Managing chronic myeloid leukemia patients intolerant to tyrosine kinase inhibitor therapy

The outcomes for patients with chronic myeloid leukemia have improved dramatically with the development and availability of BCR–ABL1 tyrosine kinase inhibitors (TKIs) over the past decade. TKI therapy has a superior safety profile compared with the previous standard of care, interferon-α, and most adverse events (AEs) observed with front-line and second-line TKI treatment are managed with supportive care. However, some patients are intolerant to TKI therapy and experience AEs that cannot be managed through dose reduction or symptomatic treatment. Careful management of AEs helps patients to remain adherent with treatment and increases their chances for successful outcomes. Proactive vigilance for potential AEs and treatment strategies that reduce symptom burden will help to minimize patient intolerance. This review discusses the most common AEs associated with intolerance to TKI therapy and treatment strategies to help manage patients at risk for or experiencing these events.     

Pregnancies in patients with chronic myeloid leukemia treated with tyrosine kinase inhibitor

We presented our experience in chronic myeloid leukemia (CML) patients who conceived children and/or became pregnant while receiving tyrosine kinase inhibitor (TKI). Among 7 male patients, 7 pregnancies resulted in the birth of 7 healthy babies. Among 18 female patients, 8 ended in elective abortion; 3 had spontaneous abortion, and 7 carried to term, resulting in the birth of 8 healthy babies. All children have normal growth and development. All patients remain in TKI therapy and in good response. It is suggested that female patients are advised to practice adequate contraception. No special precautions apply for male patients receiving TKI.     

Predictive indicators of successful tyrosine kinase inhibitor discontinuation in patients with chronic myeloid leukemia

Clinical trials have demonstrated that some patients with chronic myeloid leukemia (CML) treated for several years with tyrosine kinase inhibitors (TKIs) who have maintained a molecular response can successfully discontinue treatment without relapsing. Treatment free remission (TFR) can be reached by approximately 50% of patients who discontinue. Despite having similar levels of deep molecular response and an identical duration of treatment, the factors that influence the successful discontinuation of CML patients remain to be determined. In this review we will explore the factors identified to date that can help predict whether a patient will successfully achieve TFR. We will also discuss the need for the identification of predictive biomarkers associated with a high probability of achieving TFR for the future personalized identification of patients who are suitable for the discontinuation of TKI treatment.     

The effect of interleukin 11 on thrombocytopenia associated with tyrosine kinase inhibitor therapy in patients with chronic myeloid leukemia

BACKGROUND.: During therapy with tyrosine kinase inhibitors (TKIs), approximately 20% to 50% of patients with chronic myeloid leukemia (CML) develop grade >/=3 thrombocytopenia leading to treatment interruptions and dose reductions. Interleukin 11 (IL-11) reduces the incidence and the severity of thrombocytopenia in solid tumors. METHODS.: The authors investigated the efficacy and safety of low-dose IL-11 for improving thrombocytopenia associated with TKI therapy in 14 patients with CML. The starting dose of IL-11 was 10 mug/kg 3 times weekly, and the dose was escalated by 1 dose level every 2 weeks if the patients had no sustained platelet increase. RESULTS.: The median patient age was 52 years. The median platelet count at the time IL-11 was started was 37 x 10(9)/L. All patients had prior TKI dose reductions. After the initiation of IL-11, 8 of 14 patients (57%) had an increase in platelet count with a median peak platelet count of 110 x 10(9)/L. One additional patient had no platelet increase but was able to tolerate an imatinib dose increase. Eleven patients had a decrease in the number of days of TKI therapy interruption secondary to thrombocytopenia after the initiation of IL-11 (6% of total treatment time vs 34% of total treatment time before IL-11). Therapy was well tolerated. CONCLUSIONS.: The current results indicated that IL-11 may correct thrombocytopenia associated with TKI therapy for patients with CML and that it has a favorable toxicity profile. Cancer 2008. (c) 2008 American Cancer Society.     

Survival outcomes for clonal evolution in chronic myeloid leukemia patients on second generation tyrosine kinase inhibitor therapy

BACKGROUND:

Clonal evolution is frequently detected in patients developing resistance to imatinib. The outcome of patients with clonal evolution treated with second generation tyrosine kinase inhibitors is not known.

METHODS:

The authors analyzed the outcome of 177 CML patients after second tyrosine kinase inhibitor therapy.

RESULTS:

Ninety‐five patients were in chronic phase, 30 had clonal evolution, 28 were in accelerated phase (AP), and 24 were in AP plus clonal evolution. Major cytogenetic response rates were 58%, 54%, 28%, and 13%; 2‐year overall survival (OS) rates were 86%, 73%, 68%, and 33%; and 2‐year event‐free survival (EFS) rates were 69%, 67%, 31%, and 8%, respectively. The hematologic and cytogenetic response rates, OS, and EFS were no different between patients in chronic phase with clonal evolution and patients with chronic phase and no clonal evolution. However, clonal evolution had a significant adverse impact when associated with other features of AP. On multivariate analysis, clonal evolution had no independently significant effect on achieving major cytogenetic response on the second generation tyrosine kinase inhibitors. The factors predicting increasing major cytogenetic response to second generation tyrosine kinase inhibitors were prior achievement of major cytogenetic response with imatinib, higher hemoglobin levels, no splenomegaly, lower percentage of Philadelphia chromosome‐positive metaphases, and no prior chemotherapy.

CONCLUSIONS:

Clonal evolution constitutes a heterogeneous entity with variable outcome with second generation tyrosine kinase inhibitors, with trisomy 8, chromosome 17, and complex abnormalities having the worst outcome, regardless of the number of metaphases involved. The molecular events behind these abnormalities and potential therapeutic approaches directed at them need to be defined. Cancer 2010. © 2010 American Cancer Society.     

Adherence to oral tyrosine kinase inhibitor therapies in chronic myeloid leukemia

Ensuring adherence to therapy is a challenge in chronic diseases, particularly in cancers such as chronic myeloid leukemia (CML), where there has been increased availability and use of oral formulations. A conceptual model of adherence was developed based on findings from a comprehensive literature review, to inform strategies for improving adherence to oral CML therapies. A complex interplay of factors (including clinical, psychological and behavioural) influence adherence to such therapies. Healthcare professionals have a key role in promoting and facilitating adherence and future strategies should place greater emphasis on understanding patient-level experiences in order to create personalized solutions.     

Second-generation tyrosine kinase inhibitors as therapy for chronic myeloid leukemia

Chronic myeloid leukemia (CML) was the first human malignancy to be associated with a single genetic abnormality, characterized by a reciprocal translocation involving chromosomes 9 and 22 (the Philadelphia chromosome). The fusion gene that results (BCR-ABL) produces a constitutively activated tyrosine kinase that exists in different isoforms depending on BCR break-points. Imatinib mesylate is a highly selective inhibitor of this kinase, producing normal blood-counts in 98% of patients in chronic phase CML and disappearance of the Philadelphia chromosome in 86%. However, 17% of patients in the chronic phase will either relapse or develop resistance resulting mainly from one or more point mutations affecting at least 30 amino acids within the Abl kinase protein. This review focuses on the relevant biology of CML, imatinib mesylate resistance mechanisms, and the current status of the next generation of Bcr-Abl inhibitors.     

Secondary breast carcinoma after completely remitted chronic myeloid leukemia following targeted tyrosine kinase inhibitor therapy

We describe a rare case of secondary breast carcinoma after chronic myeloid leukemia (CML) in a 56-year-old woman. The patient was treated with hydroxyurea and imatinib for CML and achieved complete remission (she has since been taking imatinib as the maintenance therapy). Four years later, the patient noticed a firm and painless lump in the left breast, which was diagnosed as ductal carcinoma in situ based on a percutaneous biopsy of the mass. Simple resection and sentinel lymph node biopsy of the left breast were then performed. Pathological studies revealed a medium-grade intraductal carcinoma, with local infiltration associated with invasive micropapillary carcinoma. She received adjuvant endocrine therapy with imatinib after surgery. Breast cancer secondary to CML (treated with imatinib and completely remitted) is extremely rare. This report provides evidence to assist in the diagnosis and treatment for this rare manifestation.     

Treatment adherence in chronic myeloid leukaemia patients receiving tyrosine kinase inhibitors

Failure to comply with treatment recommendations is very common in patients, but still poorly recognised by doctors. The current practice of using oral therapy on a large scale has been increasingly adopted for cancer patients. Chronic myeloid leukaemia (CML) is just such an example, where the introduction of taking new oral medications, the tyrosine kinase BCR-ABL inhibitors (TKI), has now revolutionised the treatment. The aim of our study was to assess treatment adherence in a group of Polish CML patients (a survey was conducted on 140 patient aged ≥18 years) treated with oral TKI (imatinib, dasatinib and nilotinib) taking into account the following variables: gender, age, education, place of residence, family circumstances and duration of therapy. In addition, we evaluated whether there is a relationship between how patients perceive their level of adherence to treatment recommendations with how subjectively the required dosage regimen was followed. Half the patients admitted to skipping at least one drug dose during the entire course of treatment and 39% did so within their last treatment month. Patients were also found to overestimate their own adherence assessment; around 60% of those missing at least 1 drug dose within the last treatment month believed they ‘always’ followed recommendations. The study demonstrated that adherence deteriorates over time. Furthermore, patients aged >65 years and patients suffering at least one comorbid disease had better adherence (p < 0.011). There were no differences in adherence among patients treated with imatinib, dasatinib and nilotinib (p = 0.249).     

Current event‐free survival after sequential tyrosine kinase inhibitor therapy for chronic myeloid leukemia

BACKGROUND:

Imatinib is an effective tyrosine kinase inhibitor (TKI) for patients with chronic myeloid leukemia (CML) in chronic phase (CP). Although some patients may fail on therapy with imatinib, effective salvage therapy is available with second‐generation TKIs. Current measurement of efficacy for each therapy is judged by its individual impact on overall survival and event‐free survival (EFS).

METHODS:

In total, 586 patients with CML in CP who received imatinib were included in this analysis in 2 cohorts: imatinib as front‐line therapy (n = 281) or after failure on interferon‐α (IFN‐α) (n = 305). By accounting for successful salvage treatment (ie, regain of complete cytogenetic response), the current EFS (CEFS) rate was calculated to obtain a more accurate impression of the outcome of patients with CML who received treatment with sequential TKIs.

RESULTS:

For patients who received imatinib after failing on IFN‐α, the 7‐year EFS rate was 61%, whereas the CEFS rate was 69%. The 7‐year EFS rate for patients who received imatinib as initial therapy was 81% compared with a 7‐year CEFS rate of 88%.

CONCLUSIONS:

CEFS provided a more accurate representation of the outcome of patients with CML in CP. These patients may frequently be treated successfully with subsequent TKIs after experiencing failure on the first TKI. Cancer 2011. © 2010 American Cancer Society     

Practical advice for determining the role of BCR-ABL mutations in guiding tyrosine kinase inhibitor therapy in patients with chronic myeloid leukemia

Data demonstrating the superiority of nilotinib over imatinib in the frontline treatment of chronic myeloid leukemia (CML) and ongoing studies with dasatinib and bosutinib are rapidly changing the treatment landscape for CML. In this review, the authors discuss currently available therapies for CML, focusing on mechanisms of resistance to imatinib and treatment strategies to overcome resistance. Relevant articles were identified through searches of PubMed and abstracts from international hematology/oncology congresses. Additional information sources were identified from the bibliographies of these references and from the authors' own libraries and expertise. In vitro 50% inhibitory concentration (IC(50) ) data alone are not sufficient to guide the choice of a tyrosine kinase inhibitor (TKI) in the presence of a mutant breakpoint cluster region-v-abl Abelson murine leukemia viral oncogene homolog (BCR-ABL) clone, because there is a lack of data regarding how well such IC(50) values correlate with clinical response. A small subset of BCR-ABL mutant clones have been associated with impaired responses to second-generation TKIs (tyrosine to histidine mutation at codon 253 [Y253H], glutamic acid to lysine or valine mutation at codon 255 [E255K/V], and phenylalanine to cysteine or valine mutation at codon 359 [F359C/V] for nilotinib; valine to leucine mutation at codon 299 [V299L] and F317L for dasatinib); neither nilotinib nor dasatinib is active against the threonine to isoleucine mutation at codon 315 (T315I). For each second-generation TKI, the detection of 1 of a small subset of mutations at the time of resistance may be helpful in the selection of second-line therapy. For the majority of patients, comorbidities and drug safety profiles should be the basis for choosing a second-line agent. Clinical trial data from an evaluation of the response of specific mutant BCR-ABL clones to TKIs is needed to establish the role of mutation testing in the management of CML.     

Profiling chronic myeloid leukemia patients reporting intentional and unintentional non-adherence to lifelong therapy with tyrosine kinase inhibitors

The main objective of this study was to outline key characteristics, including health-related quality of life (HRQOL) and symptoms, in 175 chronic myeloid leukemia (CML) patients reporting intentional or unintentional reasons for not fully adhering to imatinib therapy. There was a significant higher proportion of males in the unintentional group (P = 0.037). Also, in this group patients were on average younger (P = 0.046). Patients reporting intentional reasons had generally a worse HRQOL profile and a higher symptom severity than those who reported unintentional reasons for non-adherence. This study suggests that patients with suboptimal adherence are not a homogenous group, thus generalized approaches to improve medication-taking behaviors are not recommended.     

Novel therapeutic approach to eradicate tyrosine kinase inhibitor resistant chronic myeloid leukemia stem cells

Although discovery of the tyrosine kinase inhibitor (TKI) imatinib mesylate has significantly improved the prognosis of chronic myeloid leukemia (CML) patients, a rare population of CML stem cells is known to be resistant to TKI therapy, causing recurrence of CML. However, recent progress in CML stem cell biology may present a novel therapeutic avenue for CML patients. In this review, we focus on mechanisms used by CML stem cells to maintain TKI‐resistance. Comprehensive approaches including mouse genetics, prospective identification of CML stem cells, and syngenic transplantation techniques have identified several key molecules or signaling pathways, including hedgehog (Hh)/Smo, promyelocytic leukemia (PML), 5‐lipoxygenase (5‐LO), and forkhead box class O (FOXO), that function in CML stem cell maintenance. Inhibiting some of these factors in combination with TKI administration successfully antagonized resistance of CML stem cells to TKI therapy, resulting in efficient eradication of leukemia cells in vivo. Thus, development of methods that sensitize CML stem cells to TKI therapy may lead to novel therapies to treat CML patients. (Cancer Sci 2010)     

Mechanisms and novel approaches in overriding tyrosine kinase inhibitor resistance in chronic myeloid leukemia

Chronic myeloid leukemia is a stem cell-initiated but progenitor-driven disease induced by the BCR-ABL oncogene. Tyrosine kinase inhibitors (TKIs) were introduced in the late 1990s and have revolutionized the management of chronic myeloid leukemia in chronic phase. The majority of patients can now expect to live a normal life as long as they continue to comply with TKI treatment. However, in a significant proportion of cases TKI resistance develops over time, requiring a switch of therapy. The most frequent mechanism for drug resistance is the development of kinase domain mutations that reduce or completely ablate drug efficacy. Fortunately, the last 10 years have seen an impressive array of new drugs, some modeled on the mechanism of action of imatinib, others employing more novel approaches, for these patients.     

Dual tyrosine kinase inhibitors in chronic myeloid leukemia.

The Bcr-Abl inhibitor imatinib mesylate induces complete hematologic and cytogenetic remissions in most newly diagnosed chronic myeloid leukemia (CML) patients, but relatively few of them achieve molecular remission. In addition, imatinib is much less effective in advanced phase-CML as well as in Philadelphia-positive (Ph+) acute lymphoblastic leukemia (ALL), mainly due to the development of drug resistance. The challenge for the future is to improve current clinical results with kinase inhibitors in CML, developing strategies that can eradicate residual disease and overcome or prevent resistance. 'Dual' Src and Abl kinase inhibitors are an attractive class of compounds, since (a) these molecules are able to bind Bcr-Abl with less stringent conformational requirements with respect to imatinib, therefore allowing for efficient inhibition of several, resistance-associated mutant forms of Bcr-Abl; (b) Src kinases have been shown to be involved in Bcr-Abl-mediated leukemogenesis as well as upregulated in some patients resistant to imatinib. Here, we review the development, the mode of action and the preclinical or early clinical evaluation of several novel dual Src and Abl kinase inhibitors.     

Bosutinib: a third generation tyrosine kinase inhibitor for the treatment of chronic myeloid leukemia

Bosutinib is an oral tyrosine kinase inhibitor (TKI) with very potent dual inhibitory activity against SRC and abelson gene. Bosutinib was approved in 2012 for the treatment of resistant Philadelphia chromosome positive chronic myeloid leukemia (CML). Bosutinib is a very effective TKI against all phases of intolerant or resistant CML regardless of the presence or absence of an abelson gene domain mutation, except for cases with detectable T315I or V299L. Bosutinib is overall well tolerated and associated with a unique, but manageable toxicity profile. Factors that influence the prescribing pattern of this drug are complex and include physicians’, and increasingly patients and families’ preference, patients’ comorbid conditions, schedule of administration, as well as financial factors. This paper provides an overview of CML, the TKI market, pharmacokinetics, pharmacodynamics, clinical efficacy, safety and tolerability of bosutinib.     

Managing side effects of tyrosine kinase inhibitor therapy to optimize adherence in patients with chronic myeloid leukemia: the role of the midlevel practitioner

In the last decade, the development of imatinib, a tyrosine kinase inhibitor, has brought about unprecedented change in the way newly diagnosed, chronic-phase chronic myeloid leukemia patients are treated. Two next-generation tyrosine kinase inhibitors, nilotinib and dasatinib, were initially indicated for imatinib-resistant or imatinib-intolerant chronic myeloid leukemia patients and recently received approval from the Food and Drug Administration for treatment of newly diagnosed, chronic-phase chronic myeloid leukemia patients. In comparison with the previous standards of care, benefits with these three tyrosine kinase inhibitors have included more rapid response rates, increased survival, and fewer side effects. The improved long-term outcomes have altered the approach to management of chronic myeloid leukemia from a progressive fatal disease with a poor prognosis to a chronic condition similar to diabetes or hypertension. Prolonged survival increases the need for patient education, support, monitoring, and assistance with adverse event management. Even low-grade side effects can adversely affect patients' quality of life and, therefore, require prompt attention to prevent long-term complications or suboptimal outcomes. New evidence has indicated that patient adherence to tyrosine kinase inhibitor therapy is essential to successful treatment. Midlevel practitioners can help to optimize outcomes by educating patients regarding the importance of adherence, performing regular monitoring, helping patients to understand their test results, and aggressively managing treatment-related side effects.