(A) Response rates of initial therapy of LCH compared with childhood ALL and AML. (B) Overall 5-year survival percentages. RO+ is defined as patients with LCH that involves risk organs, whereas RO– defines patients with multisystem disease without risk organ involvement (ie, liver, spleen, hematopoietic system, and lung). NAD, no active disease; Active Disease I/B, active disease is still present but has shown an intermediate response (unchanged disease or regression but with evidence of some new involvement) or is improved (ie, B for better); PD, progressive disease. Response rates to induction therapy and OS rates for ALL and AML for the time period of the LCH III trial were extracted from Pui et al.⁶