Evolving modalities of treatment with interferon alfa-2b for Ph1-positive chronic myelogenous leukaemia

We have administered interferon alfa-2b, alone or in combination with chemotherapy, to 126 Ph1-positive chronic myelogenous leukaemia patients. Of 71 early chronic phase (CP) patients (less than 12 months from diagnosis), 41 (58%) obtained a complete haematological response (CHR). Daily interferon was more effective than intermittent administration. In previously untreated patients, the response was significantly influenced by risk status at diagnosis. Thirty-four out of 71 (48%) patients improved cytogenetically, the median of Ph1+ mitoses declining from 100% to 66% with complete Ph1-suppression in one case. Of 46 late CP patients (greater than 12 months from diagnosis), 32 (70%) achieved CHR with interferon alone or combined with chemotherapy. All 10 patients with disease well controlled by chemotherapy obtained stable CHR with interferon alone. Of 36 partial responders to conventional chemotherapy, 22 (61%) obtained CHR on interferon plus low-dose hydroxyurea. Ph1 mosaicism was reached by 16 (35%) late CP patients (median Ph1+ cells 75%). Of nine accelerated phase patients on interferon plus chemotherapy, one attained CHR, and two responded partially. At a median follow up of 36 months, of 41 CHR patients in early CP, 15 are controlled on interferon, 12 have had autologous bone marrow transplantation (BMT), and two allogeneic BMT. Blastic transformation (BT) has occurred in eight of 41 CHR patients (19%) versus 17 of 30 (57%) non-responders and partial responders to interferon. At a median follow up of 22 months, of 32 late CP patients obtaining CHR, 26 remain on interferon, one had allogeneic BMT, one had autologous BMT, and one developed BT (versus five out of 14 with less than CHR). These studies confirm the haematological and cytogenetic efficacy of interferon in CML and indicate that the disease status at the start of treatment is critical in determining the success of therapy.