An extremely delayed cytogenetic response to interferon-alpha in a patient with chronic myeloid leukaemia

In chronic myeloid leukaemia (CML), treatment with interferon alpha IFN-alpha results in loss of the Ph' chromosome in a significant proportion of patients. Most cytogenetic responses occur early at a median of 9 months after initiation of treatment and failure to detect a cytogenetic response within a predetermined period may be a reason for IFN-alpha withdrawal. We report a patient in whom IFN-alpha dosage was initially severely limited by bone marrow suppression but in whom continuing treatment led to a first cytogenetic response only after 53 months. Increasing Ph' negativity over a further 2 years was associated with improving haematological tolerance which permitted IFN-alpha dose escalation and complete cytogenetic remission was achieved at 7 years after diagnosis. This remission has been sustained and has thus followed the most delayed cytogenetic response to IFN-alpha so far reported.