Prognostic Discrimination of Children and Adolescents with Chronic Myeloid Leukemia Based on the EUTOS Long Term Survival (ELTS) Score
Authors: Millot Frédéric , Guilhot Joelle , Suttorp Meinolf , Meral Güneş Adalet , Sedlacek Petr , De Bont Evelina S , Li Chi Kong , Kalwak Krzysztof , Lausen Birgitte , Culic Srdjana , De Moerloose Barbara , Biondi Andrea , Baruchel Andre 
Published: November 2019

Abstract

The Sokal score for patients less than 45 years can be used for the prognostic discrimination in the pediatric population. Limited data are available regarding the utility of the EUTOS score in the pediatric population (Gurrea Salas et al, Ann Hematol 2015). Recently, a new EUTOS score, the EUTOS Long Term Survival (ELTS) score was validated in the adult population (Pfirrmann et al, Leukemia 2016). The international registry for chronic myeloid leukemia (CML) in children and adolescents (I-CML- Ped Study registered at www.clinicaltrials.gov as NCT01281735) gave us the opportunity to test this score in this population.
Aim: The aim of this analysis was the comparison of risk groups allocations and outcome between the Sokal (<45 years) score and the ELTS score in the pediatric population.
Patients and Methods: As of June 1, 2016, 462 children and adolescents less than 18 years old were enrolled in the I-CML-Ped study between January 2011 and April 2016. Among them, 350 patients diagnosed with CML in chronic phase according to the ELN definition and treated with imatinib (+/- hydroxyurea or anagrelide) as first line treatment were eligible for analysis. For progression free survival (PFS) analyses, events of interest included progression to accelerated phase or blast crisis and deaths irrespective of its cause, whichever came first. For survival analyses, the event of interest was death from CML, deaths from other causes being considered as competing events, as initially designed in the ELTS score model. Estimates were compared by the log-rank test and Gray test respectively. Level of significance was 0.05.
Results: The median follow up of the 350 patients was 3 years (range 1 month to 6 years). Progression and/or death (whichever came first) occurred in 23 patients. For the entire cohort of patients the 5-year PFS was 92% (95% CI: 88%-94%) and the 5-year survival accounting for CML death was 97% (95% CI: 94%-99%). Of the 308 patients allocated to low (n=54), intermediate (n=118) and high (n=136) risk groups by the Sokal (<45 years) score, events (progression and/or deaths) occurred in 5.5%, 5% and 9.5%, respectively. Estimation of the 5-year progression free survival accounting for CML death according to these 3 risk groups was 93% (95% CI:81%-98%), 94% (95% CI: 87%-97%) and 88% (95% CI: 80%-93%), respectively (p = 0.376, overall). Estimation of the 5- year survival accounting for CML death according to these 3 risk groups was 100%, 97% (95% CI: 92%-100%) and 96% (95% CI: 89%-100%), respectively, (p = 0.576, overall). Of the 308 patients allocated to low (n=199), intermediate (n=68) and high (n=41) risk groups by the ELTS score, events (progression and/or deaths) occurred in 6%, 8.8% and 24%, respectively. Differences in PFS according to these risk groups were highly significant (p < 0.0001, overall) (Figure 1). Estimation of the 5-year PFS according to these 3 risk groups was 96% (95% CI:92%-98%), 94% (95% CI: 76%-95%) and 67% (95% CI: 49%-82%), respectively. Estimation of the 5-year survival related with CML death according to these 3 risk groups was 99% (95% CI:95%-100%), 96% (95% CI: 88%-99%) and 89% (95% CI: 10%-98%), respectively (p = 0.107, overall).
Conclusion: ELTS score showed better differentiation regarding progression free survival than Sokal (<45 years) score in children and adolescents with CML. However , ELTS score has failed to predict the survival accounting for CML death only. A specific prognostic score incorporating clinical, biological and molecular features is still needed for the pediatric population.
Figure 1. Figure 1.

Disclosures
Suttorp: Novartis, Bristol Meyer Squib, Pfizer: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding. Biondi:BMS: Membership on an entity's Board of Directors or advisory committees; Novartis: Membership on an entity's Board of Directors or advisory committees, Other: Advisory Board; Cellgene: Other: Advisory Board.