Background Tumor lysis syndrome results when intracellular contents are released during cell lysis. Ibrutinib, a Bruton tyrosine kinase inhibitor, is used for the treatment of chronic lymphocytic leukemia, small lymphocytic lymphoma, Waldenström's macroglobulinemia, mantle cell lymphoma, and marginal zone lymphoma. Tumor lysis syndrome caused by ibrutinib therapy is potentially life threatening, but is rare and not often reported in clinical trials. Objective The purpose of this case series is to describe the occurrence of tumor lysis syndrome in two patients initiated on ibrutinib, and to highlight the importance of close monitoring during therapy. Discussion One patient with chronic lymphocytic leukemia/small lymphocytic lymphoma and one patient with mantle cell lymphoma developed laboratory and clinical tumor lysis syndrome following initiation of ibrutinib therapy. Assessment with the Naranjo Adverse Drug Reaction Probability Scale indicated one probable relationship and one possible relationship between ibrutinib therapy and tumor lysis syndrome. There were additional factors that may have confounded the laboratory and clinical factors observed, including baseline laboratory values and concurrent medications. Both patients were managed with supportive therapies. A literature review identified five additional reported cases of tumor lysis syndrome following ibrutinib therapy. Conclusion This case series identifies one patient with a probable relationship and one patient with a possible relationship between the development of tumor lysis syndrome and treatment with ibrutinib. Although uncommon, proper attention should be given to monitoring for this adverse drug reaction and appropriate follow-up should occur despite ibrutinib's ease of administration.
Keywords: Bruton tyrosine kinase inhibitor; ibrutinib; medication safety; tumor lysis syndrome.