(C-072) Treatment Patterns of Immunoglobulin Replacement Therapy Among Patients with Multiple Myeloma in the United States: a Real-World Analysis

Background: Hypogammaglobulinemia (HGG) is defined as low (≤7 g/L) serum immunoglobulin (Ig) G, with IgG < 4 g/L often referred to as secondary immunodeficiency (SID). Patients (pts) with relapsed/refractory multiple myeloma (RRMM) are at risk of SID related to underlying disease and/or B-cell depletion, and are at greater risk of frequent and severe infections. Ig replacement therapy (IgRT) can be used to mitigate this risk; however, guidelines for IgRT use vary widely.

Objectives: This retrospective cohort study aimed to assess patterns of IgRT use in pts with RRMM across the United States (US).

Methods: This study used the US Optum Market Clarity database (data available 10/2015–9/2023), to assess outcomes in pts ≥18 years with RRMM (ICD-10 codes C90.00 and C90.02). Pts were excluded if they had history of non malignant conditions indicated for IgRT prior to MM diagnosis, or fewer than 6 months of baseline data pre-index, defined as date of incident or prevalent RRMM diagnosis. Variables of interest included baseline pt characteristics, cancer therapies, IgG levels, and patterns of IgRT use. The follow-up period (FU) began 1 day after RRMM diagnosis, ending at the earliest of: end of observability or study period, or death.

Results: A total of 43,793 pts were included. In the baseline 6-month data period, mean (standard deviation [SD]) age was 66.4 (12.0), 44.6% (n=19,533) of pts were male, and 57.1% (n=25,001) were Caucasian. Overall, 10.1% (n=4,409) had history of other heme malignancies, 11.0% (n=4,819) had any grade of neutropenia, and 3.6% (n=1,588) had documented SID. A total of 20.1% (n=8,798) had evidence of baseline IgG lab results. Only 1.2% (n=516) of pts received IgRT, 8.4% (n=3,694) received prophylactic antibiotics and 30.8% (n=13,497) had been vaccinated.
During FU, immunomodulatory drugs were used in 31.7% (n=13,861) pts, IgG lab results were available for 30.1% (n=13,183) and IgG < 4g/L observed in 11.7% (n=1,541).
Overall, 4.1% (n=1,789) of pts (n=43,793) were treated with IgRT post-RRMM diagnosis; 2.8% (n=1,232) received IVIG, 0.1% (n=30) received SCIG, and IgRT administration route was unknown for 1.2% (n=527). The median (interquartile range) time from RRMM diagnosis date to IgRT initiation was 276.0 (63.0, 712.5) days. In FU, 9,001 pts (20.6%) received prophylactic antibiotics, 17,775 (40.6%) had prophylactic antivirals and 23,609 (53.9%) had vaccinations.
Among 42,930 pts without IgRT prior to RRMM diagnosis, infections were experienced by 37.7% (n=16,200) of pts, with 14.3% (n=6,131) experiencing serious bacterial infections in FU.

Conclusions: This study suggests suboptimal IgG testing and IgRT use compared with expectations based on guidelines, and a need to raise awareness of using IgRT to manage SID in pts with RRMM at risk of infections.