Immune thrombocytopenia in a small cell lung cancer patient treated with atezolizumab: a case report

Background: Immune checkpoint inhibitors (ICIs), an enormous oncological breakthrough in the last 10 years, have become the standard treatments for several types of solid cancers. Although ICIs are generally well tolerated and result in favorable outcomes, they also cause unique immune-related adverse events (irAEs) across bodily systems and organs. Compared to most common irAEs, which occur in the endocrine, skin, pulmonary system, and gastrointestinal tract, haematological irAEs (haem-irAEs) are relatively rare but potentially life-threatening events that are occasionally irreversible and refractory. Currently, haem-irAEs are not sufficiently understood, management, and lack consensus, while other common irAEs have well been characterized and managed. The reports of ICI-related thrombocytopenia in small cell lung cancer (SCLC) are rarely seen. Hence, we reported a rare case of severe steriod-resistant ICI-related thrombocytopenia after received chemotherapy plus anti-PD-L1 inhibitor in SCLC patient. Our case exemplifies the diagnosis, diagnosis of exclusion, treatment, and prognosis of thrombocytopenia in the pattern of combination therapy, meanwhile, the subject of diagnosis, therapies, therapeutic strategies for refractory type and incidence, potential biomarkers, mechanisms and prognosis in ICI-related thrombocytopenia have been fully discussed.Case Description: Herein, we present a 64-year-old man diagnosed advanced SCLC developed refractory immune-related severe thrombocytopenia, who achieved favorable outcomes of cancer following chemotherapy combined with atezolizumab administrated. Routine blood re-examination on the third day of 6th therapy showed a thrombocyte count of 11x109/L. Combined the medical history and the results of laboratory tests, the diagnosis of ICI-induced thrombocytopenia was confirmed. Despite large doses of methylprednisolone, immunoglobulin, and rituximab, intermittent platelet transfusion, thrombopoietin being administrated to the patient, there were no signs of platelet count and hemoglobin improvement. Currently, this is the first case about atezolizumab induced thrombocytopenia in SCLC patient, while there is extremely rare haem-irAEs reported in SCLC. Conclusions: Although ICI-related severe thrombocytopenia is rare, it may persist or even be fatal. Clinicians should pay more attention to its diagnosis and prompt treatment. Once developed thrombocytopenia, large doses of methylprednisolone, ntermittent platelet transfusion, thrombopoietin should be timely administrated, also plasma exchange or rilzabrutinib, other immunosuppressive drugs, or IL-6 inhibitor warrant apply if steriod-resistant.