Infection Outcomes and Hypogammaglobulinemia in Patients with Chronic Lymphocytic Leukemia Treated with Immunoglobulin Replacement Therapy

INTRODUCTION: Hypogammaglobulinemia (HGG), a secondary immunodeficiency (SID), can manifest in patients with chronic lymphocytic leukemia (CLL) due to the disease and its treatments. Up to half of all deaths from CLL are attributed to infection; however, use of immunoglobulin replacement therapy (IgRT) for the prevention of infections in selected patients varies. We aimed to assess real-world IgRT utilization and infection outcomes in patients with CLL.

METHODS: A retrospective, longitudinal study evaluating real-world IgRT use in adult patients with CLL diagnosed after 2010, with ≥ 3 visits/year and ≥ 12 months of clinical data, was conducted. De-identified clinical data came from the Massachusetts General Brigham Research Patient Data Registry. Immunoglobulin G (IgG) testing, infection outcomes, and antimicrobial use were compared before versus after IgRT initiation. Generalized estimating equation logistic regression models calculated odds ratios (ORs), 95% CIs, and P-values.

RESULTS: Of 3960 patients with CLL assessed, 2652 (67.0%) patients had IgG testing (29.0% tested at CLL diagnosis); 917 (34.6%) had HGG (IgG level < 500mg/dL). Median (interquartile range [IQR]) age was 68.0 (60.0, 76.0) years, 61.2% were men, 67.8% were treatment-naïve, and median (IQR) follow-up duration was 4.8 (2.4, 7.4) years. Among recipients of IgRT (n = 259), 56.8% received ≥ 2 administrations and the median (IQR) number of IgRT administrations was 2.0 (1.0, 4.0). Median (IQR) time from CLL diagnosis to IgRT initiation was 38.0 (11.4, 64.7) months. Significantly fewer patients had HGG 3 months after IgRT versus 3 months before (33.8% vs 72.8%; P < 0.0001). Significantly lower odds of infections and antimicrobial use were observed after IgRT initiation in 3- and 6-month time periods for: all infections, sinopulmonary and skin or soft tissue infections, infections requiring antimicrobials, all severe infections, severe sinopulmonary and skin or soft tissue infections, and severe infections requiring antimicrobials (Table).

CONCLUSIONS: In this real-world study of patients with CLL, IgRT was associated with significant reductions in HGG, infection rates, and infections requiring antimicrobials. Guidelines are needed to optimize IgG testing, IgRT initiation, and SID management for patients with CLL.