Investigations of FLT3 internal tandem duplications in patients with acute myeloid leukaemia.

In acute myeloid leukaemia (AML), further prognostic determinants are required in addition to cytogenetics to predict patients at increased risk of relapse. Recent studies have indicated an internal tandem duplication (ITD) in the FLT3 gene may adversely affect clinical outcome. The studies reported in this thesis evaluated the impact of a FLT3/ITD on outcome in 854 patients treated in UK MRC AML trials. A FLT3/ITD was present in 27% patients and was associated with leucocytosis and a high percentage of bone marrow blast cells. With respect to clinical outcome it predicted for increased relapse risk (RR), adverse disease-free survival (DFS), event-free survival (EFS) and overall survival (OS). In multivariate analysis, presence of a mutation was the most significant prognostic factor predicting for RR and DFS. In order to evaluate whether FLT3 mutations can be used as markers of minimal residual disease, paired presentation and relapse samples were studied. Twenty four patients were wild type FLT3 at diagnosis and 4 acquired a FLT3 mutation at relapse. Of 20 patients positive at diagnosis, 5 who were all originally ITD+, had no detectable mutation at relapse. Furthermore, another patient had a completely different ITD at relapse which could not be detected in the presentation sample. These results suggest that, at least in some patients, FLT3 mutations are secondary events in leukaemogenesis, are unstable and thus should be used cautiously for the detection of minimal residual disease. Given the high frequency of activating FLT3 mutations in patients with AML, FLT3 and its downstream pathway are attractive targets for directed inhibition. Several promising tyrosine kinase inhibitors have recently been identified and in vitro data reported here suggest that FLT3 inhibitors may have a role either as monotherapy or in combination with conventional cytotoxic agents in the treatment of AML

Studies of FLT3 mutations in paired presentation and relapse samples from patients with acute myeloid leukemia: implications for the role of FLT3 mutations in leukemogenesis, minimal residual disease detection, and possible therapy with FLT3 inhibitors

FLT3 mutations, either internal tandem duplications (ITDs) or aspartate residue 835 (D835) point mutations, are present in approximately one third of patients with acute myeloid leukemia (AML) and have been associated with an increased relapse rate. We have studied FLT3 mutations in paired presentation and relapse samples to ascertain the biology of these mutations and to evaluate whether they can be used as markers of minimal residual disease. At diagnosis, 24 patients were wild-type FLT3, and 4 acquired a FLT3 mutation at relapse (2 D835+, 2 ITD+), with a further patient acquiring an ITD at second relapse. Of 20 patients positive at diagnosis (18 ITD+, 2 D835+), 5 who were all originally ITD+ had no detectable mutation at relapse, as determined by a sensitive radioactive polymerase chain reaction. One of these patients had acquired an N-Ras mutation not detectable at presentation. Furthermore, another patient had a completely different ITD at relapse, which could not be detected in the presentation sample. These results indicate that FLT3 mutations are secondary events in leukemogenesis, are unstable, and thus should be used cautiously for the detection of minimal residual disease

Acute Myeloid Leukemia: Focus on Novel Therapeutic Strategies

Acute myeloid leukemia (AML) is a heterogeneous disease with variable clinical outcomes. Cytogenetic analysis reveals which patients may have favorable risk disease, but 5-year survival in this category is only approximately 60%, with intermediate and poor risk groups faring far worse. Advances in our understanding of the biology of leukemia pathogenesis and prognosis have not been matched with clinical improvements. Unsatisfactory outcomes persist for the majority of patients with AML, particularly the elderly. Novel agents and treatment approaches are needed in the induction, post-remission and relapsed settings. The additions of clofarabine for relapsed or refractory disease and the hypomethylating agents represent recent advances. Clinical trials of FLT3 inhibitors have yielded disappointing results to date, with ongoing collaborations attempting to identify the optimal role for these agents. Potential leukemia stem cell targeted therapies and treatments in the setting of minimal residual disease are also under investigation. In this review, we will discuss recent advances in AML treatment and novel therapeutic strategies

The role of allogeneic haematopoietic progenitor cell transplantation in patients with diffuse large B-cell non-Hodgkin lymphomas (DLBCL)

Despite the undoubted improvement in the prognosis of patients with diffuse large B-cell lymphomas (DLBCLs) with the addition of rituximab in the front-line treatment, a significant proportion of patients still relapse. Salvage immune-chemotherapy followed by high-dose therapy with autologous haematopoietic cell transplantation (auto-HCT) remains the treatment of choice for such patients, especially in those who demonstrate chemosensitive disease. In recent years, allogeneic haematopoietic cell transplantation (allo-HCT) has increasingly been used for patients who are resistant to salvage treatment or relapse after an auto-HCT. Strategies using reduced intensity conditioning regimens have allowed application of this approach to a broader range of patients. PFS is up to 55% with a risk of relapse up to 80% depending on different studies. In multivariate analysis, several factors have been associated with favourable outcome including chemosensitivity of the disease, younger age and Karnofsky performance status at the time of the transplant being the strongest ones. DLIs have shown to induce durable responses in relapsed or progressed disease; however, its role remains controversial as the results are inferior to the responses seen in other haematological malignancies. More recently, the addition of MoAbs in the non-myeloablative conditioning regimens has shown encouraging results. In conclusion, allo-HCT is a feasible option in selective patients with chemosensitive DBCL, as it reduces the risk of relapse; however, this is achieved at the cost of significant non-relapse mortality. © 2013 Macmillan Publishers Limited All rights reserved

Dual glutathione-S-transferase-θ1 and -μ1 gene deletions determine imatinib failure in chronic myeloid leukemia

Approximately 40% of patients with chronic myeloid leukemia (CML) receiving imatinib fail treatment. There is an increased risk of CML in subjects with (i) deletions of genes encoding glutathione-S-transferase (GST)-θ1 (GSTT1) and -μ1, (GSTM1) and (ii) the GST-π1 (GSTP1) single-nucleotide polymorphism (SNP) Ile105Val (GSTP1*B; rs1695); however, their effects on imatinib treatment outcome are not known. Here, we assess the role of these GSTs in relation to imatinib treatment outcome in 193 CML patients. Deletion of GSTT1 alone, or in combination with deletion of the GSTM1 gene, significantly increased the likelihood of imatinib failure (P = 0.021 and P < 0.001, respectively). The GSTP1*B SNP was not associated with time to imatinib failure. Losses of the GSTT1 and GSTM1 genes are therefore important determinants of imatinib failure in CML. Screening for GSTT1 and GSTM1 gene deletions during diagnosis may identify patients who may be better treated using an alternative therapy

RAS mutation in acute myeloid leukemia is associated with distinct cytogenetic subgroups but does not influence outcome in patients younger than 60 years

The pathogenesis of acute myeloid leukemia (AML) involves the cooperation of mutations promoting proliferation/survival and those impairing differentiation. The RAS pathway has been implicated as a key component of the proliferative drive in AML. We have screened AML patients, predominantly younger than 60 years and treated within 2 clinical trials, for NRAS (n = 1106), KRAS (n = 739), and HRAS (n = 200) hot-spot mutations using denaturing high-performance liquid chromatography or restriction fragment length polymorphism (RFLP) analysis. NRAS mutations were confirmed in 11% of patients (126/1106) and KRAS mutations in 5% (39/739). No HRAS mutations were detected in 200 randomly selected samples. Codons most frequently mutated were N12 (43%), N13 (21%), and K12 (21%). KRAS mutations were relatively overrepresented in French-American-British (FAB) type M4 (P < .001). NRAS mutation was over-represented in the t(3;5)(q2125;q31q35) subgroup (P < .001) and underrepresented in t(15;17)(q22;q21) (P < .001). KRAS mutation was overrepresented in inv(16)(p13q22) (P = .004). Twenty-three percent of KRAS mutations were within the inv(16) subgroup. RAS mutation and FLT3 ITD were rarely coexistent (14/768; P < .001). Median percentage of RAS mutant allele assayed by quantitative RFLP analysis was 28% (N12), 19% (N13), 25% (N61), and 21% (K12). RAS mutation did not influence clinical outcome (overall/disease-free survival, complete remission, relapse rate) either for the entire cohort or within cytogenetic risk groups

Survival and freedom from progression in autotransplant lymphoma patients is independent of stem cell source: Further follow-up from the original randomised study to assess engraftment

Peripheral blood progenitor cells (PBPCs) have become the stem cell source of choice in autologous transplantation. In a prospective randomised trial, we previously demonstrated that autologous transplantation using filgrastim-mobilised PBPCs resulted in faster haematopoietic recovery with shorter hospitalisation and reduced platelet transfusions compared to bone marrow transplant (BMT). This study is a follow-up analysis evaluating the long-term clinical outcome. Seventy-two patients with advanced Hodgkin's disease or high-grade lymphoma were randomised to receive either filgrastim-mobilised PBPCs (n = 37) or bone marrow (n = 35) after BEAM chemotherapy. Fourteen patients withdrew from the study before commencing high-dose chemotherapy. Fourteen of the 58 patients who received treatment with chemotherapy and transplant have died, 6 (19%) in the ABMT arm and 8 (30%) in the PBPC transplant (PBPCT) arm. Twenty-five patients (81%) in the ABMT arm and 17 (63%) in the PBPCT arm, who received treatment, were in complete remission at the date of last follow-up. Progression-free survival and overall survival (OS) were similar for both arms (OS 81% at 46 months for ABMT versus 63% for PBPC; p = 0.38). Further prospective studies with larger number of patients need to be done to assess which source of stem cells may translate into a long-term clinical benefit for the patient