Prolonged effect of alpha Interferon after discontinuance of treatment in chronic myelogenous leukemia patients.

14 patients out of a group of 73 affected by CML and treated with alpha-2-IFN, who had obtained hematological and cytogenetic response, were selected to be submitted to autologous BMT. In all patients the IFN treatment was interrupted to obtain an increase of the peripheral WBC necessary for its collection by means of leukapheresis. After a median time of 20.5 weeks from discontinuance of therapy, most patients are still under hematological disease control. Serially performed cell cultures have shown deeply and persistently reduced growth patterns; cytogenetic analyses have displayed Ph' mosaicism, but with a progressive increase in time of Ph' + cells. Such findings reveal that the effect of alpha-2-IFN in CML patients can be unexpectedly prolonged after discontinuance of treatment. A possible explanation might be found in the complexity of the biological mechanisms of action of IFN, thus giving this drug promising therapeutic prospects in the treatment of CML.