Omitting cytogenetic assessment from routine treatment response monitoring in chronic myeloid leukemia is safe

Digital PCR for BCR-ABL1 Quantification in CML: Current Applications in Clinical Practice

Molecular monitoring of the BCR-ABL1 transcript for patients with chronic phase chronic myeloid leukemia (CML) has become increasingly demanding. Real-time quantitative PCR (qPCR) is the routinely used method, but has limitations in quantification accuracy due to its inherent technical variation. Treatment recommendations rely on specific BCR-ABL1 values set at timed response milestones, making precise measurement of BCR-ABL1 a requisite. Furthermore, the sensitivity of qPCR may be insufficient to reliably quantify low levels of residual BCR-ABL1 in patients in deep molecular response (DMR) who could qualify for an attempt to discontinue Tyrosine Kinase Inhibitor (TKI) therapy. We reviewed the current use of digital PCR (dPCR) as a promising alternative for response monitoring in CML. dPCR offers an absolute BCR-ABL1 quantification at various disease levels with remarkable precision and a clinical sensitivity reaching down to at least MR5.0. Moreover, dPCR has been validated in multiple studies as prognostic marker for successful TKI treatment discontinuation, while this could not be achieved using classical qPCR. dPCR may thus prospectively be the preferred method to reliably identify patients achieving treatment milestones after initiation of TKI therapy as well as for the selection and timing for TKI discontinuation.

Tyrosine Kinase Inhibitors in the Treatment of Chronic-Phase CML: Strategies for Frontline Decision-making

PURPOSE OF REVIEW

Over the past two decades, the introduction of tyrosine kinase inhibitors (TKIs) has transformed the treatment of chronic myeloid leukemia (CML). With four agents currently approved for frontline use in chronic-phase (CP) disease, it follows that treatment decision-making has been rendered more challenging. Here we will review recent advances that help inform the selection of a first-line TKI.

RECENT FINDINGS

Extended follow-up of the seminal CML trials has demonstrated the long-term efficacy of TKIs, while also highlighting significant differences in their respective toxicity profiles and potency. Dasatinib and nilotinib generate deeper molecular responses than imatinib, particularly among patients with higher risk disease, but this has not translated into a significant survival advantage. Similar results have been obtained at 1 year with bosutinib; its efficacy and toxicity were well balanced at a dose of 400 mg daily, prompting its recent approval for this indication. Lastly, multiple studies have demonstrated that TKIs can be safely discontinued in select individuals who have maintained deep responses for extended periods, establishing treatment-free remission as a novel goal in CP CML. The careful consideration of parameters such as disease risk, the potency, and toxicity profile of each TKI, as well as each patient's unique comorbidities and preferences, enables truly individualized therapeutic decision-making in CP CML, with the goal of ensuring that a high quality of life accompanies the survival advantage conferred by these agents.