Recombinant
interferon-α represents a well-established therapeutic option for the treatment of
polycythemia vera and
essential thrombocythemia. Recent studies also suggest a role for recombinant
interferon-α in the treatment of 'early stage'
primary myelofibrosis, but few studies have reported the bone marrow changes after clinically successful
interferon therapy. The aim of the present study is to detail the histological responses to recombinant
interferon-α in
primary myelofibrosis and post-
polycythemia vera/post-
essential thrombocythemia myelofibrosis and to correlate these with clinical findings. We retrospectively studied 12 patients with
primary myelofibrosis or post-
polycythemia vera/post-
essential thrombocythemia myelofibrosis, who had been treated with recombinant
interferon-α. Six patients had received other prior cytoreductive
therapies. Bone marrow biopsy was assessed for the following histological parameters: (i) cellularity; (ii) myeloid-to-erythroid ratio; (iii) megakaryocyte tight clusters; (iv) megakaryocyte and naked nuclei density; (v) megakaryocytic atypia; (vi)
fibrosis; and (vii) the percentage of blasts. Clinical and laboratory data were included: (i) constitutional symptoms; (ii)
splenomegaly, if present; and (iii) complete cell blood count. The clinical response to
therapy was evaluated using the International Working Group for
Myelofibrosis Research and Treatment/European LeukemiaNet response criteria. The Dynamic International Prognostic Scoring System (DIPSS) score was calculated before and after recombinant
interferon-α administration. Successful
interferon therapy for
myelofibrosis was associated with a significant reduction of marrow
fibrosis, cellularity, megakaryocyte density and naked nuclei density. The presence of JAK2(V617F) mutation correlated with improved DIPSS score. JAK2(V617F)-negative cases showed worsening of such score or evolution to
acute myeloid leukemia. Cytogenetic analysis documented a normal karyotype in all cases. In conclusion, successful clinical response to
interferon-α correlates well with an improvement of bone marrow morphology. The prognostic effect of such
therapy may be influenced by the JAK2 mutational status. Additional studies are needed to confirm these preliminary data.