Introducing a prognostic score for successful treatment-free remission in chronic myeloid leukaemia.

The modern management of chronic myeloid leukaemia (CML) identifies a new therapeutic goal of treatment-free remission (TFR). Half of CML patients in durable deep molecular response (DMR) (MR4 or better) can remain off tyrosine kinase inhibitors (TKIs) without experiencing loss of major molecular response. Despite a large number of TFR studies to date, there are no consistent predictors of successful TFR. We conducted a single-centre cohort study on 197 patients discontinuing TKIs in DMR ≥1 year and TKI therapy ≥3 years. After TKI discontinuation, 98 patients (49.7%) lost MR4; of these, 90 (91.8%; and 45.7% of the whole cohort) lost major molecular response (MMR or MR3) after a median of 3.8 months (1-93.3). The 2-year probability of TFR (pTFR) was 57.7%. In multivariable analysis, male sex, age at diagnosis >40 years, faster achievement of MR4 and longer duration of DMR were the only variables significantly associated with higher pTFR. Based on the multivariable analysis results, we built a TFR prognostic score (TPS) able to distinguish three groups with different 2-year pTFR: good (89.9%), intermediate (61.2%) and poor (18.4%) TFR probability (p < 0.0001). We validated the TPS on an independent cohort of 91 patients. We propose that the TPS could become a useful guide for CML clinicians.