Abstract
The European Treatment and Outcome Study (EUTOS) long-term survival (ELTS) score predicts disease-specific death in patients with chronic myeloid leukemia (CML) being treated with imatinib during the chronic phase (CP) of the disease. However, it is unclear whether the ELTS score predicts CML-related events or treatment responses. This study evaluated the predictive value of the ELTS score regarding prognosis and treatment response in patients with CML-CP. Clinical data were retrospectively obtained from patients enrolled in the CML Cooperative Study Group (CML-CSG), which included patients diagnosed with CML-CP from April 2001 to January 2016, and treated with any tyrosine kinase inhibitor (TKI) as first-line therapy. Among 342 eligible patients, the ELTS scores indicated low-, intermediate-, and high-risk in 74%, 21%, and 5% of patients, respectively. Patients with high ELTS scores had significantly higher disease-specific mortality and worse event-free survival, progression-free survival, and overall survival. Among four risk scores, including the Sokal, Hasford, EUTOS, and ELTS scores, risk stratification by the ELTS score had the highest predictive value in assessing patient prognosis, and also in treatment responses. In fact, the EUTOS and ELTS scores were able to predict the major molecular response within 12 months. Most importantly, the ELTS score was the only scoring system that predicted deep molecular response at any time, regardless of risk level (65.0%, 43.7%, and 23.5% in low-, intermediate-, and high-risk groups, respectively). Compared to other risk scores, the ELTS score was the most sensitive risk classification tool for the four endpoints of interest in this study, as well as molecular responses in patients with CML-CP.