Serial changes in bone marrow cellularity, reticulin fibrosis and microvessel density in patients with chronic myeloid leukemia (CML) in chronic phase treated with imatinib

Abstract

6596 Background: Imatinib Mesylate, a BCR-ABL tyrosine kinase inhibitor produces sustained complete hematological response (CHR) in CML patients in chronic phase. There is a paucity of information on the effects of imatinib on the bone marrow (BM) morphology and angiogenesis. We evaluated the sequential changes in these parameters in 22 CML chronic phase patients treated with first line imatinib (400 mg) and compared with 10 controls (non-hematological malignancies). Methods: Trephine BM biopsies were evaluated by means of morphology, morphometry, Gomori’s stain and CD 34 staining. Reticulin fibrosis was graded from grade 1 to grade 4. Microvessel density (MVD) was calculated by counting the microvessels in hot spots (400 ×). Final value was mean of 10 fields. Total vascular area (TVA) was calculated by image analysis and expressed as percentage of the total area. Results: 22 patients were included in the study. Median age was 34 years (range 20–58 years). All patients attained a CHR at a median of 18 days. Major cytogenetic response was seen in 64%, minor response in 27% and no response in 9% of patients. Baseline BM cellularity was increased in all patents as compared to controls. The median cellularity at 6 months and 1 year was decreased to 60% and 50% respectively. The median grade of reticulin fibrosis at baseline was grade 3 as compared to controls (median grade 1). There was a significant decrease in reticulin fibrosis at 6 months and 1 year (median-grade 1, p=0.04). The median MVD at baseline was 8.25 (range 6–26) and was increased as compared to controls (median MVD-3.6). There was a significant decrease in MVD at 6 months and 1 year (median MVD-4.0, p=0.04). Similarly the TVA decreased from 6.2% at baseline to 4.3% at 1 year. These changes correlated with the cytogenetic responses. Two patients who had disease progression during therapy showed reversal in the bone marrow changes. Conclusions: Imatinib Mesylate produces significant effects on bone marrow morphometry and angiogenesis in patients with CML in chronic phase. There is a consistent decrease in bone marrow cellularity, reticulin fibrosis and microvessel density during therapy. No significant financial relationships to disclose.

Effect of Imatinib on Bone Marrow Morphology and Angiogenesis in Chronic Myeloid Leukemia

“…This suggests an antiangiogenic role of imatinib. Lokeshwar NM et al [26] also observed significant reduction in MVD in CML patients after imatinib therapy (Table 7). Kvasnicka HM et al observed that decrease in microvascularization after imatinib therapy is associated with the reversal of myelofibrosis [27].…”