Salvage treatment incorporating arsenic trioxide for pediatric relapsed acute lymphoblastic leukemia: a retrospective real-world analysis

Background Relapsed pediatric acute lymphoblastic leukemia (ALL) confers an unfavorable prognosis. We evaluated the outcomes of an arsenic trioxide (ATO)-incorporating chemotherapy protocol in pediatric first-relapsed ALL. Methods Patients were risk-stratified according to the ALL-REZ BFM 2002 protocol. Group A received an institutional ATO-containing protocol at one university-affiliated hospital between September 2010 and September 2021, while Group B followed the ALL-REZ BFM 2002 protocol at another one in the same city during the similar period. Results Group A comprised 43 patients, 9 high-risk, among whom one (11.1%) underwent allogeneic hematopoietic stem cell transplantation (allo-HSCT). Group B had 35 patients with 15 high-risk among whom 7 (46.7%) received allo-HSCT. In non-high-risk patients, 5-year event-free survival (EFS) was comparable between groups (73.5% vs 70.0%, P = 0.794). Among high-risk patients, EFS was higher in Group A (44.4% vs 13.3%, P = 0.048). Moreover, Group A remained independently associated with better EFS in a multivariable Cox model incorporating allo-HSCT as a time-dependent covariate (HR = 0.50, 95% CI: 0.25-0.99, P = 0.048). Conclusion High-risk relapsed ALL stratified by the ALL-REZ BFM 2002 stratification system carries a poor prognosis. The incorporation of ATO into salvage regimens merits further investigation, and prospective randomized controlled trials would help confirm its promising prognostic advantages.