Successful treatment discontinuation in CML patients with full-dose and low-dose TKI: Results from real-world practice

Treatment free remission (TFR) after second-generation tyrosine kinase inhibitors (2G-TKIs) treatment in chronic myeloid leukemia (CML): from feasibility to safety

INTRODUCTION

Chronic myeloid leukemia (CML) prevalence is currently increasing due to the great efficacy of tyrosine kinase inhibitor (TKI) therapy. Discontinuation of treatment in the long-term, owing to avoid off-target side effects or treatment-free remission (TFR), has become an additional treatment goal in CML patients who achieved a deep molecular response (DMR). Second-generation TKIs (2 G-TKIs) have a significantly higher rate of DMR than imatinib. Hence, especially in young patients with a strategy of TFR, 2 G-TKIs are becoming the most frequently used TKIs and may increase TFR attempts in the future.

AREAS COVERED

In this review, the main findings extrapolated from clinical trials and real-life evidence regarding 2 G-TKIs discontinuation were discussed, through broad research on Medline, Embase, and archives from EHA and ASH congresses.

EXPERT OPINION

Overall, TFR rate after 2 G-TKIs is ranging from 40% to 60% for selected patients with sustained DMR and it can be considered a safe procedure, that have become, nowadays, a daily practice. However, many crucial aspects regarding treatment choices, timings, as well as predictive factors, patient communication, and optimal strategies need to be better clarified to improve successful TFR rate.

Twenty years of evolution of CML therapy: how the treatment goal is moving from disease to patient

The introduction of imatinib in 2000 opened the era of tyrosine kinase inhibitors (TKIs) for CML therapy and has revolutionized the life expectancy of CML patients, which is now quite like the one of the healthy aged population. Over the last 20 years, both the TKI therapy itself and the objectives have undergone evolutions highlighted and discussed in this review. The main objective of the CML therapy in the first 10 years after TKI introduction was to abolish the disease progression from the chronic to the blastic phase and guarantee the long-term survival of the great majority of patients. In the second 10 years (from 2010 to the present), the main objective of CML therapy moved from survival, considered achieved as a goal, to treatment-free remission (TFR). Two phenomena emerged: no more than 50-60% of CML patients could be candidates for discontinuation and over 50% of them molecularly relapse. The increased cumulative incidence of specific TKI off-target side effects was such relevant to compel to discontinue or reduce the TKI administration in a significant proportion of patients and to avoid a specific TKI in particular settings of patients. Therefore, the treatment strategy must be adapted to each category of patients. What about the patients who do not get or fail the TFR? Should they be compelled to continue the TKIs at the maximum tolerated dose? Alternative strategies based on the principle of minimal effective dose have been tested with success and they are now re-evaluated with more attention, since they guarantee survival and probably a better quality of life, too. Moving from treating the disease to treating the patient is an important change of paradigm. We can say that we are entering a personalized CML therapy, which considers the patients' age, their comorbidities, tolerability, and specific objectives. In this scenario, the new techniques supporting the monitoring of the patients, such as the digital PCR, must be considered. In the present review, we present in deep this evolution and comment on the future perspectives of CML therapy.

Molecular BCR::ABL1 Quantification and ABL1 Mutation Detection as Essential Tools for the Clinical Management of Chronic Myeloid Leukemia Patients: Results from a Brazilian Single-Center Study

Chronic myeloid leukemia (CML) is a well-characterized oncological disease in which virtually all patients possess a translocation (9;22) that generates the tyrosine kinase BCR::ABL1 protein. This translocation represents one of the milestones in molecular oncology in terms of both diagnostic and prognostic evaluations. The molecular detection of the BCR::ABL1 transcription is a required factor for CML diagnosis, and its molecular quantification is essential for assessing treatment options and clinical approaches. In the CML molecular context, point mutations on the ABL1 gene are also a challenge for clinical guidelines because several mutations are responsible for tyrosine kinase inhibitor resistance, indicating that a change may be necessary in the treatment protocol. So far, the European LeukemiaNet and the National Comprehensive Cancer Network (NCCN) have presented international guidelines on CML molecular approaches, especially those related to BCR::ABL1 expression. In this study, we show almost three years' worth of data regarding the clinical treatment of CML patients at the Erasto Gaertner Hospital, Curitiba, Brazil. These data primarily comprise 155 patients and 532 clinical samples. BCR::ABL1 quantification by a duplex-one-step RT-qPCR and ABL1 mutations detection were conducted. Furthermore, digital PCR for both BCR::ABL1 expression and ABL1 mutations were conducted in a sub-cohort. This manuscript describes and discusses the clinical importance and relevance of molecular biology testing in Brazilian CML patients, demonstrating its cost-effectiveness.