Infectious Complications in Philadelphia-Negative Adolescent and Young Adult Acute Lymphoblastic Leukemia Patients in the Era of Pediatric-Inspired Regimen

Introduction Pediatric acute lymphoblastic leukemia (ALL) has cure rates exceeding 90%, while adult ALL has a 3-year survival rate of only 40–50%. Adolescents and young adults (AYAs) face unique challenges due to age-related factors and high-risk disease features. Although pediatric-inspired regimens improve survival, intensive chemotherapy increases susceptibility to severe infections. Methods A retrospective analysis was conducted on AYA-ALL patients treated at Chiang Mai University Hospital from 1 January 2007 to 31 December 2023. Patients were classified into pediatric-inspired (TPOG) or adult regimens (Hyper-CVAD or GMALL). Infections were categorized as clinically documented infections (CDI) or microbiologically documented infections (MDI). Multivariate logistic regression was used to identify infection risk factors. Results Among 94 patients (62.8% male; median age 22.9 years), 56.4% received TPOG and 43.6% received adult regimens. Infectious complications occurred in 79.8% of patients, with higher rates in the adult regimen group (90.2% vs. 71.7%, p = 0.03). CDI was more frequent in the adult group (73.4% vs. 52.8%, p = 0.04), while fungal infections were more common in the TPOG group (26.4% vs. 9.8%, p = 0.04). Adult regimens significantly increased infection risk (OR 3.55; 95% CI 1.02–12.36, p = 0.04). Infection rates peaked during induction (47.8%) and consolidation (51.8%). During induction, MDI was lower in the adult group (21% vs. 79%, p = 0.01), while CDI was higher during consolidation (69% vs. 30%, p < 0.01). Gram-negative bacteria were the most common pathogens (85%), particularly E. coli (27%) and Salmonella spp. (21%). Fungal infections affected 19.1% of patients, with invasive pulmonary aspergillosis being the most common (11.7%). Conclusion AYA-ALL patients are highly susceptible to infections, especially those receiving adult regimens. Fungal infections were notably more common in patients on the TPOG regimen. Strengthening infection prevention and providing early treatment are vital for improving patient outcomes.