Characteristics and outcome of patients with therapy-related acute promyelocytic leukemia front-line treated with or without arsenic trioxide.

Therapy-related acute promyelocytic leukemia (t-APL) is relatively rare, with limited data on outcome after treatment with arsenic trioxide (ATO) compared to standard intensive chemotherapy (CTX). We evaluated 103 adult t-APL patients undergoing treatment with all-trans retinoic acid (ATRA) alone (n=7) or in combination with ATO (n=24), CTX (n=53), or both (n=19). Complete remissions were achieved after induction therapy in 57% with ATRA, 100% with ATO/ATRA, 78% with CTX/ATRA, and 95% with CTX/ATO/ATRA. Early death rates were 43% for ATRA, 0% for ATO/ATRA, 12% for CTX/ATRA and 5% for CTX/ATO/ATRA. Three patients relapsed, two developed therapy-related acute myeloid leukemia and 13 died in remission including seven patients with recurrence of the prior malignancy. Median follow-up for survival was 3.7 years. None of the patients treated with ATRA alone survived beyond one year. Event-free survival was significantly higher after ATO-based therapy (95%, 95% CI, 82-99%) as compared to CTX/ATRA (78%, 95% CI, 64-87%; P=0.042), if deaths due to recurrence of the prior malignancy were censored. The estimated 2-year overall survival in intensively treated patients was 88% (95% CI, 80-93%) without difference according to treatment (P=0.47). ATO when added to ATRA or CTX/ATRA is feasible and leads to better outcomes as compared to CTX/ATRA in t-APL.

A comparison of clofarabine with ara-C, each in combination with daunorubicin as induction treatment in older patients with acute myeloid leukaemia.

The study was designed to compare clofarabine plus daunorubicin vs daunorubicin/ara-C in older patients with acute myeloid leukaemia (AML) or high-risk myelodysplastic syndrome (MDS). Eight hundred and six untreated patients in the UK NCRI AML16 trial with AML/high-risk MDS (median age, 67 years; range 56-84) and normal serum creatinine were randomised to two courses of induction chemotherapy with either daunorubicin/ara-C (DA) or daunorubicin/clofarabine (DClo). Patients were also included in additional randomisations; ± one dose of gemtuzumab ozogamicin in course 1; 2v3 courses and ± azacitidine maintenance. The primary end point was overall survival. The overall response rate was 69% (complete remission (CR) 60%; CRi 9%), with no difference between DA (71%) and DClo (66%). There was no difference in 30-/60-day mortality or toxicity: significantly more supportive care was required in the DA arm even though platelet and neutrophil recovery was significantly slower with DClo. There were no differences in cumulative incidence of relapse (74% vs 68%; hazard ratio (HR) 0.93 (0.77-1.14), P=0.5); survival from relapse (7% vs 9%; HR 0.96 (0.77-1.19), P=0.7); relapse-free (31% vs 32%; HR 1.02 (0.83-1.24), P=0.9) or overall survival (23% vs 22%; HR 1.08 (0.93-1.26), P=0.3). Clofarabine 20 mg/m2 given for 5 days with daunorubicin is not superior to ara-C+daunorubicin as induction for older patients with AML/high-risk MDS.

Expression of CD33 is a predictive factor for effect of gemtuzumab ozogamicin at different doses in adult acute myeloid leukaemia.

It remains unclear in adult acute myeloid leukaemia (AML) whether leukaemic expression of CD33, the target antigen for gemtuzumab ozogamicin (GO), adds prognostic information on GO effectiveness at different doses. CD33 expression quantified in 1583 patients recruited to UK-NCRI-AML17 (younger adults) and UK-NCRI-AML16 (older adults) trials was correlated with clinical outcomes and benefit from GO including a dose randomisation. CD33 expression associated with genetic subgroups, including lower levels in both adverse karyotype and core-binding factor (CBF)-AML, but was not independently prognostic. When comparing GO versus no GO (n=393, CBF-AMLs excluded) by stratified subgroup-adjusted analysis, patients with lowest quartile (Q1) %CD33-positivity had no benefit from GO (relapse risk, HR 2.41 (1.27-4.56), P=0.009 for trend; overall survival, HR 1.52 (0.92-2.52)). However, from the dose randomisation (NCRI-AML17, n=464, CBF-AMLs included), 6 mg/m2 GO only had a relapse benefit without increased early mortality in CD33-low (Q1) patients (relapse risk HR 0.64 (0.36-1.12) versus 1.70 (0.99-2.92) for CD33-high, P=0.007 for trend). Thus CD33 expression is a predictive factor for GO effect in adult AML; although GO does not appear to benefit the non-CBF AML patients with lowest CD33 expression a higher GO dose may be more effective for CD33-low but not CD33-high younger adults.

The HSP90 inhibitor ganetespib: A potential effective agent for Acute Myeloid Leukemia in combination with cytarabine.

HSP90 is a multi-client chaperone involved in regulating a large array of cellular processes and is commonly overexpressed in many different cancer types including hematological malignancies. Inhibition of HSP90 holds promise for targeting multiple molecular abnormalities and is therefore an attractive target for heterogeneous malignancies such as Acute Myeloid Leukemia (AML). Ganetespib is a highly potent second generation HSP90 inhibitor which we show is significantly more effective against primary AML blasts at nanomolar concentrations when compared with cytarabine (p<0.001). Dose dependant cytotoxicity was observed with an apoptotic response coordinate with the loss of pro-survival signaling through the client protein AKT. Combination treatment of primary blasts with ganetespib and cytarabine showed good synergistic interaction (combination index (CI): 0.47) across a range of drug effects with associated reduction in HSP70 feedback and AKT signaling levels. In summary, we show ganetespib to have high activity in primary AMLs as a monotherapy and a synergistic relationship with cytarabine when combined. The combination of cytotoxic cell death, suppression of cytoprotective/drug resistance mechanisms such as AKT and reduced clinical toxicity compared to other HSP90 inhibitors provide strong rationale for the clinical assessment of ganetespib in AML.

A randomised comparison of the novel nucleoside analogue sapacitabine with low-dose cytarabine in older patients with acute myeloid leukaemia.

The development of new treatments for older patients with acute myeloid leukaemia (AML) is an active area, but has met with limited success. Sapacitabine is a novel orally administered nucleoside analogue that has shown encouraging activity in unrandomised early-stage trials. We randomised 143 untreated patients with AML or with high-risk myelodysplastic syndrome (>10% marrow blasts) between sapacitibine and low-dose ara-C (LDAC) in our 'Pick a Winner' trial design. At the planned interim analysis there was no difference between LDAC and sapacitibine in terms of remission rate (CR/CRi, 27% vs 16% hazard ratio (HR) 1.98(0.90-4.39) P=0.09), relapse-free survival (10% vs 14% at 2 years, HR 0.73(0.33-1.61) P=0.4) or overall survival (OS; 12% vs 11% at 2 years, HR 1.24(0.86-1.78) P=0.2). Sapacitibine was well tolerated, apart from more grade 3/4 diarrhoea. On the basis of these findings sapacitibine did not show sufficient evidence of benefit over LDAC for the trial to be continued.

A comparative assessment of the curative potential of reduced intensity allografts in acute myeloid leukaemia.

Allogeneic stem cell transplantation (SCT) provides the best mechanism of preventing relapse in acute myeloid leukaemia (AML). However non-relapse mortality (NRM) negates this benefit in older patients. Reduced intensity conditioning (RIC) permits SCT with reduced NRM, but its contribution to cure is uncertain. In the MRC AML15 Trial, patients in remission without favourable risk disease could receive SCT from a matched sibling or unrelated donor (MUD). If aged >45 years, a RIC was recommended and in patients aged 35-44 years, either RIC or myeloablative conditioning was permitted. The aim was to determine which approach improved survival and within which prespecified cytogenetic groups. RIC transplants significantly reduced relapse (adjusted hazard ratio (HR) 0.66 (0.50-0.85), P=0.002) compared to chemotherapy The 5-year overall survival from a sibling RIC (61%) was superior to a MUD RIC (37%; adjusted HR 1.50 (1.01-2.21), P=0.04) due to lower NRM (34 vs 14%, P=0.002) In adjusted analyses, there was a survival benefit for sibling RIC over chemotherapy (59 vs 49%, HR 0.75 (0.57-0.97), P=0.03), with consistent results in intermediate and adverse-risk patients. In patients aged 35-44 years, best outcomes were seen with a sibling RIC transplant, although a comparison with chemotherapy and myeloablative transplant was not significant in adjusted analyses (P=0.3).

Resistance prediction in AML: analysis of 4601 patients from MRC/NCRI, HOVON/SAKK, SWOG and MD Anderson Cancer Center.

Therapeutic resistance remains the principal problem in acute myeloid leukemia (AML). We used area under receiver-operating characteristic curves (AUCs) to quantify our ability to predict therapeutic resistance in individual patients, where AUC=1.0 denotes perfect prediction and AUC=0.5 denotes a coin flip, using data from 4601 patients with newly diagnosed AML given induction therapy with 3+7 or more intense standard regimens in UK Medical Research Council/National Cancer Research Institute, Dutch-Belgian Cooperative Trial Group for Hematology/Oncology/Swiss Group for Clinical Cancer Research, US cooperative group SWOG and MD Anderson Cancer Center studies. Age, performance status, white blood cell count, secondary disease, cytogenetic risk and FLT3-ITD/NPM1 mutation status were each independently associated with failure to achieve complete remission despite no early death ('primary refractoriness'). However, the AUC of a bootstrap-corrected multivariable model predicting this outcome was only 0.78, indicating only fair predictive ability. Removal of FLT3-ITD and NPM1 information only slightly decreased the AUC (0.76). Prediction of resistance, defined as primary refractoriness or short relapse-free survival, was even more difficult. Our limited ability to forecast resistance based on routinely available pretreatment covariates provides a rationale for continued randomization between standard and new therapies and supports further examination of genetic and posttreatment data to optimize resistance prediction in AML.

The prognostic relevance of flt3 and npm1 mutations on older patients treated intensively or non-intensively: a study of 1312 patients in the UK NCRI AML16 trial.

Although the prognostic impact of mutations of FLT3 and NPM1 have been extensively studied in younger patients with acute myeloid leukaemia, less is known in older patients whether treated intensively or non-intensively, or in the context of existing prognostic scores. In 1312 patients 16 and 21%, respectively had an FLT3 and NPM1 mutation. An FLT3 mutation did not affect remission rate in intensively or non-intensively treated patients but was associated with an inferior survival. All patients with an NPM1c mutation had a significantly higher remission rate irrespective of treatment approach but survival was not improved, overall, or in any genotype except as in younger patients, in the FLT3 WT NPM1c mutant subgroup. When incorporated into an established multi-parameter prognostic risk score, the molecular information provided additional prognostic definition in 11% of patients.

Hyperdiploidy with 49-65 chromosomes represents a heterogeneous cytogenetic subgroup of acute myeloid leukemia with differential outcome.

Chromosome gain is frequent in acute myeloid leukemia (AML) and is counted alongside structural abnormalities when determining karyotype complexity. However, there are few studies investigating the cytogenetic profile and outcome of patients with a hyperdiploid karyotype (49-65 chromosomes, HK). We identified 221 (14%) patients with HK out of 1563 patients with three or more chromosomal abnormalities. HK was not associated with sex, white cell count and secondary disease status, but was more prevalent among children (22% vs 13%). The pattern of chromosomal gain and loss was non-random and chromosomes 8, 13 and 21 were the most frequently gained. Three distinct subgroups (numerical, structural and adverse) were identified with differential outcome: 5-year cumulative incidence of relapse of 52%, 68% and 76%, respectively (P=0.008). Patients in the adverse subgroup had poorer survival compared with patients with only numerical abnormalities (adjusted hazard ratio: 2.01 (95% confidence interval: 1.43-2.83), P=0.0002). This outcome heterogeneity was similar among children and adults. In conclusion, AML patients with a HK should not automatically be assigned to the adverse cytogenetic risk group on the basis of complexity. Instead they should be assessed for the presence of specific chromosomal abnormalities, which are known to harbour an adverse effect.

The importance of relative mutant level for evaluating impact on outcome of KIT, FLT3 and CBL mutations in core-binding factor acute myeloid leukemia.

Several different mutations collaborate with the fusion proteins in core-binding factor acute myeloid leukemia (CBF-AML) to induce leukemogenesis, but their prognostic significance remains unclear. We screened 354 predominantly younger (<60 years) adults with t(8;21) (n=199) or inv(16) (n=155) entered into UK MRC trials for KIT, FLT3 tyrosine kinase domain (FLT3(TKD)), N-RAS, K-RAS and c-CBL mutations and FLT3 internal tandem duplications (FLT3(ITD)) and assessed the impact of relative mutant level on outcome. Overall, 28% had KIT, 6% FLT3(ITD), 10% FLT3(TKD), 27% RAS and 6% CBL mutations. Mutant levels for all genes/loci were highly variable. KIT mutations were associated with a higher cumulative incidence of relapse but in multivariate analysis this was only significant for cases with a higher mutant level of 25% or greater (95% confidence interval (CI)=1.01-1.52, P=0.04). Similarly, only FLT3(ITD-HIGH) was a significant adverse factor for overall survival (OS; CI=1.27-5.39, P=0.004). Conversely, FLT3(TKD-HIGH) and CBL(HIGH) were both favorable factors for OS (CI= 0.31-0.89, P=0.01 and CI=0.05-0.85, P=0.02, respectively). KIT mutations were frequently lost at relapse, which is relevant to minimal residual disease detection and the clinical use of KIT inhibitors. These results indicate that relative mutant level should be taken into account when evaluating the impact of mutations in CBF-AML.

The addition of gemtuzumab ozogamicin to low-dose Ara-C improves remission rate but does not significantly prolong survival in older patients with acute myeloid leukaemia: results from the LRF AML14 and NCRI AML16 pick-a-winner comparison.

The treatment of older patients with acute myeloid leukaemia, who are not considered suitable for conventional intensive therapy, is unsatisfactory. Low-dose Ara-C(LDAC) has been established as superior to best supportive care, but only benefits the few patients who enter complete remission. Alternative or additional treatments are required to improve the situation. This randomised trial compared the addition of the immunoconjugate, gemtuzumab ozogamicin (GO), at a dose of 5 mg on day 1 of each course of LDAC, with the intention of improving the remission rate and consequently survival. Between June 2004 and June 2010, 495 patients entered the randomisation. The addition of GO significantly improved the remission rate (30% vs 17%; odds ratio(OR) 0.48 (0.32-0.73); P=0.006), but not the 12 month overall survival (25% vs 27%). The reason for the induction benefit failing to improve OS was two-fold: survival of patients in the LDAC arm who did not enter remission and survival after relapse were both superior in the LDAC arm. Although the addition of GO to LDAC doubled the remission rate it did not improve overall survival. Maintaining remission in older patients remains elusive.

γ-Catenin is overexpressed in acute myeloid leukemia and promotes the stabilization and nuclear localization of ß-catenin.

Canonical Wnt signaling regulates the transcription of T-cell factor (TCF)-responsive genes through the stabilization and nuclear translocation of the transcriptional co-activator, ß-catenin. Overexpression of ß-catenin features prominently in acute myeloid leukemia (AML) and has previously been associated with poor clinical outcome. Overexpression of γ-catenin mRNA (a close homologue of ß-catenin) has also been reported in AML and has been linked to the pathogenesis of this disease, however, the relative roles of these catenins in leukemia remains unclear. Here we report that overexpression and aberrant nuclear localization of γ-catenin is frequent in AML. Significantly, γ-catenin expression was associated with ß-catenin stabilization and nuclear localization. Consistent with this, we found that ectopic γ-catenin expression promoted the stabilization and nuclear translocation of ß-catenin in leukemia cells. ß-Catenin knockdown demonstrated that both γ- and ß-catenin contribute to TCF-dependent transcription in leukemia cells. These data indicate that γ-catenin expression is a significant factor in the stabilization of ß-catenin in AML. We also show that although normal cells exclude nuclear translocation of both γ- and ß-catenin, this level of regulation is lost in the majority of AML patients and cell lines, which allow nuclear accumulation of these catenins and inappropriate TCF-dependent transcription.

Inclusion of chemotherapy in addition to anthracycline in the treatment of acute promyelocytic leukaemia does not improve outcomes: results of the MRC AML15 trial.

Two hundred eighty-five patients, median age 42, with PML-RARα-positive acute promyelocytic leukaemia were randomised to Ara-C-containing 'Medical Research Council (MRC) Chemotherapy'+ATRA (All-trans-retinoic acid) or anthracycline+ATRA (modified 'Spanish') therapy. MRC treatment comprised four courses with ATRA in courses 1-2. Spanish treatment comprised four anthracycline-based courses with ATRA in courses 1-3. In course 3 patients were randomised to gemtuzumab ozogamicin (GO) or not. The Spanish arm received 24-month maintenance. Patients were sequentially molecularly monitored. Quality of life was assessed at baseline, 3, 6, 9, 12, 24 months. Remission rates were similar in both arms (93%): cumulative incidence of haematological relapse (CIHR) was 6% at 5 years; 5 patients relapsed molecularly. Survival post relapse was 80%. There were more deaths in remission in the MRC arm (4% vs 10%: P=0.2). The overall 5-year relapse-free and overall survival was similar between arms (81% vs 82% and 84% vs 83%, respectively). More supportive care and hospitalisation (81.8 vs 63 days, P<0.0001) was required in the MRC arm. GO did not provide benefit. High white blood cell count (>10 × 10(9)/l) was not prognostic overall, or within treatment arms. Both approaches deliver similar results with minor differences in quality of life. MRC treatment required more hospitalisation. This suggests that additional chemotherapy, Ara-C in particular, is not required.