Risk of Hematologic Malignancies in Elderly Patients With Ankylosing Spondylitis: A Cohort Study and Systematic Review

Abstract

ObjectiveTo examine the risk of hematologic malignancies in older adults with ankylosing spondylitis (AS). Patients and MethodsWe used US Medicare data from January 1, 1999, to December 31, 2010, to identify a population-based cohort of beneficiaries with AS. We also included beneficiaries with inflammatory bowel disease (IBD) as disease controls and beneficiaries without AS or IBD as unaffected controls. We excluded those treated with tumor necrosis factor inhibitors in this period. We followed up each group for new diagnosis claims for hematologic malignancies until September 30, 2015. ResultsWe included 12,451 beneficiaries with AS, 234,905 with IBD, and 10,975,340 unaffected controls, with a mean follow-up of 9.9, 9.3, and 8.0 years, respectively. We identified 297 hematologic malignancies in the AS group, 4538 malignancies in the IBD group, and 128,239 malignancies in unaffected controls. The standardized incidence ratio in AS vs unaffected controls was 1.39 (95% CI, 1.05 to 1.61) for non-Hodgkin lymphoma, 1.50 (95% CI, 1.17 to 1.92) for chronic lymphocytic leukemia, and 1.52 (95% CI, 1.12 to 2.06) for multiple myeloma. Risks of acute myeloid leukemia and chronic myeloid leukemia were not elevated in AS, and there were too few cases of Hodgkin lymphoma to compute risks. Risks were comparable to those of beneficiaries with IBD. We also performed a systematic literature review of the risk of hematologic malignancy in AS, focusing on age associations, which have not been previously examined. We identified 21 studies in the systematic literature review, which included mainly young or middle-aged patients. Results suggested that AS was largely not associated with an increased risk of hematologic malignancies. Two cohort studies reported an increased risk of multiple myeloma in AS. ConclusionThe risks of non-Hodgkin lymphoma, chronic lymphocytic leukemia, and multiple myeloma are increased among elderly patients with AS.