Asian population may have a lower incidence of hip osteonecrosis in childhood acute lymphoblastic leukemia.

Osteonecrosis (ON), a long-term complication of acute lymphoblastic leukemia (ALL) treatment affects patients' quality of life. Although the incidence of any ON, including asymptomatic, was 21.7% among children with ALL in the U.S., the actual incidence and risk factors in Asia remain unknown. For over 11 years, we performed hip magnetic resonance imaging (MRI) screening to detect asymptomatic ON while initiating maintenance chemotherapy in newly diagnosed children with ALL. Overall, 164 of 175 patients underwent hip MRI screening. The incidence of symptomatic or any ON was 3.0% and 11.6%, respectively. Asymptomatic ON in patients < 10 and ≥ 10 years old was 4.0% and 35.9%, respectively (P < 0.001). In multivariate analysis, age ≥ 10 years was the only significant risk factor. Asymptomatic ON with necrosis of > 30% of the epiphyseal surface of the femoral head was detected in four patients (2.4%). All were ≥ 10 years. Three of them progressed to severe symptomatic ON. The incidence of any ON in Asia may be lower than that seen in the only screening study in the U.S. Future studies should clarify factors affecting such regional differences and develop an effective approach to avoid the progression of ON in children with ALL.