Cyclophosphamide desensitization in patients with severe hypersensitivity reactions to bendamustine

Introduction: Cyclophosphamide is a nitrogen mustard alkylator employed in the treatment of many malignancies and autoimmune disorders. Despite reports of cyclophosphamide hypersensitivity ranging from rash to anaphylaxis, no cases of desensitization have been reported in the oncologic setting. Case report: We report a cyclophosphamide desensitization protocol used for two patients who experienced severe hypersensitivity to bendamustine, a structurally related drug with potential cross immunogenicity. Management and outcome: An interdisciplinary approach including immunologist, oncologist, and clinical pharmacists resulted in the development of a multi-step desensitization protocol for cyclophosphamide. The desensitization protocol described enabled the safe administration of cyclophosphamide for the two patients with limited treatment alternatives. Discussion: To the authors' knowledge, this is the first report of cyclophosphamide desensitization in the oncologic setting. Two patients with advanced hematologic malignancies were able to receive cyclophosphamide with minimal adverse effects, despite experiencing previous severe hypersensitivity to another nitrogen mustard analogue.