Significance of ELN Provisional Response Definitions In Predicting Long-Term Outcomes of Patients with CP-CML Treated with Dasatinib After Imatinib Failure.
Authors: Cortes Jorge E. , Shah Neil P. , Schiffer Charles A. , LeCoutre Philipp D. , Saglio Giuseppe , Quintás-Cardama Alfonso , Kantarjian Hagop , Jabbour Elias , Bahceci Erkut , Chen Allen , Lambert Alexandre , Guilhot Francois 
Published: October 2019

Abstract
Abstract 3439

Introduction:
The European LeukemiaNet (ELN) recommendations for the management of chronic phase chronic myeloid leukemia (CP-CML) have provisionally defined criteria for suboptimal and failure to second-generation tyrosine kinase inhibitors (TKIs) (Baccarani et al., J Clin Oncol. 27 (35):6041-51, 2009). We tested the significance of these definitions in 3 studies of dasatinib after imatinib failure.

Methods:
Data from 1150 treated patients (pts) included in the 3 studies [CA180-013 (n=387); dasatinib only arm of CA180-017 (n=101); CA180-034 (n=662)] were analyzed. For the purpose of this analysis, we modified the 2009 ELN recommendations to add an optimal response category as shown in Table 1.

Background:
The median age of the pts included in this analysis was 56 yrs (range, 18–85) and the median duration of CML in these pts was 58 months (range, 0.9–250.8). Thirty-eight percent of the pts had received imatinib at a dose > 600mg/day and 45% had been on imatinib therapy >3 yrs. Twenty-four percent of pts included in this analysis had demonstrated imatinib-intolerance. Thirty-five percent of pts had mutations before the start of dasatinib therapy (5% had T315l).

Results:
Rates of optimal response at 3, 6 and 12 months were 51%, 44% and 36%. Rates of suboptimal response at 3, 6 and 12 months were 7%, 16% and 27%. Rates of failure response at 3, 6 and 12 months were 29%, 34% and 37%. Rates of warning response at 3 and 6 months were 12% and 6%. The starting dose of dasatinib did not influence these response rates. The group defined as suboptimal at 12 months (of whom 52% had already achieved CCyR) had a higher probability of achieving CCyR within 2 yr (83%) compared to the groups defined as suboptimal at 6 months (69%) or 3 months (51%). This suboptimal group at 12 months also had a higher 2 yr progression-free survival (PFS) (92%) compared to the suboptimal groups at 6 months (82%) and 3 months (80%). The probability of achieving an MMR within 2 yr was slightly higher in pts defined as optimal at 6 months (80%) vs. those at 3 months (71%). However, the probability of achieving an MMR within 2 yr showed minimal change for the suboptimal (31-35%) or the failure (5%) response groups defined at 3, 6 and 12 months. The pts with a warnings response had a profile that was intermediate between suboptimal and failure response. Table 2 summarizes 2 yr outcomes based on response.

Conclusions:
These results suggest that the 2009 ELN provisional response definitions may be helpful in predicting long term outcomes in pts receiving second-line dasatinib therapy. In this cohort of pts, optimal responders identified themselves rapidly as did pts with failure. However, the outcome of pts defined as suboptimal at 12 months appeared more favorable than that of pts defined as suboptimal at 3 and 6 months. This, in addition to the higher proportion of pts classified as suboptimal at 12 months, compared to those classified as suboptimal at 3 and 6 months, may suggest that the ELN defined cut-off between optimal vs. suboptimal at 12 months (i.e. MMR) may need to be modified in order to make the prognosis for suboptimal response more consistent across different time points. Pts classified in the warnings category at 3 and 6 months had an outcome intermediate between those with suboptimal and failure response.

Disclosures:
Cortes: Bristol-Myers Squibb: Research Funding; Novartis: Research Funding; Pfizer: Research Funding. Shah:Bristol-Myers Squibb: Consultancy; Novartis: Consultancy; Ariad: Consultancy. LeCoutre:Novartis: Honoraria, Research Funding; Bristol-Myers Squibb: Honoraria. Kantarjian:Novartis Pharmaceuticals: Research Funding; Bristol Myers Squibb: Research Funding. Jabbour:GlaxoSmithKline: Research Funding. Bahceci:Bristol-Myers Squibb: Employment. Chen:Bristol-Myers Squibb: Employment. Lambert:Bristol-Myers Squibb: Employment. Guilhot:Bristol-Myers Squibb: Consultancy; Novartis: Consultancy.