The RRM1 3′-UTR SNP rs1042919 and promoter SNP rs1561876 are reported to be associated with decreased intracellular ara-CTP levels during Ara-C therapy, and increased risk of relapse and/or worse event free survival (EFS) in Caucasian AML patients treated with cytarabine and cladribine [18]. This evidence concerns the gene RRM1 and acute myeloid leukemia.