Introduction
Acute lymphoblastic leukemia (ALL) is a malignant disease characterized by an uncontrolled proliferation of immature lymphoid cells.[1] It is the most common pediatric malignancy and accounting for 20%-30% of adult acute leukemia. Recently, a distinct patient group named adolescents and young adults (AYAs; ages 15~39 years) as defined by the National Cancer Institute (NCI), has received increasing attention in ALL patients.[2] AYAs diagnosed with ALL differ considerably from younger children or older adults, who usually face unique challenges throughout their disease trajectory including unfavourable biological characteristics, psycho-social problems and survival disadvantages.[3 4] It is reported that AYAs compared with pediatric usually experienced worse outcomes with event-free survival ranging from 57 to 71%, this survival disparity is likely due to differences in anti-tumor regimens and treatment-related toxicities.[5] Use of intensive pediatric-inspired regimens in AYA populations has demonstrated significant improvements in overall survival (OS).[6] The backbone of pediatric-inspired regimens includes asparaginase and corticosteroids, both of which are associated with more toxicity and poor tolerance. Actually, AYAs presented a greater risk of treatment-related mortality (TRM) than younger patients.[7] However, few study focused on exploring the influencing factors of treatment-related mortality (TRM) in AYAs.
With increasing clinical experience, the management and prevention of infectious complications have emerged as key challenges in ALL. It is worth noting that the intensified and prolonged use of chemotherapeutic drugs is usually associated with an increased risk of infections. Notably, bloodstream infections (BSIs) are still the cardinal infections throughout the course of chemotherapy in leukemic patients and may lead to fatality, even if antibacterial/anti-fungal prophylactic regimens have been administered.[8] A multi-center study performed in China showed that the treatment-related mortality rate of ALL patients was 2.9%, while infection accounted for 73.4% of the causes of death, and BSIs accounted for 58.8%.[9] In recent years, significant efforts have been made to discovering the pathogen distributions and management of infectious complications in pediatrician and adult ALL patients.[10 11] However, few analyses of the epidemiology, resistance patterns of bacterial pathogens, and prognostic factors are available for AYAs diagnosed with ALL. In addition, the potential BSI-related risks factors in the AYAs population are still pending, and the whole process management of BSIs of this population inclining to which one remains unclear. Thus, recognizing and understanding those characteristics of AYA patients has essential clinical implications for effective cancer management, patient functioning, and cancer survivor-ship.
Here, we reported the BSI-related event profiles according to age cohort for ALL patients, explore the epidemiology, resistance patterns of bacterial pathogens, and prognostic factors of BSIs, and further compared the similarities and differences between AYAs patients and other age groups.