Comment on low‐dose tyrosine kinase inhibitors before treatment discontinuation do not impair treatment‐free remission in chronic myeloid leukemia patients: Results of a retrospective study

We read with interest the study by Cayssials et al1 describing how in chronic myeloid leukemia, a reduced dosage of tyrosine kinase inhibitors (TKIs) does not seem to reduce the possibility of a prolonged treatment-free remission in comparison with the standard TKI dosage. We observed that the reduction of TKI therapy was in most cases related to nonhematological toxicity, with dose reductions being due to hematological toxicity in only 2 cases; we should point out that generally hematological toxicities are more frequent among patients with advanced disease. The appearance of toxicity during TKI treatment is related to patient-specific features that influence pharmacodynamics; as such, plasma drug monitoring could be a correct approach to maximizing the efficacy of therapy and minimizing adverse events.2, 3 We are aware that plasma drug monitoring is not a diffused and standardized technology, but we feel that knowing whether patients experiencing toxicity have higher plasma concentrations could be valuable, especially with respect to the assessment of responses and the possibility of discontinuing TKIs in such patients. Some previous studies4-6 have reported a nondetrimental effect of de-escalation of TKI therapy before treatment discontinuation in patients with a deep molecular response, but they have not been able to explain this phenomenon. We agree with the authors that patients treated with TKIs at a low dose on account of treatment-related toxicity could achieve the same treatment-free remission as patients treated with the standard dosage, but in our opinion, the plasma drug dosage could be helpful for understanding this phenomenon and designing tailored therapy. No specific funding was disclosed. The authors made no disclosures.