Infection Burden and Survival Outcomes in Multiple Myeloma Patients with Acquired Hypogammaglobulinemia Receiving Antibiotic Prophylaxis without IVIG: A Single-Center Real-World Study

Infections remain one of the leading causes of morbidity and mortality in patients with multiple myeloma (MM), particularly during the first three months following diagnosis. This study specifically aimed to evaluate the infection burden and survival outcomes in MM patients with acquired hypogammaglobulinemia receiving antibiotic prophylaxis alone. This retrospective single-center study included 22 MM patients diagnosed with acquired hypogammaglobulinemia between January 2020 and December 2022. Hypogammaglobulinemia was defined as IgG < 500 mg/dL (excluding paraproteins). Patients received levofloxacin prophylaxis for the first 3 months after diagnosis, followed by trimethoprim/sulfamethoxazole and valacyclovir throughout the treatment process. The median age was 66.9 years (range: 53-88), and 63.6% of patients were ≥65 years old and 59.1% of the patients were male. A total of 43 infections were recorded, with pneumonia being the most common (30.2%). Only 4 patients (18.2%) required hospitalization due to infection, and 2 patients (9.1%) had neutropenia during the infection period. The median overall survival (OS) was 22 months (range: 1-85), with 7 deaths (31.8%) recorded, and only 1 (4.5%) was infection-related. Patients with light chain myeloma had a higher incidence of infections compared to other myeloma types (p= 0.02). Hospitalization due to infection was associated with shorter OS (p= 0.002). Our findings suggest that antibiotic prophylaxis may help limit severe infections and infection-related mortality in MM patients with hypogammaglobulinemia, particularly in the early phase of treatment. Further studies are warranted to determine optimal prophylactic strategies in this high-risk subgroup. Keywords: Multiple Myeloma, Hypogammaglobulinemia, Antibiotic Prophylaxis, Levofloxacin, IVIG Replacement