Cumulative incidence of osteonecrosis in patients of the BFM group. Data are shown (A) in age groups (1 to <6, 6 to <10, 10 to <15, 15 to <18 years) and (B) in age groups (1 to <10, 10 to <18 years) and randomization arm as treated. 5 y-CIO, 5-year cumulative incidence of osteonecrosis; DXM, dexamethasone; ON, number of osteonecrosis; PDN, prednisone; SE, standard error.