Infection Incidence, Timing, and Predictors in Newly Diagnosed Multiple Myeloma: A Real- World Retrospective Cohort Study

Background: Infections are a leading cause of morbidity and mortality in multiple myeloma (MM), particularly during the induction phase. Identifying real-world infection patterns and predictors is crucial for guiding preventive strategies. Methods: This retrospective cohort study included 161 newly diagnosed MM patients who received standard induction therapy at a single tertiary center between 2016 and 2024. Clinical, laboratory, and infection-related parameters were analyzed over the first 12 months. Results: Infections occurred in 50.9% of patients, with the highest incidence within the first 3 months (27.3%, p = 0.004). Pneumonia was the most common type (34.1%), and gram-negative bacteria, particularly Escherichia coli , Klebsiella spp. , and Pseudomonas aeruginosa , were predominant. Antibiotic resistance to TMP-SMX and levofloxacin was observed in E. coli isolates. Multivariate analysis identified advanced ISS stage (OR: 3.83), diabetes mellitus (OR: 3.64), and chronic kidney disease (OR: 6.01) as independent predictors of infection ( p < 0.05). Lymphocyte counts were significantly lower in febrile episodes ( p = 0.040), highlighting a possible early immune marker. Hospitalization was more common in patients with advanced ISS and kidney disease. No significant differences were found between induction regimens. Conclusion: Infections pose a significant burden during the first year of MM treatment, particularly in high-risk patients during early induction. Readily available clinical parameters can aid in early risk stratification. These findings support a risk-adapted approach to prophylaxis, including the selective use of levofloxacin in patients with diabetes or kidney disease during the first 3 months of therapy.