Possible correlation between fusion pattern of BCR/ABL mRNA and clinical response to α-interferon in chronic myelogenous leukemia

Twenty six patients with Philadelphia chromosome (Ph₁) positive chronic myelogenous leukemia (CML) treated with IFN-α were classified on the basis of the fusion pattern of BCR/ABL chimeric mRNA determined by a reverse-transcriptase-polymerase chain reaction (RT-PCR) method. The relationship between the fusion pattern of BCR/ABL mRNA and the clinical outcome was also analysed. Twelve patients showed M-bcr exon 3/ABL exon 2 (B3/A2) chimeric mRNA and nine had M-bcr exon 2/ABL exon 2 (B2/A2) mRNA. Eleven of the 12 patients with B3/A2 achieved complete hematological response with IFN-α therapy, as did three of the nine patients with B2/A2. The mean duration to blastic crisis was significantly longer in the B3/A2 patients (mean 52.4 months) than in the B2/A2 patients (mean 26.2 months) (p<0.01). These results suggest that the fusion pattern of BCR/ABL mRNA may affect the therapeutic response to IFN-α and clinical outcome in CML patients.