Hematologic complications of immune checkpoint inhibitors

Immune checkpoint inhibitors are a class of antineoplastic therapies that unleash immune cells to kill malignant cells. There are currently 7 medications that have been approved by the US Food and Drug Administration for the treatment of 14 solid tumors and 2 hematologic malignancies. These medications commonly cause immune-related adverse effects as a result of overactive T lymphocytes, autoantibody production, and/or cytokine dysregulation. Hematologic toxicities are rare and of uncertain mechanism, and therefore management is often based on experiences with familiar conditions involving these perturbed immune responses, such as autoimmune hemolytic anemia, immune thrombocytopenia, and idiopathic aplastic anemia. Management is challenging because one must attend to the hematologic toxicity while simultaneously attending to the malignancy, with the imperative that effective cancer therapy be maintained or minimally interrupted if possible. The purpose of this review is to help clinicians by providing a clinical and pathophysiological framework in which to view these problems.