Malignancies occurring during therapy with tyrosine kinase inhibitors (TKIs) for chronic myeloid leukemia (CML) and other hematologic malignancies

Success of tyrosine kinase inhibitors (TKIs) in chronic myeloid leukemia (CML) has given patients hope for a long disease-free-survival. A longer survival raises the question of late effects, including development of another malignancy. Records of 1445 patients with CML/myeloproliferative neoplasm or other hematologic malignancies treated with TKIs were reviewed to investigate frequency and characteristics of second malignancies (other than acute myeloid leukemia, acute lymphocytic leukemia, or myelodysplastic syndrome). The number of second cancers was compared with the number expected from the Surveillance, Epidemiology, and End Results database. After a median follow-up of 107 months (range, 13-362 months) after CML/myeloproliferative neoplasm diagnosis, 66 patients (4.6%) developed 80 second cancers, including skin (31%), prostate (15%), melanoma (13%), digestive system (10%), kidney (4%), thyroid (4%), breast (3%), chronic lymphocytic leukemia (3%), hepatobiliary (3%), and other cancers (14%). Excluding nonmelanoma skin cancers, 55 second cancers were seen in 51 (3.5%) of all patients treated. The risk of second cancer was lower than expected (observed-to-expected ratio, 0.6; 95% confidence interval, 0.44-0.81). Second cancers occur in a small percentage of patients receiving therapy with TKIs for hematologic malignancies, mostly CML. No evidence at the moment suggests that exposure to TKIs increases the risk of developing second cancers.     

New tyrosine kinase inhibitors in chronic myeloid leukemia

The deregulated activity of BCR-ABL tyrosine kinase originating from the t(9;22) chromosomal translocation has been shown to be necessary and sufficient for the transformed phenotype of chronic myeloid leukemia (CML) cells. This peculiarity has paved the way for the development of novel therapies specifically targeting the BCR-ABL gene product. The first BCR-ABL inhibitor to come into use in clinical practice, imatinib mesylate, is now the first-choice treatment for all newly diagnosed CML patients, but the initial striking efficacy of this drug has been overshadowed by the development of clinical resistance. The most common mechanisms of resistance include (i) BCR-ABL overexpression, and (ii) BCR-ABL kinase domain mutations disrupting critical contact points between imatinib and BCR-ABL or inducing a transition to a conformation to which imatinib is unable to bind. Several approaches to overcoming resistance have been studied both in vitro and in vivo. They include dose escalation of imatinib, the combination of imatinib with chemotherapeutic drugs, alternative BCR-ABL inhibitors, and inhibitors of kinases acting downstream of BCR-ABL such as Src kinases. Various novel tyrosine kinase inhibitors (TKI) have been synthesized and have now reached the pre-clinical or clinical phase. This review highlights the development of new TKI as specific molecularly targeted therapy and as the principal mechanisms for overcoming imatinib resistance.     

Incidence of second malignancies during treatment of chronic myeloid leukemia with tyrosine kinase inhibitors in the Czech Republic and Slovakia

Tyrosine kinase inhibitors (TKI) have completely changed the prognosis of patients with Ph+ chronic myeloid leukemia (CML). The occurrence of a second malignancy (SM) in CML patients successfully treated with TKI may significantly affect their prognosis. In a retrospective study of 1,038 patients with CML treated at 10 centers in the Czech Republic and Slovakia between 2000 and 2009, SM was detected in 35 (3.37%) patients after TKI therapy was initiated. The median intervals from the diagnosis of CML and from the start of TKI therapy to the diagnosis of SM were 58 months (range 2 - 214) and 32 months (range 1 - 102), respectively. The observed age-standardized incidence of SM after the start of TKI therapy was 8.95 / 1,000 person-years. Comparison of the incidence of SM in CML patients with population data was performed only for patients from the Czech Republic. The age-standardized incidence rate of all malignant tumors except non-melanoma skin cancers was 6.76 (95% CI: 6.74; 6.78) / 1,000 person-years in 2000 - 2007 while the incidence rate of SM in 708 CML patients from the Czech Republic treated with TKI was 9.84 (95% CI: 6.20; 13.48) / 1,000 person-years, i.e. 1.5-fold higher, although the difference was statistically insignificant. The distribution of SM types in CML patients treated with TKI was similar to that in the age-standardized general Czech population. The median overall survival (OS) of patients treated with TKI who also developed SM (57 months) was shorter than the OS of patients treated with TKI but not suffering from SM (median OS not reached, log rank test p < 0.001. Prospective long-term population-based studies in CML patients treated with TKI as first-line therapy are needed to determine the relationship of SM to KTI therapy.     

Efficacy of the farnesyl transferase inhibitor R115777 in chronic myeloid leukemia and other hematologic malignancies

We investigated the clinical activity of the farnesyl transferase inhibitor R115777 in 22 patients with chronic myelogenous leukemia (CML) in chronic, accelerated, or blastic phase and in 8 patients with myelofibrosis (MF) and 10 patients with multiple myeloma (MM). R115777 was administered at 600 mg orally twice daily for 4 weeks every 6 weeks. Seven patients with CML (6 in chronic phase, 1 in advanced phase) achieved complete or partial hematologic response. Four of them had a minor cytogenetic response. Responses were transient, with a median duration of 9 weeks (range, 3-23 weeks). Two patients discontinued therapy because of toxicity while in complete hematologic response. Two MF patients had a significant decrease in splenomegaly, one had normalization of white blood cell count and differential, and one became transfusion independent. One patient with MM had a reduction in monoclonal protein of 34%. Adverse events included nausea in 22 patients (55%; all grade 2 or lower) and fatigue in 19 (48%; grade 3 or higher in 1). Other grade 3 or 4 toxicities included skin rash (4 patients, 10%), peripheral neuropathy (2 patients, 5%), and liver toxicity (2 patients, 5%). Patients who responded to therapy had significantly higher plasma vascular endothelial growth factor (VEGF) concentrations prior to treatment than nonresponders. Plasma concentrations decreased significantly during therapy among responders. R115777 showed clinical activity in patients with CML and MF. The effect on VEGF needs to be further investigated to determine whether this might be a possible mechanism of action of R115777.     

Chronic myeloid leukemia and tyrosine kinase inhibitors

INTRODUCTION: Chronic myeloid leukemia is a myeloproliferative disorder clinically characterised by a triphasic course: after a chronic phase over a median time of 4 years, patients developed an accelerated phase, then a blastic phase, resulting in the patient's death with 3 to 6 months. PURPOSE: During the last past years, progress have been made in the understanding of the molecular mechanism responsible of leukemic growth. This has also provided support for a therapeutic improvement with the appearance of treatment such as tyrosine kinase inhibitors which specifically target the oncoprotein inside the leukemic cells. CONCLUSION: These treatments, such as STI571 or Glivec, are at present in clinical trials, and could be the medicines for the future. Thus, chronic myeloid leukemia is also a model for the development of the new therapeutic drugs.     

The BCR-ABLT315I mutation compromises survival in chronic phase chronic myelogenous leukemia patients resistant to tyrosine kinase inhibitors,in a matched pair analysis

The BCR-ABL T315I mutation confers resistance to currently licensed tyrosine kinase inhibitors in chronic myelogenous leukemia. However, the impact of this mutation on survival in early stages of disease, in chronic phase, has never been detailed. Using matched pair analysis, a cohort of 64 patients with chronic phase chronic myelogenous leukemia harboring a T315I mutation and resistant to imatinib mesylate was compared to a similar cohort of 53 chronic phase patients resistant to imatinib, but with no detectable T315I mutation, in the pre-ponatinib era. These patients were matched according to age at diagnosis, interval between disease diagnosis and start of imatinib treatment, and duration of imatinib therapy. Kaplan-Meier survival analyses demonstrated the significant negative impact of the presence of the T315I mutation on overall survival (since imatinib-resistance: 48.4 months for T315I⁺ patients versus not reached for T315I⁻ ones; P=0.006) and failure-free survival (since imatinib-resistance: 34.7 months for T315I⁺ patients versus not reached for T315I⁻ patients; P=0.003). In addition, Cox proportional hazard models adjusted on overall survival demonstrated the negative influence of the T315I mutation (P=0.02, HR=2.54). These results confirm early assumptions concerning the poor prognosis of chronic phase chronic myelogenous leukemia patients with the T315I mutation who are not eligible for allogeneic transplantation, and demonstrate the need for more therapeutic options.     

Results of allogeneic hematopoietic stem cell transplantation for chronic myelogenous leukemia patients who failed tyrosine kinase inhibitors after developing BCR-ABL1 kinase domain mutations

Hematopoietic stem cell transplantation (HSCT) is effective therapy for patients with chronic myelogenous leukemia (CML) but is now mostly indicated for patients who develop resistance to tyrosine kinase inhibitors (TKIs), which can be associated with point mutations in BCR-ABL1. We reviewed the outcomes of imatinib-resistant CML patients (chronic phase, n = 34; accelerated phase [AP], n = 9; and blast phase [BP], n = 4) who underwent HSCT and had BCR-ABL1 sequencing. Mutations were found in 19 patients (40%); 15 of 19 had advanced CML (AP + BP + second chronic phase). Patients with mutations were more likely to transform to AP/BP at time of imatinib failure (69% vs 35%, P = .03). Forty-two patients (89%) responded to HSCT: 32 (68%) had at least a major molecular response. The 2-year event-free survival was 36% and 58% (P = .05) for the mutant and nonmutant groups, respectively; and the 2-year overall survival was 44% and 76% (P = .02), respectively. HSCT is an important salvage option for TKI-resistant patients with or without BCR-ABL1 mutations. Patients with mutations were more likely to develop advanced disease and had worse outcomes after HSCT. HSCT should be considered early for patients deemed to have a low probability of responding to second-generation TKI.     

Persistent epstein-barr virus infection mimicking juvenile chronic myelogenous leukemia: immunologic and hematologic studies

Epstein-Barr virus (EBV) infections may induce a diverse clinical picture, ranging from the well characterized infectious mononucleosis (IM) syndrome to the rare X-linked lymphoproliferative syndrome. We describe two unrelated children, a 21-mo-old white boy and a 15-mo-old black girl, who presented with the clinical and laboratory findings characteristically seen in juvenile chronic myelogenous leukemia (JCML). Results of periodic serodiagnostic tests indicated that they likely have persistent infection with EBV. Both had elevated IgG antibody to viral capsid antigen (greater than or equal to 1:320) and antibody to early antigen (1:20-1:40) that have persisted for 3 yr of more. Both patients had EBV-specific suppressor cell activity, decreased natural killer cell activity, and diminished antibody- dependent cell-mediated cytotoxicity (ADCC) activity. These changes suggest an underlying defect in the immunoregulatory network controlling EBV infection. The patients have shown clinical improvement without treatment. It appears that EBV infections are capable of inducing symptoms similar to those seen in JCML. Careful evaluation for evidence of EBV infection in patients presenting with symptoms compatible with JCML seems warranted.     

Clinical impact of pretransplant use of multiple tyrosine kinase inhibitors on the outcome of allogeneic hematopoietic stem cell transplantation for chronic myelogenous leukemia

Tyrosine kinase inhibitors (TKIs) are widely used to treat patients with chronic myelogenous leukemia in the chronic phase (CML‐CP), and outcomes of TKI treatment for patients with CML‐CP have been excellent. Since multiple TKIs are currently available, second‐line or third‐line TKI therapy is considered for patients who are intolerant of or resistant to the previous TKI treatment. Therefore, allogeneic hematopoietic stem cell transplantation (allo‐HSCT) is considered only for patients with disease progression or for patients after treatment failure with multiple TKIs. To reflect the current clinical situation of patients with CML‐CP, we tried to clarify whether prior TKI treatment affects the outcome of allo‐HSCT. Data from 237 patients for whom the number of pretransplant TKIs varied from one to three were used for analysis. Before allo‐HSCT, 153 patients were treated with one TKI, 49 patients were treated with two TKIs and 35 patients were treated with three TKIs. In addition to conventional risk factors, i.e., disease status at transplantation and patient's age, the use of three TKIs before transplantation was identified as a significant adverse factor for prognosis. Nonrelapse mortality rate was higher in patients treated with three TKIs than in patients treated with one or two TKIs. Our results suggest that allo‐HSCT could be considered for young patients with CML‐CP who manifest resistance to second‐line TKI therapy and who have an appropriate donor.     

Response to tyrosine kinase inhibitors in chronic myeloid leukemia: experience from a west Asian developing country

Tyrosine Kinase inhibitors (TKIs) have dramatically changed the prospects for patients with chronic myeloid leukemia (CML); however, information on CML and response to TKIs from Asia are limited, particularly from West Asia, including Iraq. To address the latter issue we evaluated and monitored a cohort of 108 Iraqi patients diagnosed as chronic phase-CML, enrolled in a government-sponsored national program. The patients were all treated initially by imatinib mesylate. Ninety-two percent of patients had a complete hematological response, 38 % had a major molecular response, while 79 % had a major cytogenetic response after a median follow-up of 35.7 months. The 3-year Event-Free, Progression-Free, and Overall survival rates were 79.6, 87 and 98.1 %, respectively. A total of 26 patients (24.1 %) were shifted to an alternative TKI (Nilotinib). After one year of therapy in seventeen of the latter patients, 24 % had major molecular response. In conclusion, our results compare favorably with those reported from the West and some Asian countries, and have demonstrated the importance of molecular as well as cytogenetic monitoring, and confirmed the relative success of the national CML program in our country.     

Use of tyrosine kinase inhibitors in a patient with Brugada syndrome and chronic myeloid leukemia

The treatment and prognosis of chronic myeloid leukemia have dramatically changed since the introduction of tyrosine kinase inhibitors, but although several clinical trials have examined their safety with respect to heart function, no data are yet available about the use of these drugs in patients with Brugada syndrome. We report a case of Brugada syndrome diagnosed during tyrosine kinase inhibitor therapy in a 69-year-old Caucasian male with meningioma and chronic myeloid leukemia. This case report highlights the importance of an integrated approach among hematologists and cardiologists to ensure appropriate treatment with tyrosine kinase inhibitors in patients affected by chronic myeloid leukemia who also suffer from Brugada syndrome.