Multivariable Cox regression analyses of OS and RFS. Multivariable analyses of OS and RFS were performed for covariates of age, sex, disease burden, and HLH-LT status in a model including all patients that met criteria for HLH-LTs (A) and with HLH-LT group separated into peak ferritin groups (10-100 000 ng/mL and ≥100 000ng/mL) (B). HRs with 95% CIs are shown. High disease burden was defined as BM disease burden ≥5%, the presence of extramedullary disease, or evidence of leukemia in the peripheral blood. No/low disease burden was defined as BM disease burden <5% and the absence of extramedullary disease or peripheral lymphoblasts. P values: 2-tailed significance level was set at .05.