Kinetics of early and late molecular recurrences after first-line imatinib cessation in chronic myeloid leukemia: updated results from the STIM2 trial

Treatment-free remission after discontinuation of tyrosine kinase inhibitors in patients with chronic myeloid leukemia in the chronic phase: a systematic review and meta-analysis

BACKGROUND

Treatment-free remission (TFR) is a new long-term goal for treating selected patients with chronic myeloid leukemia in the chronic phase (CML-CP). Still, the appropriate group in which TFR can be attempted and the factors influencing it have not yet been identified. This meta-analysis aimed to explore TFR in CML-CP patients who achieved a deep molecular response (DMR) before Tyrosine kinase inhibitors (TKIs) discontinuation and to explore possible factors influencing TFR and the safety of discontinuation.

METHODS

We performed a systematic review and single-arm meta-analysis with a systematic search of published literature up to September 2023 in PubMed, Embase, Web of Science, Cochrane Library, and CNKI databases. The assessment was performed using the MINORS scale. Random-effects models were used to calculate outcome metrics, including overall mean TFR rates at 12 and 24 months and subgroup differences. Data synthesis and analysis were done by Stata17.0 software.

RESULTS

A total of 19 single-arm trials involving 2336 patients were included in this meta-analysis, with an overall mean TFR rate of 59% [95CI:0.56-0.63] at 12 months and 55% [95CI:0.52-0.59] at 24 months, and no CML-related deteriorations or deaths reported during the TFR period. Our subgroup analysis showed that better TFR was associated with prior interferon therapy (P = 0.003), and molecular response depth MR5.0 (P = 0.020).

CONCLUSION

Our study demonstrated that prior interferon therapy and attainment of a molecular response depth of MR5.0 or greater were associated with higher TFR rates, with patients who attained MR5.0 or greater achieving a TFR rate of up to 62% in the second year after TKI discontinuation. Considering the high heterogeneity of the included trials, the above influences still require further validation and more detailed subgroup analysis in future discontinuation trials.

SYSTEMATIC REVIEW REGISTRATION

https://www.crd.york.ac.uk/prospero/ (Registration No. CRD42023471334).

The initial molecular response predicts the deep molecular response but not treatment-free remission maintenance in a real-world chronic myeloid leukemia cohort

In chronic myeloid leukemia, the identification of early molecular predictors of stable treatment-free remission (TFR) after tyrosine kinase inhibitor (TKI) discontinuation is challenging. The predictive values of residual disease (BCR::ABL1 quantification) at month 3 and 6 and more recently, BCR::ABL1 transcript halving time (HT) have been described, but no study compared the predictive value of different early parameters. Using a real-world cohort of 408 patients, we compared the performance of the EUTOS long-term survival (ELTS) score, BCR::ABL1 HT, and residual disease at month 3 and 6 to predict the molecular response, achievement of the TKI discontinuation criteria, and TFR maintenance. The performances of BCR::ABL1 HT and residual disease at month 3 were similar. Residual disease at month 6 displayed the best performance for predicting the optimal response (area under the ROC curve between 0.81 and 0.92; cut-off values: 0.11% for MR4 at month 24 and 0.12% for MR4.5 at month 48). Conversely, no early parameter predicted reaching the TKI discontinuation criteria and TFR maintenance. We obtained similar results when patients were divided in subgroups by first-line treatment (imatinib vs. second-generation TKI [2G-TKI]). We identified a relationship between ELTS score, earlier milestones and TFR maintenance only in the 2G-TKI group. In conclusion, this first comparative study of early therapeutic response parameters showed that they are excellent indicators of TKI efficacy (BCR::ABL1 transcript reduction) and best responders. Conversely, they did not predict the achievement of the TKI discontinuation criteria and TFR maintenance, suggesting that other parameters are involved in TFR maintenance.

Treatment-free remission as a new goal in the management of chronic myeloid leukemia: Clinical and biological aspects

The therapeutic armamentarium of chronic myeloid leukemia (CML) has dramatically improved after small molecule tyrosine kinase inhibitors (TKIs) targeting BCR::ABL1 became available, with a life expectancy now close to that of the general population. Although highly effective, these drugs also have a toxicity profile that is often mild to moderate, but sometimes severe. Indeed, long-term treatment with TKIs can lead to chronic adverse events that can negatively affect patients' quality of life and can promote significant morbidity and mortality, particularly in the case of second- or third-generation TKIs. Treatment discontinuation has therefore become an emerging goal for CML patients and numerous studies have evaluated in off-TKI subjects what requirements are appropriate for an attempt at treatment-free remission (TFR). TFR eligibility is currently limited to a small population of subjects with both deep and sustained molecular responses to TKIs. For those attempting TFR, average success rates are promising, with 25%-30% of patients experiencing prolonged TFR. In case of failure to maintain sustained TFR, safety results to date are reassuring, with almost all patients responding successfully to resumption of TKIs, and advanced-phase disease progression representing a very rare event. The purpose of this review is to discuss guidelines for TKI discontinuation, clinical advances from clinical trials and real-life experiences, and describe areas of research, particularly regarding the biological factors capable of predicting the success of TFR.

The inherent fragility of collective proliferative control

Tissues achieve and maintain their sizes through active feedback, whereby cells collectively regulate proliferation and differentiation so as to facilitate homeostasis and the ability to respond to disturbances. One of the best understood feedback mechanisms-renewal control-achieves remarkable feats of robustness in determining and maintaining desired sizes. Yet in a variety of biologically relevant situations, we show that stochastic effects should cause rare but catastrophic failures of renewal control. We define the circumstances under which this occurs and raise the possibility such events account for important non-genetic steps in the development of cancer. We further suggest that the spontaneous stochastic reversal of these events could explain cases of cancer normalization or dormancy following treatment. Indeed, we show that the kinetics of post-treatment recurrence for many cancers are often better fit by a model of stochastic re-emergence due to loss of collective proliferative control, than by deterministic models of cancer relapse.

European Stop Tyrosine Kinase Inhibitor Trial (EURO-SKI) in Chronic Myeloid Leukemia: Final Analysis and Novel Prognostic Factors for Treatment-Free Remission

Clinical trials frequently include multiple end points that mature at different times. The initial report, typically based on the primary end point, may be published when key planned co-primary or secondary analyses are not yet available. Clinical Trial Updates provide an opportunity to disseminate additional results from studies, published in JCO or elsewhere, for which the primary end point has already been reported.The European Stop Kinase Inhibitors (EURO-SKI) study is the largest clinical trial for investigating the cessation of tyrosine kinase inhibitors (TKIs) in patients with chronic myeloid leukemia in stable deep molecular remission (DMR). Among 728 patients, 434 patients (61%; 95% CI, 57 to 64) remained in major molecular response (MMR) at 6 months and 309 patients of 678 (46%; 95% CI, 42 to 49) at 36 months. Duration of TKI treatment and DMR before TKI stop were confirmed as significant factors for the prediction of MMR loss at 6 months. In addition, the type of BCR::ABL1 transcript was identified as a prognostic factor. For late MMR losses after 6 months, TKI treatment duration, percentage of blasts in peripheral blood, and platelet count at diagnosis were significant factors in multivariate analysis. For the entire study period of 36 months, multiple logistic regression models confirmed duration of treatment, blasts, and transcript type as independent factors for MMR maintenance. In addition to the duration of treatment, transcript type as well as blasts in peripheral blood at diagnosis should be considered as important factors to predict treatment-free remission.

Exploration of treatment-free remission in CML, based on molecular monitoring

BACKGROUND

Typical chronic myelogenous leukemia (CML) is a myeloproliferative neoplasm caused by t(9; 22)(q34; q11) translocation. This chromosomal translocation forms the BCR::ABL1 fusion gene. The tyrosine kinase encoded by the BCR::ABL1 is considered to be the main pathogenic diver. BCR::ABL1 is not only a therapeutic target, but also a monitoring target. Monitoring of BCR::ABL1 reveals the progression of the disease and guides the next treatment. Now for CML, the target of treatment has been focused on treatment-free remission (TFR).

METHODS

We conducted a literature review of current developments of treatment-free remission and molecular monitoring methods.

RESULTS

More effective and sensitive CML monitoring methods such as digital droplet PCR (ddPCR) and next generation sequencing (NGS) have further studied the measurable residual disease (MRD) and clonal heterogeneity, which provides strong support for the exploration of TFR. We discussed some of the factors that may be related to TFR outcomes at the molecular level, along with some monitoring strategies.

CONCLUSION

Currently, predictive indicators for treatment-free remission outcomes and recurrence are lacking in clinical practice. In future, treatment-free remission research should focus on combining the clinical indicators with molecular monitoring and biological markers to personalize patient conditions and guide clinicians to develop individualized treatment plans, so that more patients with CML can achieve safer and stabler treatment-free remission.

Advances in droplet digital polymerase chain reaction on microfluidic chips

The PCR technique has been known to the general public since the pandemic outbreak of COVID-19. This technique has progressed through three stages: from simple PCR to real-time fluorescence PCR to digital PCR. Among them, the microfluidic-based droplet digital PCR technique has attracted much attention and has been widely applied due to its advantages of high throughput, high sensitivity, low reagent consumption, low cross-contamination, and absolute quantification ability. In this review, we introduce various designs of microfluidic-based ddPCR developed within the last decade. The microfluidic-based droplet generation methods, thermal cycle strategies, and signal counting approaches are described, and the applications in the fields of single-cell analysis, disease diagnosis, and pathogen detection are introduced. Further, the challenges and prospects of microfluidic-based ddPCR are discussed. We hope that this review can contribute to the further development of the microfluidic-based ddPCR technique.