Two different classes of therapy-related and de-novo acute myeloid leukemia?

Two different classes of therapy-related acute myeloid leukemia (t-AML) seem to emerge. One class follows therapy with alkylating agents, increases in frequency with age, often presents with myelodysplasia (MDS), responds poorly to chemotherapy, and shows monosomy 7(-7), monosomy 5(-5), or loss of various parts of the long arms of these chromosomes (5q- and 7q-). The other class is related to therapy with cytostatic drugs targeting at DNA-topoisomerase II, often presents with overt leukemia, responds more favorably to chemotherapy, and shows balanced chromosome aberrations, primarily translocations involving chromosome bands 11q23 and 21q22. These two classes of t-AML may have their counterparts in de-novo acute myeloid leukemia (de-novo AML).