For treatment of BCR–ABL-positive acute lymphoblastic leukaemia or lymphatic blast crisis of CML, TBI-containing regimens are generally preferred due to the higher irradiation sensitivity of lymphoid blasts and due to the risk of relapse in the central nervous system (Granados et al, 2000). The gene discussed is BCR; the disease is chronic myelogenous leukemia, BCR-ABL1 positive.