Coexisting with clonal evolution and BCR-ABL mutant in CML patients treated with second-generation tyrosine kinase inhibitors predict the discrepancy of in vitro drug sensitivity

Impacto de la mutación T315I en el pronóstico de la leucemia mieloide crónica

Objetivos

Las mutaciones dominio quinasa BCR-ABL1 son una de las principales causas de resistencia a los inhibidores de la tirosina quinasa (ITK) en la leucemia mieloide crónica (LMC), siendo la mutación T315I la más resistente a tratamiento. El objetivo del presente estudio es determinar la frecuencia de T315I y su impacto en el pronóstico de la enfermedad, en términos de progresión de enfermedad y supervivencia.

Métodos

Se clasificó como pacientes sin respuesta a tratamiento a aquellos pacientes con respuesta clasificada como “en advertencia” o que no mostraron respuesta completa a tratamiento con ITK, según los criterios de LeukemiaNet (ELN). La mutación T315I se detectó mediante el sistema de mutación refractario a la amplificación por PCR (ARMS-PCR), cuyo resultado fue posteriormente validado mediante secuenciación. Se realizó un seguimiento de 96 meses para observar el impacto de la mutación en el pronóstico de estos pacientes.

Resultados

De los 102 pacientes que no respondieron a tratamiento, la mutación T315I fue detectada en el 21,6 %, con mayor preponderancia entre las mujeres. El 59 % de los pacientes portadores de la mutación presentaron un riesgo basal bajo por la escala Sokal. El 58,8 % de los portadores desarrollaron progresión de la enfermedad a la fase blástica. La supervivencia general (periodo de estudio: 96 meses) de los portadores de la T315I fue del 81,8 % de los pacientes portadores. Los pacientes que progresaron a la fase blástica presentaron mayor probabilidad de ser portadores de la mutación T315I.

Conclusiones

Una respuesta subóptima o falta de respuesta a tratamiento con ITK indica el desarrollo de resistencia debido a la presencia de la mutación T315I o de otras mutaciones. La identificación temprana de esta u otras mutaciones ayudaría a reorientar el tratamiento del paciente.

T315I - a gatekeeper point mutation and its impact on the prognosis of chronic myeloid leukemia

Objectives

BCR-ABL kinase domain mutations are an important cause of resistance to tyrosine kinase inhibitors (TKIs) in chronic myeloid leukaemia (CML) of which T315I is the most treatment-resilient. This study aimed to observe the frequency of T315I and its impact on disease prognosis in terms of progression and survival.

Methods

Patients with a response which categorized them into warning zone/or who failed to respond to their TKI treatment completely as per the European LeukemiaNet (ELN) were labeled as non-responders. They were assessed for T315I mutation using amplification refractory mutation system-polymerase chain reaction (ARMS-PCR) and validated via sequencing. Patients were then longitudinally followed for 96 months for the prognostic impact of the mutation.

Results

Of the 102 non-responders, T315I mutation was detected in 21.6 % of patients with a female preponderance. Almost 59 % of mutation-harbouring patients were labelled as low Sokal risk at baseline. The disease progression into the blastic phase was reported in 58.8 % of mutation-harbouring patients. Overall survival (study period: 96 months) was 81.8 % in patients harbouring T315I mutation. Patients in the blastic phase had significant odds of harbouring T315I mutation.

Conclusions

Sub-optimal response or failure to TKI treatment indicates the development of resistance due to the presence of T315I mutation or other mutation(s). Early identification will help redirect the patient's treatment.

BCR-ABL1 mutation development during first-line treatment with dasatinib or imatinib for chronic myeloid leukemia in chronic phase

BCR-ABL1 mutations are a common, well-characterized mechanism of resistance to imatinib as first-line treatment of chronic myeloid leukemia in chronic phase (CML-CP). Less is known about mutation development during first-line treatment with dasatinib and nilotinib, despite increased use because of higher response rates compared with imatinib. Retrospective analyses were conducted to characterize mutation development in patients with newly diagnosed CML-CP treated with dasatinib (n=259) or imatinib (n=260) in DASISION (Dasatinib versus Imatinib Study in Treatment-Naive CML-CP), with 3-year minimum follow-up. Mutation screening, including patients who discontinued treatment and patients who had a clinically relevant on-treatment event (no confirmed complete cytogenetic response (cCCyR) and no major molecular response (MMR) within 12 months; fivefold increase in BCR-ABL1 with loss of MMR; loss of CCyR), yielded a small number of patients with mutations (dasatinib, n=17; imatinib, n=18). Dasatinib patients had a narrower spectrum of mutations (4 vs 12 sites for dasatinib vs imatinib), fewer phosphate-binding loop mutations (1 vs 9 mutations), fewer multiple mutations (1 vs 6 patients) and greater occurrence of T315I (11 vs 0 patients). This trial was registered at www.clinicaltrials.gov as NCT00481247.

Imatinib mesylate resistance and mutations: An Indian experience

The treatment of chronic myeloid leukemia (CML) has been revolutionized by the small molecule selective kinase inhibitor imatinib mesylate. Imanitib was the first BCR-ABL targeted agent approved for the treatment of CML patients and confers significant response in most patients; however, a substantial number of patients are initially refractory to the drug or may develop resistance during the course of treatment. Point mutations in the kinase domain (KD) of BCR-ABL that impact drug binding have been identified as one of the major mechanisms of resistance. We present here an overview of the current practice in monitoring for such mutations, including the methods used, criteria for investigating and guidelines for reporting the mutations. We further present and discuss the experience of our own laboratory in studying the KD mutations in Indian CML patients on imatinib treatment.