HSCT from an HLA matched donor (MD) only was indicated for patients with (1) PCR-MRD load of ≥10−3 and <10−2 at EOC or (2) low hypodiploid or KMT2A-AFF1 positive ALL and an MRD load of <10−3 not negative on TP2 [PCR-MRD, medium risk (MR)]. This evidence concerns the gene AFF1 and acute lymphoblastic leukemia.