Blast phase characteristics differ in TKI-, non-TKI–treated CML patients

By Shreeya Nanda, Senior medwireNews Reporter

Features of the blast phase, such as blast cell morphology and accompanying cytogenetic changes, vary between chronic myeloid leukaemia (CML) patients who received tyrosine kinase inhibitor (TKI) therapy and those treated in the pre-TKI era, research shows.

Between 1991 and 2011, 23 CML patients treated with TKIs progressed to blast phase. Of these 56.5% had a “usual” myeloblastic or lymphoblastic blast type and the remaining 43.5% had an “unusual” blast type, either monoblastic, megakaryoblastic, basophilic, eosinophilic or biphenotypic.

Of the 44 patients who received non-TKI therapy, such as interferon, and who developed blast phase, 88.6% and 11.4% had usual and unusual blast types, respectively.

Additionally, TKI-treated patients had a significantly higher peripheral white blood cell (WBC) count and lower bone marrow blast percentage at blast phase than those in the pre-TKI era. Other factors, such as haemoglobin concentration, platelet count, mean corpuscular volume and bone marrow fibrosis, did not vary significantly between the two groups.

WBC count was significantly higher in TKI-treated patients with an unusual blast type compared with unusual blast type patients in the non-TKI group. WBC count tended to be higher and bone marrow blast percentage lower in the TKI-treated patients with a usual blast type than their non-TKI-treated counterparts, but the differences were not statistically significant.

Analysis of available cytogenetic data showed that 17 of 23 patients who progressed to blast phase had aberrant chromosomal changes over and above the presence of the Philadelphia chromosome, with no significant difference in the likelihood of such changes between those who were and were not given TKIs.

Anand Lagoo (Duke University Medical Center, Durham, North Carolina, USA) and co-workers note that most of these cytogenetic aberrations were present months before the onset of blast phase.

They write in the American Journal of Clinical Pathology that based on their findings “it is not surprising that the blast phase prognosis for TKI-treated patients is only marginally better than for patients in the pre-TKI era.”

The researchers conclude: “Large-scale studies using advanced techniques such as next-generation sequencing are needed to improve prediction, early detection, and management of CML blast phase.”

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