Combination of EUTOS score and 3-month BCR-ABL transcript level identifies a group of good-risk chronic myeloid leukemia patients with favorable response to frontline imatinib therapy

EUTOS score at diagnosis and early molecular response (EMR), defined as BCR-ABL transcript 10% after 3 months of therapy, separately proved able to predict long-term outcomes in Chronic Myeloid Leukemia (CML) patients treated with Tyrosine Kinase Inhibitors (TKI). In our study, 74% of all patients attained EMR. We found a strong association between low EUTOS and achievement of EMR, confirming the predictive value of the EUTOS score. Combining the baseline (low EUTOS) and the dynamic response-related parameter (EMR), we identified a “good risk” group of about 70% of CML patients with excellent outcomes on front-line imatinib, both as high probability of a subsequent optimal response (6-month CCyR 84%, 12-month MMR 67%) and favourable survival (5-year EFS 70%, PFS 94% and OS 94%). The few patients (6%) in the “poor risk” group displayed a dismal prognosis, with low chances of CCyR and MMR, almost unavoidable imatinib failure and high rates of progression. Around one quarter of our patients fell in the “intermediate risk” group, comprising a majority of low EUTOS patients failing EMR and few cases with high EUTOS and BCR- ABL 10% at 3 months. Clinical outcomes of this group were closer to the “poor” than to the “good” risk cohort. Patients with high EUTOS could maximally benefit from front-line use of second-generation TKIs, and low EUTOS patients failing optimal 3-month molecular response are candidate for early switch to alternative treatment strategies.