EFS of children with My⁺ and My⁻ BL ALL according to NCI risk classification. (Top) Standard risk: 138 My⁺ BL (hatched line) and 657 My⁻ BL (solid line) patients were followed for 6 years. (Bottom) Poor risk: 79 My⁺ BL (hatched line) and 456 My⁻ BL (solid line) were followed for 5 years. Percentages of patients achieving EFS during follow-up were calculated as described in Materials and Methods. The number of patients in each group remaining in follow-up at the indicated time points is shown in the inset.