ABL1 and chronic myelogenous leukemia, BCR-ABL1 positive: In younger patients, TFR may be pursued more aggressively by some CML experts and patients, with changes in therapy in the absence of a DMR (BCR::ABL1 transcripts on International Scale [IS] ≤ 0.01%) after 3–5 + years of frontline TKI therapy (discussed later).