Imatinib as Front-Line Treatment in Chronic Myelogenous Leukemia: How Important is the Achievement of Complete Cytogenetic Response after 3 Months?

Abstract 4271

The achievement of Complete Cytogenetic Response (CCyR) (Ph+ cells 0%) with Imatinib treatment still remains the most important objective in Chronic Myelogenous Leukemia (CML) patients. According to The European Leukemia NET guidelines, CCyR should be achieved within the 12^th month of treatment while at 3 months of treatment the goal should be complete haematological response. To address the prognostic role of the early achievement of CCyR, we revised 108 chronic phase CML patients [M/F 57/51, median age 54.9 years, interquartile range (IR) 40.8 – 68.1] treated with front-line Imatinib at our Institution from June 2002 to June 2008 who had evaluable karyotype after 3 months of treatment. At onset, median WBC and PLT counts were 78.4 × 10⁹/l (IR 34.0 – 135.9) and 399 × 10⁹/l (IR 282 – 585), respectively. Sokal risk score was low in 52 patients (48.1%), intermediate in 49 (45.4%) and high in 7 (6.5%); a short pre-treatment phase (< 3 months) with Hydroxyurea was administered to 94/108 patients (87%). After 3 months of Imatinib treatment, 84 patients (77.7%) achieved CCyR while 24 patients (22.3%) still presented Ph+ metaphases (median value 40%, IR 20 - 80) at cytogenetic analysis. At univariate analysis, factors with a negative prognostic impact on achievement of CCyR at 3 months were palpable spleen enlargement (p=0.002), WBC count at onset > 100.0 × 10⁹/l (p=0.01) and pre-treatment with Hydroxyurea (p=0.032); on the contrary, sex, age, Sokal risk score and PLT value did not appear to affect early CCyR achievement. Among the 84 patients in CCyR after 3 months, there were 10 failures during follow-up (6 cytogenetic relapses, 2 molecular relapses and 2 evolution to blastic phase); among the 24 patients who did not achieve early CCyR, there were 12 failures during follow-up (9 primary resistances and 3 cytogenetic relapses). The difference in the incidence of failures during follow-up in the 2 groups was highly significant (p<0.001). In conclusion, the achievement of CCyR at 3 months seems unrelated to traditional prognostic factors (Sokal); furthermore, in our experience it appears to have an important prognostic role, as patients not achieving it showed a significantly higher rate of failures during the follow-up.