reports have described the management and occurrence of severe thrombocytopenia after immune checkpoint inhibitor administration in patients with different neoplasms. Physicians should be alert to the potential of rare irAEs, such as severe thrombocytopenia.