Multiple Myeloma and Secondary Immunodeficiency: A Retrospective Database Analysis Assessing Burden of Infection and...

Patients with multiple myeloma (MM) and secondary immunodeficiency (SID) are at risk of infection-related morbidity and mortality owing to the disease process and treatment toxicity. This retrospective cohort study used anonymized data from the Optum-Humedica database (October 2015-March 2020) to assess the burden of infection in patients with MM and SID versus patients without SID. Patients aged ≥ 18 years with confirmed MM were assigned to SID and no-SID cohorts using an algorithm considering serum IgG levels < 5.0 g/L, hypogammaglobulinemia diagnosis codes, and ≥ 1 major infection. Patients with SID were stratified into those treated or not treated with immunoglobulin replacement therapy (IgRT and no-IgRT cohorts). At 12 months follow-up, a greater proportion of the SID cohort than the no-SID cohort experienced infections (58.9% vs. 31.3%; p < 0.001), severe infections (29.8% vs. 10.6%, p < 0.001), and infection-related hospitalizations (26.9% vs. 9.1%; p < 0.001). Bacterial infections were the most common infection type (SID cohort, 49.2%; no-SID cohort, 26.1%; IgRT cohort, 70.4%; no-IgRT cohort, 45.1%). Use of anti-infectives and healthcare resource utilization was higher in the SID cohort than in the no-SID cohort. Median overall survival was shorter in the SID versus no-SID cohort (12.6 vs. 14.7 months; p < 0.001) and was similar in the IgRT versus no-IgRT cohort (8.5 vs. 12.5 months; p = 0.446). Among patients with MM and SID, the higher infection burden in patients treated with IgRT than no-IgRT suggests the IgRT cohort was a more vulnerable population. A better understanding of SID burden may improve outcomes for patients with MM.