KMT2A and leukemia: Topoisomerase II inhibitor exposure is most frequently associated with early‐occurring (median 2–3 years from exposure) subsequent leukemias that characteristically harbor MLL gene rearrangements,11 whereas alkylating agent associated leukemias are observed later (median 4–7 years from exposure) and are most typically associated with genetic alterations involving chromosomes 5 and 7.12, 13, 14