Defects in DBA: more than meets the eye

Can any patients with chronic myeloid leukemia outside of a clinical trial have their tyrosine kinase inhibitor discontinued?

PURPOSE OF REVIEW

This article critically appraises the state of treatment-free remission as a strategy for patients with chronic myeloid leukemia (CML) in deep remission after therapy with tyrosine kinase inhibitors (TKIs).

RECENT FINDINGS

Approximately half of patients with CML defined fairly narrowly by trial criteria - TKI sensitive, in deep molecular remission for a defined period - can successfully maintain protective levels of response after TKI cessation. Those who cannot appear at very low risk of disease control loss and can promptly regain remission with TKI resumption. Increasing numbers of patients followed longer term in trials have proven as well as a lack of additional late relapse in either group and that 'functional cure' of CML is feasible. Both the definition of remission sufficient to attempt treatment-free remission and the trigger to resume treatment have been relaxed somewhat while outcomes have remained the same. Based on repeated confirmatory data, economic pressures, and pragmatism, the question of feasibility and safety of TKI cessation outside of clinical trials is at hand.

SUMMARY

TKI cessation outside of clinical trials, if performed under strict guidelines, utilizing optimal monitoring techniques, with counsel available from experts in the field, and after full disclosure of the risks and benefits with the patient, may be safe (see video, supplemental digital content 1, which summarizes the abstract and offers the author's perspective,http://links.lww.com/COH/A15).

Discontinuing Tyrosine Kinase Inhibitor Therapy in Chronic Myelogenous Leukemia: Current Understanding and Future Directions

BCR-ABL1 tyrosine kinase inhibitors (TKIs) have dramatically transformed the treatment of patients with chronic myelogenous leukemia (CML). Given the impressive and sustained response to TKI therapy that the majority of treated patients with CML enjoy, recent studies have explored the potential to achieve treatment-free remission in select patients, which may allow these patients to escape the adverse clinical and financial effects associated with life-long TKI therapy. The results of multiple prospective trials have demonstrated that patients who maintain a deep molecular response for at least 2 years with TKI treatment may be eligible for trial of TKI discontinuation. Mounting data indicates that approximately 40% of those who discontinue therapy on trial will remain in remission at least 1 year after TKI discontinuation; the majority of patients with molecular recurrence relapse within the first 6 months after TKI discontinuation, and TKI retreatment is highly effective in restoring response. Sokol score, duration of TKI therapy, depth of molecular response, and the presence of natural killer cells may all be associated with a higher probability of attaining treatment-free remission. Moving forward, emerging data from ongoing TKI discontinuation trials will allow for appropriate selection of patients with CML eligible for this approach, will expand our current understanding of the CML stem cell, and identify therapeutic interventions capable of effectively deleting the malignant hematopoietic stem cell.

Discontinuation of dasatinib in patients with chronic myeloid leukaemia who have maintained deep molecular response for longer than 1 year (DADI trial): a multicentre phase 2 trial

BACKGROUND

First-line imatinib treatment can be successfully discontinued in patients with chronic myeloid leukaemia after deep molecular response has been sustained for at least 2 years. We investigated the safety and efficacy of discontinuing second-line or subsequent dasatinib after at least 1 year of deep molecular response.

METHODS

The Dasatinib Discontinuation trial was a prospective multicentre trial done in Japan. Eligible patients taking dasatinib and with confirmed stable deep molecular response were enrolled between April 1, 2011, and March 31, 2012. All patients received dasatinib consolidation therapy for at least 1 year. In those with sustained deep molecular response, dasatinib was discontinued. Patients were followed up every month in year 1 (clinical cutoff), every 3 months in year 2, and every 6 months in year 3 for deep molecular response and immunological profiles. The primary endpoint was the proportion of patients with treatment-free remission at 6 months after discontinuation. Molecular relapse was defined as loss of deep molecular response at any assessment. This study is registered, number UMIN000005130.

FINDINGS

88 patients were enrolled in the consolidation phase, 24 were excluded from the discontinuation phase due to fluctuations in BCR-ABL1 transcript levels. One patient was excluded because of positive expression of major and minor BCR-ABL1 transcripts in chronic myeloid leukaemia cells and the detection of minor BCR-ABL1 transcripts during consolidation. Thus, 63 patients discontinued dasatinib treatment. The 25 patients who were excluded from discontinuation continued to receive dasatinib and none showed disease progression. Median follow-up was 20.0 months (IQR 16.5-24.0). Of the 63 patients who discontinued and were not excluded, 30 patients maintained deep molecular response while 33 patients had molecular relapses, all within the first 7 months after discontinuation. The estimated overall treatment-free remission was 49% (95% CI 36-61) at 6 months. No severe treatment-related toxic effects were seen. Treatment was restarted in the 33 patients with relapse; rapid molecular responses were seen in all 33 patients, of whom 29 (88%) regained deep molecular response within 3 months, as did the remaining four by 6 months.

INTERPRETATION

Dasatinib discontinuation after sustained deep molecular response for more than 1 year is feasible.

FUNDING

Epidemiological and Clinical Research Information Network (ECRIN).

Killer immunoglobulin-like receptors can predict TKI treatment-free remission in chronic myeloid leukemia patients

Several factors are predictive of treatment-free remission (TFR) in chronic myeloid leukemia (CML), but few data exist on the role of natural killer (NK) cells and their killer-cell immunoglobulin-like receptors (KIRs). KIR and human leukocyte antigen (HLA) genotypes were investigated in 36 CML patients who discontinued tyrosine kinase inhibitor (TKI) treatment after achieving deep molecular response (MR(4.5)). Cumulative TFR was significantly higher in patients homozygous for KIR A haplotype (85.7% vs. 45.5%; p = 0.029). Younger age, Bx haplotype, and the combination KIR3DS1/KIR3DL1 present/HLA-Bw4 present were significantly associated with relapse. KIR genotypes could prove useful in identifying patients that are likely to maintain MR(4.5) after discontinuing TKI treatment.