Minimal residual disease in chronic myeloid leukaemia patients

Model-based decision rules reduce the risk of molecular relapse after cessation of tyrosine kinase inhibitor therapy in chronic myeloid leukemia

Molecular response to imatinib (IM) in chronic myeloid leukemia (CML) is associated with a biphasic but heterogeneous decline of BCR-ABL transcript levels. We analyzed this interindividual heterogeneity and provide a predictive mathematical model to prognosticate the long-term response and the individual risk of molecular relapse on treatment cessation. The parameters of the model were determined using 7-year follow-up data from a randomized clinical trial and validated by an independent dataset. Our model predicts that a subset of patients (14%) achieve complete leukemia eradication within less than 15 years and could therefore benefit from discontinuation of treatment. Furthermore, the model prognosticates that 31% of the patients will remain in deep molecular remission (MR(5.0)) after treatment cessation after a fixed period of 2 years in MR(5.0), whereas 69% are expected to relapse. As a major result, we propose a predictor that allows to assess the patient-specific risk of molecular relapse on treatment discontinuation and to identify patients for whom cessation of therapy would be an appropriate option. Application of the suggested rule for deciding about the time point of treatment cessation is predicted to result in a significant reduction in rate of molecular relapse.

Molecular monitoring of response to imatinib (Glivec) in chronic myeloid leukemia patients: experience at a tertiary care hospital in Saudi Arabia

AIM

The aim of this study was to evaluate the response and resistance of cases to chronic myeloid leukemia (CML) therapy with tyrosine kinase (TK) inhibitors (imatinib mesylate) and to search for mutations in the breakpoint cluster region (BCR)-Abelson murine leukemia (ABL) kinase domain prior to and during therapy.

METHODS

Molecular response was assessed with real-time quantitative reverse transcription-polymerase chain reaction and was expressed as the ratio between BCR-ABL and ABL (k562 cell line) x 100. In addition, we searched for mutations in BCR-ABL kinase domain by amplification and direct sequencing of cDNA products of archived RNA samples.

RESULTS

There were 85 cases of CML Philadelphia-chromosome-positive patients. Major molecular response [corrected] (MMR) of 0.05% was achieved in 40 (47%) of 85 patients and 3-log reduction was achieved in 37 (44%) after 6 months of imatinib therapy. When molecular monitoring was extended to 12 months in a subset of delayed responsive cases (17 cases) who did not achieve an MMR at 6 months, significant changes in BCR-ABL/ABL ratio were noticed. Fifteen de novo CML patients were started directly on treatment and were monitored for BCR-ABL/ABL ratio for a further period of up to 24 months. Their median of BCR-ABL/ABL ratio was 18% at diagnosis, 0.3% after 6 months, 0.2% after 12 months, and 0.01% after 18 and 24 months. Four (27%) of 15 patients achieved MMR as 3-log reduction after 6 months, 6 (40%) after 12 months, 9 (60%) after 18 months, and 7 (46%) after 24 months. No mutation(s) or polymorphism(s) were detected in all tested patients at diagnosis, at 6 months following imatinib and following 12 months for patients showing delayed response.

CONCLUSION

BCR-ABL mutations are rare in early chronic phase and increases with CML disease progression. Therefore, search for other causes in resistant cases at this phase should be sought.

Influence of late treatment on how chronic myeloid leukemia responds to imatinib

INTRODUCTION

In Brazil, patients with chronic myeloid leukemia (CML) in the chronic phase were not given first-line imatinib treatment until 2008. Therefore, there was a long period of time between diagnosis and the initiation of imatinib therapy for many patients. This study aims to compare the major molecular remission (MMR) rates of early versus late imatinib therapy in chronic phase CML patients.

METHODS

Between May 2002 and November 2007, 44 patients with chronic phase CML were treated with second-line imatinib therapy at the Hematology Unit of the Ophir Loyola Hospital (Belém, Pará, Brazil). BCR-ABL transcript levels were measured at approximately six-month intervals using quantitative polymerase chain reaction.

RESULTS

The early treatment group presented a 60% probability of achieving MMR, while the probability for those patients who received late treatment was 40%. The probability of either not achieving MMR within one year of the initiation of imatinib therapy or losing MMR was higher in patients who received late treatment (79%), compared with patients who received early treatment (21%, odds ratio=5.75, P=0.012). The probability of maintaining MMR at 30 months of treatment was 80% in the early treatment group and 44% in the late treatment group (P=0.0005).

CONCLUSIONS

For CML patients in the chronic phase who were treated with second-line imatinib therapy, the probability of achieving and maintaining MMR was higher in patients who received early treatment compared with those patients for whom the time interval between diagnosis and initiation of imatinib therapy was longer than one year.

Molecular genetic analysis of haematological malignancies: I. Acute leukaemias and myeloproliferative disorders

Molecular genetic techniques are now routinely applied to haematological malignancies within a clinical laboratory setting. The detection of genetic rearrangements not only assists with diagnosis and treatment decisions, but also adds important prognostic information. In addition, genetic rearrangements associated with leukaemia can be used as molecular markers allowing the detection of low levels of residual disease. This review will concentrate on the application of molecular genetic techniques to the acute leukaemias and myeloprolferative disorders.

Molecular monitoring of BCR-ABL as a guide to clinical management in chronic myeloid leukaemia

Molecular monitoring of BCR-ABL transcript levels by real-time quantitative PCR is increasingly used to assess treatment response in patients with chronic myeloid leukaemia (CML). This has become particularly relevant in the era of imatinib therapy when residual levels of leukaemia usually fall below the level of detection by bone marrow cytogenetic analysis. Studies of imatinib-treated patients have determined that BCR-ABL levels measured early in therapy can predict subsequent response and the probability of acquired resistance. The defining of a molecular level of response that indicates a high probability of progression-free survival highlights the relevance of molecular analysis for clinical management. Small increases in the BCR-ABL level can identify patients with kinase domain mutations that lead to imatinib resistance. Therefore, these assays can be used as a screening strategy for mutation analysis. As second generation kinase inhibitors commence clinical trials, the molecular response will be a primary end-point that determines efficacy.

Monitoring of minimal residual disease in chronic myeloid leukemia

Detection and monitoring of minimal residual disease has become one of the most prevalent topics in chronic myeloid leukemia(CML) therapy. The goal of early detection of residual disease is to allow timely therapeutic intervention before overt relapse of therapy resistant disease occurs. The most powerful tool to serve this purpose is polymerase chain reaction (PCR). Major improvements in assay techniques have advanced PCR from a purely qualitative test with considerable variability of test results to a real-time quantitative assay with far more reproducible results than were possible before. At the same time, treatment of CML has changed dramatically since the introduction of imatinib. Integration of therapy and molecular assays such as PCR, in addition to a profound understanding of the pathophysiology of CML, has assumed even more importance. Quantitative PCR testing has become the standard monitoring strategy for patients undergoing stem cell transplantation. Although correlations have been established between positive test results and probability of relapse, no absolute guidelines for monitoring exist, especially for patients treated with imatinib.

Assessment of the response to imatinib in chronic myeloid leukemia patients - comparison between the FISH, multiplex and RT-PCR methods

OBJECTIVE

The objective of this study was to evaluate the kinetics of molecular response in chronic myeloid leukemia (CML) patients treated with imatinib and to compare between the fluorescent in situ hybridization (FISH), multiplex and real-time quantitative RT-PCR (RQ-PCR) methods with this respect.

METHODS

Molecular follow-up was carried out on 24 CML patients treated with imatinib. FISH analysis was performed according to the standard protocol. For RT-PCR the multiplex and RQ-PCR methods were used.

RESULTS

Sixty-three percent and 52% of the patients achieved complete remission according to FISH and multiplex RT-PCR analyses, respectively. Seventy-five percent of the patients achieved remission within the first year of treatment. In 83% of the cases the FISH and RT-PCR results were concordant. RQ-PCR analysis was carried out on 32 of the 41 samples negative by multiplex RT-PCR but only nine were negative. All samples with a BCR-ABL/ABL ratio below 2% were also negative by FISH. There was an excellent correlation between the RQ-PCR and the FISH tests.

CONCLUSIONS

Molecular remission according to FISH and multiplex RT-PCR can be achieved by imatinib within 1 yr of therapy. There is a good correlation between the FISH, multiplex and RQ-PCR results in terms of the kinetics of disappearance of the BCR-ABL transcript and the predictability of each method for the other. Although RQ-PCR is the most sensitive method for molecular follow-up, FISH and multiplex RT-PCR can be used as complementary tools, at least during the early period of treatment.

Molecular monitoring of minimal residual disease in patients with multiple myeloma

Improvement of transplantation strategies and a multitude of emerging novel therapies result in a better treatment outcome in patients with multiple myeloma (MM). This gives rise to the need for sensitive methods to detect minimal residual disease (MRD) in MM. Qualitative molecular monitoring using allele-specific oligonucleotide PCR for the immunoglobulin heavy chain (IgH) is well established to detect clonotypic cells after therapy or in stem cell harvests. Recently, real-time IgH PCR or limiting dilution based PCR assays offer the possibility to quantify the amount of residual tumour cells. In this review, different qualitative and quantitative IgH PCR techniques will be discussed as well as the current clinical role of molecular monitoring of MRD in patients with MM.

Acute promyelocytic leukemia: where does it stem from?

A fundamental issue in cancer biology is the identification of the target cell in which the causative molecular lesion arises. Acute myeloid leukemia (AML) is thought to reflect the transformation of a primitive stem cell compartment. The resultant 'cancer stem cells' comprise only a minor portion of the leukemic clone but give rise through differentiation to more committed progenitors as well as differentiated blasts that constitute the bulk of the tumor. The maintenance of the leukemic clone is dependent on the self-renewal capacity of the cancer stem cell compartment, which is revealed by its ability to re-initiate leukemia in a transplant setting. The cellular basis of acute promyelocytic leukemia (APL) is however less clear. APL has traditionally been considered to be the most differentiated form of AML and to arise from a committed myeloid progenitor. Here we review apparently conflicting evidence pertaining to the cellular origins of APL and propose that this leukemia may originate in more than one cellular compartment. This view could account for many apparent inconsistencies in the literature to date. An understanding of the nature of the target cell involved in transformation of APL has important implications for biological mechanism and for clinical treatment.

Detection of minimal residual disease in hematologic malignancies by real-time quantitative PCR: principles, approaches, and laboratory aspects

Detection of minimal residual disease (MRD) has prognostic value in many hematologic malignancies, including acute lymphoblastic leukemia, acute myeloid leukemia, chronic myeloid leukemia, non-Hodgkin's lymphoma, and multiple myeloma. Quantitative MRD data can be obtained with real-time quantitative PCR (RQ-PCR) analysis of immunoglobulin and T-cell receptor gene rearrangements, breakpoint fusion regions of chromosome aberrations, fusion-gene transcripts, aberrant genes, or aberrantly expressed genes, their application being dependent on the type of disease. RQ-PCR analysis can be performed with SYBR Green I, hydrolysis (TaqMan) probes, or hybridization (LightCycler) probes, as detection system in several RQ-PCR instruments. Dependent on the type of MRD-PCR target, different types of oligonucleotides can be used for specific detection, such as an allele-specific oligonucleotide (ASO) probe, an ASO forward primer, an ASO reverse primer, or germline probe and primers. To assess the quantity and quality of the RNA/DNA, one or more control genes must be included. Finally, the interpretation of RQ-PCR MRD data needs standardized criteria and reporting of MRD data needs international uniformity. Several European networks have now been established and common guidelines for data analysis and for reporting of MRD data are being developed. These networks also include standardization of technology as well as regular quality control rounds, both being essential for the introduction of RQ-PCR-based MRD detection in multicenter clinical treatment protocols.