Delayed cytogenetic response with prolonged interferon-alpha treatment in chronic myeloid leukemia patients: quantification of BCR-ABL transcript by competitive reverse transcription-polymerase chain reaction

Interferon-alpha (IFN) induces a major reduction of the Philadelphia chromo some (Ph) positive clone in about 40% of patients with chronic myelogenous leukemia (CML) in chronic phase (CP) and in a substantial minority a comple te cytogenetic response (CCyR), predicting a favorable outcome.(1,2) Most o f the major CyR are obtained within one year from starting therapy; we pres ent data concerning patients in whom late major and complete CyR were achie ved after prolonged treatment with IFN.