Letizia Foroni

Six-year follow-up of patients receiving imatinib for the first-line treatment of chronic myeloid leukemia

Imatinib mesylate is considered standard of care for first-line treatment of chronic phase chronic myeloid leukemia (CML-CP). In the phase III, randomized, open-label International Randomized Study of Interferon vs STI571 (IRIS) trial, previously untreated CML-CP patients were randomized to imatinib (n=553) or interferon-α (IFN) plus cytarabine (n=553). This 6-year update focuses on patients randomized to receive imatinib as first-line therapy for newly diagnosed CML-CP. During the sixth year of study treatment, there were no reports of disease progression to accelerated phase (AP) or blast crisis (BC). The toxicity profile was unchanged. The cumulative best complete cytogenetic response (CCyR) rate was 82%; 63% of all patients randomized to receive imatinib and still on study treatment showed CCyR at last assessment. The estimated event-free survival at 6 years was 83%, and the estimated rate of freedom from progression to AP and BC was 93%. The estimated overall survival was 88%––or 95% when only CML-related deaths were considered. This 6-year update of IRIS underscores the efficacy and safety of imatinib as first-line therapy for patients with CML.

Adherence Is the Critical Factor for Achieving Molecular Responses in Patients With Chronic Myeloid Leukemia Who Achieve Complete Cytogenetic Responses on Imatinib

PURPOSE There is a considerable variability in the level of molecular responses achieved with imatinib therapy in patients with chronic myeloid leukemia (CML). These differences could result from variable therapy adherence. METHODS Eighty-seven patients with chronic-phase CML treated with imatinib 400 mg/d for a median of 59.7 months (range, 25 to 104 months) who had achieved complete cytogenetic response had adherence monitored during a 3-month period by using a microelectronic monitoring device. Adherence was correlated with levels of molecular response. Other factors that could influence outcome were also analyzed. RESULTS Median adherence rate was 98% (range, 24% to 104%). Twenty-three patients (26.4%) had adherence <or= 90%; in 12 of these patients (14%), adherence was <or= 80%. There was a strong correlation between adherence rate (<or= 90% or > 90%) and the 6-year probability of a 3-log reduction (also known as major molecular response [MMR]) in BCR-ABL1 transcripts (28.4% v 94.5%; P < .001) and also complete molecular response (CMR; 0% v 43.8%; P = .002). Multivariate analysis identified adherence (relative risk [RR], 11.7; P = .001) and expression of the molecular human organic cation transporter-1 (RR, 1.79; P = .038) as the only independent predictors for MMR. Adherence was the only independent predictor for CMR. No molecular responses were observed when adherence was <or= 80% (P < .001). Patients whose imatinib doses were increased had poor adherence (86.4%). In this latter population, adherence was the only independent predictor for inability to achieve an MMR (RR, 17.66; P = .006). CONCLUSION In patients with CML treated with imatinib for some years, poor adherence may be the predominant reason for inability to obtain adequate molecular responses.

Analysis of minimal residual disease by Ig/TCR gene rearrangements: guidelines for interpretation of real-time quantitative PCR data.

Most modern treatment protocols for acute lymphoblastic leukaemia (ALL) include the analysis of minimal residual disease (MRD). To ensure comparable MRD results between different MRD-polymerase chain reaction (PCR) laboratories, standardization and quality control are essential. The European Study Group on MRD detection in ALL (ESG-MRD-ALL), consisting of 30 MRD-PCR laboratories worldwide, has developed guidelines for the interpretation of real-time quantitative PCR-based MRD data. The application of these guidelines ensures identical interpretation of MRD data between different laboratories of the same MRD-based clinical protocol. Furthermore, the ESG-MRD-ALL guidelines will facilitate the comparison of MRD data obtained in different treatment protocols, including those with new drugs.

Long-term prognostic significance of early molecular response to imatinib in newly diagnosed chronic myeloid leukemia: an analysis from the International Randomized Study of Interferon and STI571 (IRIS)

This study examines the prognostic significance of early molecular response using an expanded dataset in chronic myeloid leukemia patients enrolled in the International Randomized Study of Interferon and STI571 (IRIS). Serial molecular studies demonstrate decreases in BCR-ABL transcripts over time. Analyses of event-free survival (EFS) and time to progression to accelerated phase/blast crisis (AP/BC) at 7 years were based on molecular responses using the international scale (IS) at 6-, 12-, and 18-month landmarks. Patients with BCR-ABL transcripts > 10% at 6 months and > 1% at 12 months had inferior EFS and higher rate of progression to AP/BC compared with all other molecular response groups. Conversely, patients who achieved major molecular response [MMR: BCR-ABL (IS) ≤ 0.1%] by 18 months enjoyed remarkably durable responses, with no progression to AP/BC and 95% EFS at 7 years. The probability of loss of complete cytogenetic response by 7 years was only 3% for patients in MMR at 18 months versus 26% for patients with complete cytogenetic response but not MMR (P < .001). This study shows a strong association between the degree to which BCR-ABL transcript numbers are reduced by therapy and long-term clinical outcome, supporting the use of time-dependent molecular measures to determine optimal response to therapy. This study is registered at www.clinicaltrials.gov as NCT00006343.

Chromosomally unstable mouse tumours have genomic alterations similar to diverse human cancers

Highly rearranged and mutated cancer genomes present major challenges in the identification of pathogenetic events driving the neoplastic transformation process. Here we engineered lymphoma-prone mice with chromosomal instability to assess the usefulness of mouse models in cancer gene discovery and the extent of cross-species overlap in cancer-associated copy number aberrations. Along with targeted re-sequencing, our comparative oncogenomic studies identified FBXW7 and PTEN to be commonly deleted both in murine lymphomas and in human T-cell acute lymphoblastic leukaemia/lymphoma (T-ALL). The murine cancers acquire widespread recurrent amplifications and deletions targeting loci syntenic to those not only in human T-ALL but also in diverse human haematopoietic, mesenchymal and epithelial tumours. These results indicate that murine and human tumours experience common biological processes driven by orthologous genetic events in their malignant evolution. The highly concordant nature of genomic events encourages the use of genomically unstable murine cancer models in the discovery of biological driver events in the human oncogenome.

Assessment of BCR-ABL1 Transcript Levels at 3 Months Is the Only Requirement for Predicting Outcome for Patients With Chronic Myeloid Leukemia Treated With Tyrosine Kinase Inhibitors

PURPOSE We studied BCR-ABL1 transcript levels in patients with chronic myeloid leukemia in chronic phase (CML-CP) at 3, 6, and 12 months after starting imatinib to identify molecular milestones that would predict for overall survival (OS) and other outcomes more reliably than serial marrow cytogenetics. PATIENTS AND METHODS We analyzed 282 patients with CML-CP who received imatinib 400 mg/d as first-line therapy followed by dasatinib or nilotinib if treatment with imatinib failed. We used a receiver operating characteristic curve to identify the cutoffs in transcript levels at 3, 6, and 12 months that would best predict patient outcome. We validated our findings in an independent cohort of 95 patients treated elsewhere. RESULTS Patients with transcript levels of more than 9.84% (n = 68) at 3 months had significantly lower 8-year probabilities of OS (56.9% v 93.3%; P < .001), progression-free survival, cumulative incidence of complete cytogenetic response, and complete molecular response than those with higher transcript levels. Similarly, transcript levels of more than 1.67% (n = 87) at 6 months and more than 0.53% (n = 93) at 12 months identified high-risk patients. However, transcript levels at 3 months were the most strongly predictive for the various outcomes. When we compared OS for the groups defined molecularly at 6 and 12 months with the usual cytogenetic milestones, categorization by transcript numbers was the only independent predictor for OS (relative risk, 0.207; P < .001 and relative risk, 0.158; P < .001, respectively). CONCLUSION A single measurement of BCR-ABL1 transcripts performed at 3 months is the best way to identify patients destined to fare poorly, thereby allowing early clinical intervention.

Human bone marrow stromal cells prevent apoptosis and support the survival of chronic lymphocytic leukaemia cells in vitro

Leukaemic cells from most cases of B‐chronic lymphocytic leukaemia die rapidly by apoptosis in vitro unless they are cultured in the presence of interleukin‐4 or interferon α or γ. We now report prolonged survival of purified CLL cells cultured on bone marrow (BM) derived stromal cells in the absence of exogenous growth factors. In 10 cases of CLL examined 0–61% (mean 14.7%) of the cells were viable after 10 d culture in medium alone, whereas in the presence of BM stromal cells 10–102% (mean 47.0%) of cells were recovered alive (P < 0.005) in 7/10 cases of CLL, cells remained viable after 30 d of culture in BM stromal cells with cell recovery of 12–65%. These long‐term cultured CLL cells were Epstein Barr virus negative, shown by the failure to detect the ENBA‐2 and BZLF1 genes of EBV by PCR analysis. Identity between day 0 and day 30 CLL cells was demonstrated by sequence analysis of their clonal IgH CDR3 region. Adherence of CLL cells to BM stromal cell layers was critical for their protection from apoptosis. Separation of CLL cells from stroma by 0.45 μm culture filters resulted in loss of the protective effect of the stromal cells. Stromal cells were also able to protect CLL cells from hydrocortisone‐induced apoptotic cell death. Our findings provide an in vitro system that can be used to analyse the growth requirements of CLL cells and their chemosensitivity in an in vitro environment that mimics the in vivo milieu.

Regulation of myeloid leukaemia by the cell-fate determinant Musashi

Chronic myelogenous leukaemia (CML) can progress from a slow growing chronic phase to an aggressive blast crisis phase, but the molecular basis of this transition remains poorly understood. Here we have used mouse models of CML to show that disease progression is regulated by the Musashi–Numb signalling axis. Specifically, we find that the chronic phase is marked by high levels of Numb expression whereas the blast crisis phase has low levels of Numb expression, and that ectopic expression of Numb promotes differentiation and impairs advanced-phase disease in vivo. As a possible explanation for the decreased levels of Numb in the blast crisis phase, we show that NUP98–HOXA9, an oncogene associated with blast crisis CML, can trigger expression of the RNA-binding protein Musashi2 (Msi2), which in turn represses Numb. Notably, loss of Msi2 restores Numb expression and significantly impairs the development and propagation of blast crisis CML in vitro and in vivo. Finally we show that Msi2 expression is not only highly upregulated during human CML progression but is also an early indicator of poorer prognosis. These data show that the Musashi–Numb pathway can control the differentiation of CML cells, and raise the possibility that targeting this pathway may provide a new strategy for the therapy of aggressive leukaemias.

Poor adherence is the main reason for loss of CCyR and imatinib failure for chronic myeloid leukemia patients on long-term therapy.

We studied the relation between adherence to imatinib measured with microelectronic monitoring systems and the probabilities of losing a complete cytogenetic response (CCyR) and of imatinib failure in 87 CCyR chronic myeloid leukemia patients receiving long-term therapy. We included in our analysis the most relevant prognostic factors described to date. On multivariate analysis, the adherence rate and having failed to achieve a major molecular response were the only independent predictors for loss of CCyR and discontinuation of imatinib therapy. The 23 patients with an adherence rate less than or equal to 85% had a higher probability of losing their CCyR at 2 years (26.8% vs 1.5%, P = .0002) and a lower probability of remaining on imatinib (64.5% vs 90.6%, P = .006) than the 64 patients with an adherence rate more than 85%. In summary, we have shown that poor adherence is the principal factor contributing to the loss of cytogenetic responses and treatment failure in patients on long-term therapy.

Prospective outcome data on 267 unselected adult patients with Philadelphia chromosome–positive acute lymphoblastic leukemia confirms superiority of allogeneic transplantation over chemotherapy in the pre-imatinib era: results from the International ALL Trial MRC UKALLXII/ECOG2993

Prospective data on the value of allogeneic hematopoietic stem cell transplantation (alloHSCT) in Philadelphia chromosome-positive (Ph(+)) acute lymphoblastic leukemia (ALL) are limited. The UKALLXII/ECOG 2993 study evaluated the outcome of assigning alloHSCT with a sibling (sib) or matched unrelated donor (MUD) to patients younger than 55 years of age achieving complete remission (CR). The CR rate of 267 patients, median age 40, was 82%. Twenty-eight percent of patients proceeded to alloHSCT in first CR. Age older than 55 years or a pre-HSCT event were the most common reasons for failure to progress to alloHSCT. At 5 years, overall survival (OS) was 44% after sib alloHSCT, 36% after MUD alloHSCT, and 19% after chemotherapy. After adjustment for sex, age, and white blood count and excluding chemotherapy-treated patients who relapsed or died before the median time to alloHSCT, only relapse-free survival remained significantly superior in the alloHSCT group (odds ratio 0.31, 95% confidence interval 0.16-0.61). An intention-to-treat analysis, using the availability or not of a matched sibling donor, showed 5-year OS to be nonsignificantly better at 34% with a donor versus 25% with no donor. This prospective trial in adult Ph(+) ALL indicates a modest but significant benefit to alloHSCT. This trial has been registered with clinicaltrials.gov under identifier NCT00002514 and as ISRCTN77346223.