title: Molecular measurement of BCR-ABL transcript variations in chronic myeloid leukemia patients in cytogenetic remission.
abstract: BACKGROUND
  The monitoring of BCR-ABL transcript levels by real-time quantitative polymerase chain reaction (RT-qPCR) has become important to assess minimal residual disease (MRD) and standard of care in the treatment of chronic myeloid leukemia (CML). In this study, we performed a prospective, sequential analysis using RT-qPCR monitoring of BCR-ABL gene rearrangements in blood samples from 91 CML patients in chronic phase (CP) who achieved complete cytogenetic remission (CCyR) and major molecular remission (MMR) throughout imatinib treatment.
  
  
  METHODS
  The absolute level of BCR-ABL transcript from peripheral blood was serially measured every 4 to 12 weeks by RT-qPCR. Only level variations > 0.5%, according to the international scale, was considered positive. Sequential cytogenetic analysis was also performed in bone marrow samples from all patients using standard protocols.
  
  
  RESULTS
  Based on sequential analysis of BCR-ABL transcripts, the 91 patients were divided into three categories: (A) 57 (62.6%) had no variation on sequential analysis; (B) 30 (32.9%) had a single positive variation result obtained in a single sample; and (C) 4 (4.39%) had variations of BCR-ABL transcripts in at least two consecutive samples. Of the 34 patients who had elevated levels of transcripts (group B and C), 19 (55.8%) had a < 1% of BCR-ABL/BCR ratio, 13 (38.2%) patients had a 1% to 10% increase and 2 patients had a >10% increase of RT-qPCR. The last two patients had lost a CCyR, and none of them showed mutations in the ABL gene. Transient cytogenetic alterations in Ph-negative cells were observed in five (5.5%) patients, and none of whom lost CCyR.
  
  
  CONCLUSIONS
  Despite an increase levels of BCR-ABL/BCR ratio variations by RT-qPCR, the majority of CML patients with MMR remained in CCyR. Thus, such single variations should neither be considered predictive of subsequent failure and nor an indication for altering imatinib dose or switching to second generation therapy. Changing of imatinib on the basis of BCR-ABL/BCR% sustained increase and mutational studies is a prudent approach for preserving other therapeutic options in imatinib-resistant patients.
authors.affiliation: Department of Hematology, Faculty of Medicine, University of São Paulo, São Paulo, Brazil. isbendit@usp.br.
authors.forename: Mariana
authors.initials: M
authors.lastname: Serpa
authors.forename: Sabri S
authors.initials: SS
authors.lastname: Sanabani
authors.forename: Pedro Enrique
authors.initials: PE
authors.lastname: Dorliac-Llacer
authors.forename: Monika
authors.initials: M
authors.lastname: Conchon
authors.forename: Thales Dalessandro Meneguin
authors.initials: TD
authors.lastname: Pereira
authors.forename: Luciana
authors.initials: L
authors.lastname: Nardinelli
authors.forename: Juliana Lima
authors.initials: JL
authors.lastname: Costa
authors.forename: Mafalda Megumi Yoshinaga
authors.initials: MM
authors.lastname: Novaes
authors.forename: Patricia de Barros
authors.initials: Pde B
authors.lastname: Ferreira
authors.forename: Israel
authors.initials: I
authors.lastname: Bendit