Introduction: Patients with multiple myeloma (MM) have an increased risk of infection secondary to hypogammaglobulinemia, due to myeloma itself and anti-myeloma therapies. Prophylactic immunoglobulin (Ig) supplementation has been considered a potential strategy to reduce the risk of infections. A randomized controlled trial (Chapel, Lancet, 1994) demonstrated a reduction in both overall and major infections with the use of Ig. However, its real-world benefit remains unclear and prophylactic Ig is not routinely given as part of standard therapies. Furthermore, little is known regarding the routine use of Ig in the context of modern therapeutic agents such as chimeric antigen receptor T-cell (CAR-T) therapy or bispecific antibody therapies. To address this gap, we conducted an updated systematic review and meta-analysis (SRMA) to elucidate the efficacy of prophylactic immunoglobulin in patients with MM.

Methods: We performed a SRMA of observational and randomized controlled trials comparing the outcomes in patients with MM who received prophylactic immunoglobulin versus those who did not. A comprehensive search of PubMed, Scopus, and Cochrane CENTRAL databases was conducted up to July 2025, along with a manual review of the reference lists from relevant articles. This review adheres to the recommendations from the Cochrane Collaboration and the Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA) statement guidelines. R software version 4.5.1 was used for statistical analyses.

Results: A total of 18 studies were included in the systematic review. Among them, 11 studies compared patients who received immunoglobulin prophylaxis with those who did not (“Ig” versus “no Ig” groups). The remaining seven studies analyzed the same group of patients, comparing periods when they were receiving Ig (“on-Ig”) with periods when they were not (“off-Ig”). Among 18 studies, 13 studies were included in meta-analysis due to data availability (eight from the former group and five from the latter group). First, we conducted a meta-analysis of 1,234 patients from the eight studies that preceded this analysis, comparing Ig and no-Ig. Three studies included MM patients treated with bispecific antibodies, two focused on those treated with autologous stem cell transplantation (ASCT), and one on those treated with anti-CD38 antibodies. The dose of Ig was 0.4 g/kg every four weeks in most studies, and the timing of initiation of Ig varied across studies. The majority of Ig was delivered through an intravenous route. Most studies defined severe infections as those greater than grade 3 according to the Common Terminology Criteria for Adverse Events, while one study defined them as infections requiring intravenous or oral antibiotic treatment. The incidence of severe infection was significantly lower in patients who received prophylactic Ig compared with those who did not (odds ratio [OR] 0.22; 95% CI 0.08-0.63; p = 0.005). There was no significant difference in the overall infection rate between the two groups (OR 0.97; 95% CI 0.68-1.37; p = 0.85). A subgroup analysis by treatment type (chemotherapy, bispecific antibody, and ASCT) showed no significant differences in the overall infection rate among the subgroups (ASCT: OR 0.97; 95% CI 0.64-1.45; Bispecific antibody: OR 0.74; 95% CI 0.49-1.11). However, a significant reduction in the rate of severe infections was observed in patients treated with bispecific antibodies (OR 0.33; 95% CI 0.13-0.85; p = 0.021). Next, we analyzed 460 patients from the latter five studies comparing on-Ig and off-Ig. The incidence rate ratio (IRR) of overall infection was significantly lower during on-Ig periods compared with off-Ig periods (IRR 0.62; 95% CI 0.43-0.88; p = 0.0082).

Conclusions: In patients with MM, prophylactic Ig use was associated with a low incidence of severe infections. Furthermore, the incidence rate ratio of overall infection was lower during periods of Ig prophylaxis compared to periods without Ig. These findings underscore the potential efficacy of a routine Ig prophylaxis in patients with MM to mitigate the risk of infections. Since this meta-analysis does not include studies involving patients treated with CAR-T therapy, further studies are warranted to evaluate the effectiveness of Ig in patients receiving novel therapies such as CAR-T therapy, while also considering the cost and time associated with Ig administration in real-world clinical practice.

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2025
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