Epidemiology and Outcomes of Hospitalizations Due to Waldenstrom Macroglobulinemia: A National Perspective

Introduction:Waldenstorm's macroglobulinemia (WM) is a type of indolent B cell lymphoma characterized by immunoglobulin M monoclonal gammopathy and bone marrow infiltration by lymphoplasmacytic cells. Being an uncommon hematologic malignancy, studies on epidemiology of this disease are limited. Median survival is 5-11 years and depends on disease progression, treatment complication and transformation to high-grade lymphoma. In the nationally representative database, we aimed to find out the trends and outcomes of hospitalizations primarily due to WM.

Methods:We used National Inpatient Sample (NIS) for the years 2007-2017 by Healthcare Cost and Utilization Project. We extracted a study cohort of adult hospitalizations due to WM using International Classification of Diseases (9th/10th editions) Clinical Modification diagnosis codes. Our primary and secondary objectives were to estimate the trends of hospitalization and outcomes as well as identify predictors of poor outcomes. Poor outcomes were defined as in-hospital mortality and discharge to facility. We utilized Cochran Armitage trend test and multivariable survey regression modeling to analyze trends and predictors of poor outcomes using SAS software, version 9.4 (SAS Institute, North Carolina, USA).

Results:We studied a total of 7,379 patients who were hospitalized with WM during 2007-2017. Overall from 2007 to 2017 the burden of hospitalizations has decreased from 804 to 645 . The cohort consisted of elderly patients with a median age of 69-years (IQR:61-78), 60.2% were males, 78% Caucasians, and 10.5% African American. Mean length of stay was 7-days which remained stable over the period. A decline in the proportion of WM patients being discharged to facility (20.1% in 2007 to 13.9% in 2017; pTrend<0.001) and in-hospital mortality (4.7% in 2007 to 2.3% in 2017; pTrend<0.001) was observed. Furthermore, in multivariable logistic regression analysis, rural hospitals (OR 4.3; 95%CI 1.5-12.4; p<0.001), lower median household income (OR 4.1; 95%CI 1.4-12.2; p<0.05) and concurrent conditions like septicemia (OR 10.7; 95%CI 4.2-26.7; p<0.001), and pulmonary circulatory disease (OR 3.6; 95%CI 1.4-9.1; p< 0.001) were associated with higher odds of in-hospital mortality.

Conclusion:In this nationally representative study, we observed that the hospitalizations due to WM had mildly declined and outcomes were improved during the study period which might be an indication of improvements in treatment modalities. WM in benign state is rarely a grave prognosis and does not require frequent hospitalization but mortality is usually due to other comorbidities and hyperviscosity. We were able to identify several risk predictors that were associated with poor outcomes which require further studies to better risk stratification and develop preventive measures.