Prevalence and Epidemiology of Light Chain Amyloidosis in Hospitalized Multiple Myeloma Patients

Introduction/Background/Significance: Light chain (AL) amyloidosis is a relatively uncommon but clinically significant complication of multiple myeloma with important prognostic and management implications. Previous epidemiologic reports have suggested an AL amyloidosis prevalence of 10-15% in myeloma; an increased prevalence among myeloma inpatients would be expected given the frequent cardiac, renal, and neurologic manifestations that accompany AL amyloidosis. This study aims to measure the prevalence, epidemiologic associations, and hospital outcomes linked to comorbid light chain amyloidosis among patients with myeloma using a large United States inpatient database.

Materials and Methods/Case Presentation/Objective: This retrospective observational study used the Healthcare Cost and Utilization Project Nationwide Inpatient Sample (HCUP-NIS 2021). ICD-10 diagnosis codes were used to identify cohorts of inpatients within this database with AL amyloidosis, myeloma, and other clonal lymphoid/lymphoplasmacytic disorders. Associations between these disease states and nominal epidemiologic variables (race, gender, quartile of income, hospital type, hospital geographic region, primary patient insurer) were measured by logistic regression with calculation of odds ratios and with the chi-square test. Associations between disease states and quantitative variables (patient age, cost of hospitalization, length of stay) were evaluated using the rank sum test for comparing medians. Data analysis was performed using STATA software.

Results/Description/Main Outcome Measures: Inpatient cohorts of individuals with AL amyloidosis and with myeloma were identified. The prevalence of comorbid myeloma in the AL amyloidosis cohort was 40%, whereas the prevalence of comorbid AL amyloidosis among myeloma inpatients was less than 1.5%. Comorbid clonal lymphoid/lymphoplasmacytic disease other than myeloma was uncommon among AL amyloidosis inpatients (less than 3%). Among inpatients with a diagnosis of myeloma, comorbid AL amyloidosis was associated with higher median age (71 versus 67 years); was more commonly identified in teaching versus nonteaching hospitals, patients with private insurance, and in northeastern United States hospitals; and was less frequently identified in patients with Medicare insurance and in southern US hospitals. No statistically significant associations were identified among myeloma patients between comorbid AL amyloidosis and patient race, gender, or quartile of income. AL amyloidosis in myeloma patients was associated with a higher risk of inpatient death and increased median hospital charges but not with prolongation of hospital length of stay.

Conclusions: The prevalence of AL amyloidosis among myeloma inpatients in this study was significantly lower than expected from prior epidemiologic studies, likely due in part to underreporting in hospital coding. The increased prevalence of AL amyloidosis in myeloma patients in teaching hospitals may reflect patient migration to academic centers due to disease complexity and severity. However, the simultaneous positive association of comorbid AL amyloidosis with advanced age but negative association with Medicare insurance, along with geographic variations in comorbid AL amyloidosis prevalence, suggests possible underdetection among multiple myeloma inpatients in certain hospital settings. Given the need for heightened organ system assessment and multispecialty involvement, increased supportive care challenges, and variations in systemic therapy that accompany the detection of light chain amyloidosis in myeloma patients, these findings argue for increased efforts to heighten clinical awareness of AL amyloidosis in internal medicine, hospital medicine, and hematology-oncology training programs