Imatinib mesylate therapy reduces bone marrow fibrosis in patients with chronic myelogenous leukemia

BACKGROUND. Reticulin-stained bone marrow fibrosis is associated with a poor prognosis in patients with chronic myelogenous leukemia (CML). Resolution of fibrosis with therapy may improve patient outcome. METHODS. The effect of imatinib therapy on bone marrow fibrosis was evaluated in 40 patients with chronic-phase CML who were treated after interferon-a failure. RESULTS. Thirty-one patients (78%) had severe (Grade 3 or 4) reticulin fibrosis prior to therapy. After imatinib therapy was administered for 3 to > 24 months, fibrosis was reduced by at least 2 grades in 19 of the 31 patients (61%) and by at least 1 grade in 34 patients (85%). There was no correlation noted between reduction of fibrosis and cytogenetic response. However, a reduction in fibrosis was found to correlate with a reduction in bone marrow megakaryocytosis (P = 0.002). CONCLUSIONS. Treatment with imatinib mesylate appears to reduce CML-associated bone marrow fibrosis in most patients who are treated during the chronic phase of disease. This effect may be independent of the degree of suppression of Philadelphia chromosome-positive cells, and may improve prognosis in patients with CML.