AFF1 and leukemia: After nearly half a year of high-dose methotrexate chemotherapy treatment according to the Chinese Children Cancer Group Infant Acute Lymphoblastic Leukemia 2022 collaborative group protocol (CCCG-iALL-2022) (12, 13) (Supplementary Table S8), the child was successfully given to significantly, alter minimal residual disease (leukemia residue cells) for lower than 10−4 (Supplementary Figure S3; Table S6) and the KMT2A/AFF1 fusion gene for 0 (Supplementary Table S7).