Molecular responses of late chronic phase chronic myeloid leukemia patients after achieving complete cytogenetic responses with imatinib treatment: a 6-year follow-up

Second-generation tyrosine kinase inhibitors combined with stem cell transplantation in patients with imatinib-refractory chronic myeloid leukemia

BACKGROUND

Allogeneic stem cell transplantation (allo-SCT) remains a curative therapy for chronic myeloid leukemia with advanced diseases, but limited data exist on the efficacy of short-time 2nd-generation tyrosine kinase inhibitors (TKIs) used before and after allo-SCT for patients failing imatinib therapy.

METHODS

We present a single-center report of a series of 12 imatinib-refractory patients in advanced phases, 9 of whom harbored BCR-ABL1 mutations. All of them were treated with 2nd TKI, followed by allo-SCT.

RESULTS

Dasatinib or nilotinib reinduced complete hematologic responses in 11 patients and complete cytogenetic responses in 4 patients. All patients engrafted successfully. Five patients experienced acute graft-versus-host-disease (GVHD), including 4 with grade III-IV disease. Four patients experienced chronic GVHD, including 1 with extensive disease. Post-transplant prophylactic dasatinib or nilotinb was administrated in 9 patients and discontinued 1 year later, all of whom sustained complete molecular remission, even after a median follow-up of 13 months after withdrawal of the TKI. No hematologic relapse was observed. Four patients died: 1 of primary disease and 3 of transplant-related complications. After a median follow-up of 28 months (range, 12-37 months) after SCT, 8 (66.7%) of 12 patients are alive, including 7 with complete molecular remission.

CONCLUSIONS

Allo-SCT has a satisfactory outcome when combined with 2nd-generation TKI, which could provide a good quality of remission before transplantation and prevent relapse after transplantation.

Clinical efficacy and safety of imatinib in the management of Ph(+) chronic myeloid or acute lymphoblastic leukemia in Chinese patients

Imatinib mesylate is considered the standard first-line systemic treatment for patients with chronic myeloid leukemia (CML) and functions by targeting BCR-ABL tyrosine kinases. Imatinib has substantially changed the clinical management and improved the prognosis of CML and Philadelphia chromosome-positive acute lymphocytic leukemia (Ph⁺ ALL). Here, we review the pharmacology, mode of action, and pharmacokinetics of imatinib; Chinese efficacy studies in CML and Ph⁺ ALL; safety and tolerability; patient-focused perspectives, such as quality of life, patient satisfaction, acceptability, and adherence; and uptake of imatinib.

Evaluation of long-term outcomes, cytogenetic and molecular responses with imatinib mesylate in early and late chronic-phase chronic myeloid leukemia: a report from a single institute

Here we compare the management and survival outcomes of chronic myeloid leukemia (CML) patients who had early or late imatinib mesylate (IM) therapy. The cytogenetic and molecular responses of 189 CML patients were analyzed. Of this group, 121 patients were classified as the early chronic phase (ECP) group and started IM within 12 months of diagnosis. The other 68 patients were classified as the late chronic phase (LCP) group who had been treated with interferon (IFN)-alpha-2 and crossed over to IM more than 12 months after diagnosis. The overall rates of complete cytogenetic response (CCyR) and major molecular response (MMR) at last follow-up were 83.6 and 78.1% in the ECP and LCP groups, respectively. The CCyR rates were 89.3 (for ECP patients) versus 73.5% (for LCP patients; p < 0.0001). At last follow-up, 82.4% ECP and 64.2% LCP patients had achieved an MMR (p < 0.0001). No significant differences were noted between the two groups with regard to survival outcomes. Our experience reveals that IM is an effective rescue therapy in most CML LCP patients who are intolerant or in whom IFN-alpha therapy fails. Such therapeutic options should be considered in LCP patients, particularly in countries where IM may not be available.

Molecular resistance: an early indicator for treatment change?

Vigilant monitoring of a patient's response to current treatment is imperative to the management of chronic myeloid leukemia (CML). Early identification of treatment failure may increase the probability that alternative therapy will be effective. This review discusses the use of molecular monitoring in the timely detection of failure of imatinib treatment. Changes in the levels of BCR-ABL transcripts are predictive of response or relapse. Patients achieving a major molecular response (MMR) within 12 months of treatment may experience longer cytogenetic remission. Accumulating evidence also suggests that lower transcript levels observed ≤ 6 months after the start of treatment are associated with improved patient outcomes. For patients with primary or secondary imatinib resistance (or intolerance), dasatinib or nilotinib may be prescribed. These agents have demonstrated activity in patients harboring imatinib-resistant BCR-ABL mutations, except for the T315I substitution.

Measuring response to BCR-ABL inhibitors in chronic myeloid leukemia

In patients with chronic myeloid leukemia (CML), the hallmark Philadelphia chromosome is the marker of disease that can be detected by conventional metaphase cytogenetics, fluorescence in situ hybridization, or polymerase chain reaction. The current "gold standard" of treatment response is cytogenetic response. Cytogenetic response to imatinib is strongly associated with disease progression and survival. Various strategies aimed at improving cytogenetic response have been explored, such as escalation of imatinib and switching to the newer breakpoint cluster region/v-abl Abelson murine leukemia viral oncogene (BCR-ABL) inhibitors dasatinib and nilotinib. Data from recent randomized trials of dasatinib and nilotinib as first-line therapy of newly diagnosed chronic-phase CML suggest that these agents are more effective than imatinib in achieving 6-month and 12-month complete cytogenetic responses. However, it is still too early to know whether or not this early response will translate into a long-term survival advantage. In addition, more sensitive assays to detect residual disease also may be associated with improved long-term outcomes. The deepest measure of response-a complete molecular response-may help identify patients who can stop taking imatinib for the short term, although the long-term consequences of this strategy remain unknown.

Characteristics of BCR-ABL kinase domain point mutations in Chinese imatinib-resistant chronic myeloid leukemia patients

To explore the characteristics of BCR-ABL kinase domain point mutations in Chinese chronic myeloid leukemia (CML) patients, a cohort of 127 patients with hematologic or cytogenetic resistance to imatinib are screened by direct sequencing. Mutations are found in 74 patients (58%). More patients with hematologic resistance show mutations compared to patients with cytogenetic resistance (70% vs 44%, p = 0.002), and more patients with acquired resistance present mutations compared to patients with primary resistance (68% vs 48%, p = 0.031). Frequencies of mutations were similar in early chronic phase (ECP), late chronic phase (LCP), accelerated phase, and blast phase (BP) patients (56%, 58%, 50%, and 69%, respectively; p > 0.05). Overall, 25 mutants are found in 21 amino acid sites, and four of them (I418V, E450A, E453L, and E455K) are first reported here. All patients with these four mutants either progress to or reenter the BP. The most frequent mutant is M244V, followed by Y253H, F359C/V/I, G250E, E255K, and T315I. Only seven patients (9%) have T315I mutants, and all showed hematologic resistance. Three of them were in the ECP and three in the LCP. Look-back studies show that mutants were detected 0-20 (median 7) months ahead of the appearance of clinical resistance in 15 tested patients with acquired resistance. ABL mutations are common in Chinese imatinib-resistant CML patients and are associated with clinical resistance. Chinese patients also seem to have unique profiles in the types and frequencies of some mutants, the disease phases of patients with T315I mutation, and the frequency of mutations in CP patients.

Dasatinib-associated major molecular responses in patients with chronic myeloid leukemia in chronic phase following imatinib failure: response dynamics and predictive value

Dasatinib is a highly potent BCR-ABL inhibitor that has shown durable efficacy in patients with chronic phase (CP) chronic myeloid leukemia (CML) after resistance, suboptimal response, or intolerance to prior imatinib. In patients with CML, BCR-ABL transcript measurement is the most sensitive method for assessing minimal residual disease. Here, molecular responses were analyzed in 1067 patients with CML-CP treated with dasatinib during phase II/III trials. After 3, 6, 12, and 24 months of follow-up, a major molecular response (MMR) was achieved by 12, 22, 35, and 40% of patients, respectively. The 24-month MMR rate was 34% in patients with resistance or suboptimal response to imatinib (n=829) and 63% in imatinib-intolerant patients (n=238). Among patients who had achieved a complete cytogenetic response (CCyR), 72% also achieved MMR. Responses with dasatinib 100 mg once daily were similar to other doses. In landmark analyses, 24-month progression-free survival was higher in patients who had achieved MMR or CCyR at 12 months than in those without MMR or CCyR at 12 months. MMR at 12 months was associated with a longer duration of CCyR. Overall, this analysis shows that dasatinib treatment results in high MMR rates in patients with CML-CP after imatinib failure.