Monitoring BCR-ABL1 transcript levels in patients with Philadelphia chromosome-positive acute lymphoblastic leukemia (Ph+ ALL) is a widely adopted method to assess response to therapy. However, a ...small minority of Ph+ ALL patients express variant BCR-ABL1 transcript types, usually due to splicing of alternative BCR or ABL1 exons. Whether patients expressing these rare, variant BCR-ABL1 transcripts have a distinct phenotype or response to therapy is not known due to the limited number of reported cases. Here, we report the presenting features of Ph+ ALL in a young adult with a variant e13a3 BCR-ABL1 fusion. Molecular monitoring reflected the disease response from diagnosis through allogeneic stem cell transplantation which resulted in undetectable e13a3 BCR-ABL1 transcripts. This case highlights the value of molecular monitoring in Ph+ ALL patients with variant BCR-ABL1 transcripts and the requirement for standardization of such assays.
The introduction of the tyrosine kinase inhibitor (TKI) imatinib has revolutionised the outlook of chronic myeloid leukemia (CML); however, a significant proportion of patients develop resistance ...through several mechanisms, of which acquisition of ABL1 kinase domain mutations is prevalent. In chronic-phase patients, these mutations become evident early in the disease course. A case is described of a chronic-phase CML patient who achieved a sustained, deep molecular response but who developed an Y253H ABL1 kinase domain mutation nearly nine years after commencing imatinib. Switching therapy to bosutinib resulted in a rapid reachievement of a major molecular response. Long-term TKI treatment impacts on quality of life and late losses of responses are usually due to lack of adherence. This case highlights the requirement for ABL1 kinase domain mutation analysis in those CML patients on long-term imatinib who lost their molecular response, regardless of whether nonadherence is suspected.
A minority of chronic myeloid leukemia patients (CML) express a variety of atypical BCR-ABL1 fusion variants and, of these, the e6a2 BCR-ABL1 fusion is generally associated with an aggressive disease ...course. Progression of CML to blast crisis is associated with acquisition of additional somatic mutations yet these events have not been elucidated in patients with the e6a2 BCR-ABL1 genotype. Moreover, molecular monitoring is only sporadically performed in CML patients with atypical BCR-ABL1 fusion transcripts due to lack of consensus approaches or standardization. A case of CML is described in which comprehensive molecular analysis, including targeted next-generation sequencing, revealed a single ASXL1 mutation cooperating with an e6a2 BCR-ABL1 fusion transcript at blast crisis. A quantitative molecular monitoring approach was devised and adopted that reflected the disease response from initial treatment through allogeneic stem cell transplantation which resulted in undetectable e6a2 BCR-ABL1 transcripts. This case emphasizes the requirement for molecular monitoring in CML patients with atypical BCR-ABL1 fusion transcripts and emphasizes that comprehensive sequencing has the potential to identify targets for novel therapies in CML patients with advanced disease.
Abstract Molecular monitoring of BCR–ABL1 transcript levels using quantitative polymerase chain reaction is an essential part of the modern management of chronic myeloid leukemia patients treated ...with tyrosine kinase inhibitors. Establishing the diagnostic BCR–ABL1 fusion transcript is necessary in order to select appropriate primers and probes for such monitoring. A case is described in which quantitative polymerase chain reaction failed to detect the presence of BCR–ABL1 fusion transcript in a Philadelphia chromosome-positive chronic myeloid leukemia patient. Further investigation demonstrated a novel in-frame BCR–ABL1 fusion transcript with a breakpoint in BCR exon 13 and insertion of a sequence of ABL1 intron 1, therefore enabling subsequent molecular monitoring. This case highlights the requirement for characterization of the BCR–ABL1 transcript type at chronic myeloid leukemia diagnosis. Issues concerning standardized methodological approaches and interpretation of transcript levels in such rare cases are discussed.
Summary
In this single centre study of childhood acute lymphoblastic leukaemia (ALL) patients treated on the Medical Research Council UKALL 97/99 protocols, it was determined that minimal residual ...disease (MRD) detected by real time quantitative polymerase chain reaction (RQ‐PCR) and 3‐colour flow cytometry (FC) displayed high levels of qualitative concordance when evaluated at multiple time‐points during treatment (93·38%), and a combined use of both approaches allowed a multi time‐point evaluation of MRD kinetics for 90% (53/59) of the initial cohort. At diagnosis, MRD markers with sensitivity of at least 0·01% were identified by RQ‐PCR detection of fusion gene transcripts, IGH/TRG rearrangements, and FC. Using a combined RQ‐PCR and FC approach, the evaluation of 367 follow‐up BM samples revealed that the detection of MRD >1% at Day 15 (P = 0·04), >0·01% at the end of induction (P = 0·02), >0·01% at the end of consolidation (P = 0·01), >0·01% prior to the first delayed intensification (P = 0·01), and >0·1% prior to the second delayed intensification and continued maintenance (P = 0·001) were all associated with relapse and, based on early time‐points (end of induction and consolidation) a significant log‐rank trend (P = 0·0091) was noted between survival curves for patients stratified into high, intermediate and low‐risk MRD groups.
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