P-121: Healthcare resource utilization and morbidities in patients with idiopathic Multicentric Castleman Disease

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<h3>Background</h3> Human herpesvirus-8-negative/idiopathic multicentric Castleman disease (iMCD) is a heterogeneous group of diseases characterized by a proinflammatory hypercytokinemic state with a wide range of systemic manifestations ranging from generalized lymphadenopathy to death in severe cases. Limited data have shown increased prevalence of organ dysfunction and cancers in iMCD patients. The objective of this study was to assess healthcare resource utilization and patterns of iMCD-related morbidities in a real-world setting. <h3>Methods</h3> Retrospective analysis of administrative claims for <i>~</i>31 million US patients enrolled from 1/1/2017-12/31/2019. Patients were identified as iMCD if they had an ICD-10 code for Castleman disease (CD) and ≥2 codes corresponding to minor criteria from the iMCD consensus diagnostic criteria. Exclusion criteria were history of HIV or HHV-8. Index diagnosis date (IDD) was defined as the first time a patient received a diagnosis for CD using the new ICD-10 code (D47.Z2) or the general ICD-9 code for lymphadenopathy (785.6) that included CD, whichever was diagnosed first between 2006 and 2019. Included patients were followed for up to 5 years from IDD. <h3>Results</h3> We identified 271 iMCD patients, 161 women (59%) and 110 men (41%), mean age 51 years (range: 6-90). Average post-diagnosis follow up was 2.8 years after IDD (range: 0.3-14.1). Within first year of iMCD diagnosis, 49.1% of patients required inpatient hospitalization and 54.6% had at least one emergency room visit. Over a five-year period following initial iMCD diagnosis, patients had an average annual hospitalization rate and emergency room visit rate of 23.9% and 30.5%, respectively. The annual rate of hospitalizations and emergency room visits for the entire database of <i>~</i>31 million patients were 9.0% and 20.6%, respectively. The average annual prevalence of morbidities in the iMCD cohort (vs. prevalence in entire database) was 5.7% (vs. 0.3%) for hematologic malignancies, 4.6% (vs. 2.5%) for non-hematologic malignancies, 3.9% (vs. 0.6%) for thromboses, 2.6% (vs. 0.6%) for renal failure, and 1.9% (vs. 0.5%) for respiratory failure. Based on an average annual iMCD incidence of 3.1 (95% CI, 1.2-9.0) cases per million and average prevalence of 9.7 (95% CI, 5.3-18.6) cases per million, we estimated the average duration of documented disease as 3.1 years after diagnosis. <h3>Conclusion</h3> We found a high rate of hospitalizations, emergency room visits, organ dysfunction, and malignancy in the five years following iMCD diagnosis, compared to the general population. The average duration of documented disease was 3.1 years, which may reflect a combination of poor survival, changes in health insurance, miscoding, or resolution of symptomatic disease. Further studies are needed to compare outcomes to age-matched controls and determine whether these adverse outcomes are broadly seen across iMCD patients or instead attributable to a smaller subset of more severe cases.