Prognostic Impact of p190 and p210 Co-Expression in Early Molecular Response in Chronic Myeloid Leukemia (CML) Patients Treated with Tyrosin Kinase Inibitors

Background: Expression of p190 BCR-ABL mRNA is generally considered to be confined to patients with acute lymphoid or more rarely myeloid leukemias, whereas p210 BCR-ABL mRNA is the hallmark of CML. In reality it is not uncommon the presence of p190 m-RNA in p210 CML in chronic phase, due to alternative or missplicing. Its presence seems to have no impact on prognosis in the pre-TKI era, although it may be expression of genomic instability.

Aim: Primary object of this study was to investigate if the co-expression might influence the rate of early outcome surrogate endpoints such as such as optimal molecular response (EMR; BCR-ABL < 10% (IS) at 3 month and BCR-ABL < 1% or 6 month). in patients treated with TKI.

Methods: Were evaluated patients with CML in chronic phase treated with TKI at our institution. We excluded cases with less than one year of treatment or treated with conventional chemotherapy. The fusion transcripts BCR-ABL were evaluated at diagnosis in peripheral blood by NESTED-PCR and the molecular response were evaluated in peripheral blood with Real-Time PCR. The patients were divided into two groups, "double transcripts" (DT) and "single transcript" (ST).

Results: A total of 34 patients were analyzed. The median age was 61 years (range 22-80) and 26 (68%) were male. Ten patients (29%) were DT and twenty-fouru(71%) ST. The distribution according to Sokal score was: 2 (10%), 5 (50%) 3(30%) patients for low, intermediate and high risk in the DT, whereas 13 (54%), 10 (41%) 1 (5%) low, intermediate and high risk in ST, respectively. The optimal response at 3 month was achieved in 3 patients with DT and 20 patients with ST ( 10% vs 83), at 6-month optimal response was achieved in 3 patients with DT and 20 patients with ST (10% vs 83). No patients with BCR-ABL > 10 % at 3 months, achieved molecular response at 6 months.

Summary/Conclusion: In our study the co-expression of p190 and p210 BCR-ABL transcripts influences the early molecular response to TKI and suggesting the need for a larger validation study