Epidemiology of bloodstream infections in patients with myeloma receiving current era therapy.

BACKGROUND: Bloodstream infections (BSIs) are a significant complication of treatment for multiple myeloma (MM). The objective of this study was to define the epidemiology of BSI with current era MM treatment regimens, including immunomodulatory drugs, proteasome inhibitors and autologous haematopoietic stem cell transplantation (ASCT).

METHODS: Clinical and microbiology records of patients with MM diagnosed between 2008 and 2012 were reviewed using a standardised tool to capture patient demographics, myeloma characteristics and BSI characteristics (type, severity, outcomes). Conditional risk set modelling was used to determine clinical predictors of BSI.

RESULTS: Of 199 studied patients, 71 (35.6%) had confirmed BSI (98 infection episodes). Peak incidence was 65.1 infections/100 patient-years at 4-6 months following MM diagnosis with a late peak at 64-66 months. Gram-positive pathogens were responsible for the majority (54.5%) of infections during induction, whilst gram-negative pathogens were responsible for the majority (57.7%) of infections during disease progression. Overall, Escherichia coli was the most frequently identified pathogen. Streptococcus pneumoniae comprised 6.1% of all BSIs at a median of 7.5 months following MM diagnosis. Highest rates of ICU admission (23.1%) and mortality (11.5%) were seen with BSIs in patients with progressive disease. Recent ASCT was independently associated with increased BSI risk (HR 3.09, P = 0.05).

CONCLUSIONS: Treatment of progressive disease is a high-risk period for infection, evidenced by high proportions of BSI due to gram-negative pathogens and S. pneumoniae. Targeted evaluation of preventative strategies (prophylaxis, vaccination) to reduce morbidity and mortality during this period is required.