Estimating the Healthcare Cost of Infection-Related Hospitalisations in Multiple Myeloma

The purpose of this study was to estimate and predict the cost of infection-related hospitalisations and infection prevention using immunoglobulin replacement therapy (IgRT) in patients with multiple myeloma (MM), and to explore how patient factors, treatment and comorbidities influence healthcare costs, excluding patient and societal costs.

This was a retrospective analysis of linked longitudinal data from the Victorian Admitted Episode Data, Victorian Cancer Registry, Victorian Death Index and Victorian Cost Data Collection. The cohort included patients with MM hospitalised for any cause between July 2016 and June 2022. A generalised linear model with gamma distribution and identity link was used to estimate the excess cost related to having an infection-related hospitalisations and comorbidities, controlling for age, sex, Charlson Comorbidity Index (CCI), time from diagnosis, anti-cancer treatment, chronic comorbidities, IgRT and death. Clustered standard errors were used to account for multiple observations per patient. Costs were adjusted to 2024 Australian dollars (AU $) using the Australian Bureau of Statistics medical/hospital services consumer price index. Estimated costs were used to predict total costs for different scenarios.

The study included 5857 patients with MM; 58.2% were male, 64.7% were aged over 65 years, and 57.9% had mild comorbidities (CCI of 1-2). The incidence of infection-related hospitalisations averaged 0.8 per patient-year. The mean in-hospital cost was highest in the month of diagnosis (AU $8107). The total excess in-hospital costs associated with an infection-related hospitalisations per patient in the index month and the 6 months after the infection were significantly different in patients with cardiovascular disease, chronic liver disease and chronic lung disease (AU $32,139, AU $30,600 and AU $22,006, respectively) compared with patients without these comorbidities (AU $25,285). The annual cost associated with continuous monthly administration of IgRT was AU $34,049 per patient, assuming 12 treatment episodes per year. On the basis of offsetting hospital costs (excluding potential impacts on minor infections, infection severity, mortality or quality of life), 1 year of continuous IgRT would need to prevent at least 1.2 infection-related hospitalisations per patient per year to offset its cost.

In patients with MM, infection-related hospitalisation and IgRT are associated with a substantial economic burden. The financial burden of treating infection-related hospitalisations differed in the presence of coexisting chronic comorbidities in patients with MM.