Chemotherapy options for previously untreated acute myeloid leukemia

INTRODUCTION

Intensive chemotherapy with cytarabine and an anthracycline for untreated acute myeloid leukemia (AML) has remained largely unchanged over the past 40 years, despite many large trials examining the choice and dosing of these agents.

AREAS COVERED

We will review the major published clinical trials for untreated AML that have established the dosing choice and schedule for intensive therapy, as well as trials for patients not eligible for more intensive therapy. We will also discuss treatment considerations for subgroups of patients.

EXPERT OPINION

While one or two cycles of anthracycline and cytarabine-based combination regimens remain the standard of care for younger and older patients with AML deemed fit to receive induction chemotherapy, controversy remains regarding the optimal selection and dosing schedule for anthracyclines. Low-intensity regimens, such as low-dose cytarabine and hypomethylating agents, can achieve a complete response even with adverse risk features, and can be used in a fit subset of older patients not eligible for clinical trial or transplant. Incorporation of new targeted agents, such as tyrosine kinase and small-molecule inhibitors, combined with better selection of drugs for unique patient cohorts, will likely be necessary to substantially improve outcomes in AML.

Selective Toxicity of Investigational Ixazomib for Human Leukemia Cells Expressing Mutant Cytoplasmic NPM1: Role of Reactive Oxygen Species

PURPOSE

This study was performed to determine whether the investigational proteasome inhibitor ixazomib demonstrated selective antineoplastic activity against acute myelogenous leukemia cells expressing a mutated nucleophosmin-1 gene and to gain a better understanding of its mechanisms of action.

EXPERIMENTAL DESIGN

The cytotoxic effects of ixazomib treatment were analyzed in human acute myelogenous leukemia (AML) cell lines and primary AML samples expressing wild-type or mutated NPM1 (NPMc(+)). The potential roles of oxidative stress in mediating cytotoxic activity were determined using flow cytometry, enzyme-based assays, and Western blots.

RESULTS

Apoptosis induced by ixazomib was abrogated by knockdown of NPM1/NPMc(+)expression using an inducible shRNA construct and enhanced by NPMc(+)overexpression. Cytotoxicity was associated with superoxide generation and was reduced by the addition of the antioxidant N-acetylcysteine. AML cells expressing NPMc(+)had significantly reduced levels of intracellular glutathione and NADPH associated with reduced antioxidant responses to drug treatment. Treatment of 3 patients with relapsed NPMc(+)AML resulted in an antileukemic effect in 1 patient as demonstrated by a marked reduction of leukemic blasts in the peripheral blood. Efficacy was associated with superoxide generation, reduced glutathione levels, and reduced mRNA and protein expression of antioxidant effectors in responding cells.

CONCLUSIONS

In this study, a direct association was observed between NPMc(+)expression in AML, reduced antioxidant responses, and enhanced sensitivity to an oral proteasome inhibitor that induces oxidative stress. These data suggest that intracellular determinants of antioxidant responses may be good predictors of therapeutic response to ixazomib.

Disparities in early death and survival in children, adolescents, and young adults with acute promyelocytic leukemia in California

BACKGROUND

Findings from clinical trials and population-based studies have differed with regard to whether mortality within 30 days of diagnosis (early death) of acute promyelocytic leukemia (APL) has decreased in the era of all-trans retinoic acid and anthracycline-based chemotherapy.

METHODS

Using data from the California Cancer Registry, the authors investigated 7-day and 30-day mortality and survival in 772 patients who were aged birth to 39 years when they were diagnosed with APL during 1988 to 2011. Logistic regression and Cox proportional models were used to examine the association of early death and survival, respectively, with sociodemographic and clinical factors.

RESULTS

The overall 30-day mortality decreased significantly over time, from 26% (1988-1995) to 14% (2004-2011) (P =.004). On multivariable analysis, the odds of 30-day mortality were 3 times as high during 1988 through 1995 than 2004 through 2011 (P =.001). However, 7-day mortality did not improve over time (P =.229). When patients who died within 7 days of diagnosis were excluded, the 30-day mortality during 1996 to 2011 was 3% to 8%, which is similar to levels reported in clinical trials. Higher early death and lower survival were associated with a lack of health insurance (1996-2011) (early death odds ratio, 2.67; P =.031) and Hispanic race/ethnicity (early death odds ratio, 2.13; P =.014). Early death was not found to be associated with age, sex, socioeconomic status, or hospital type. Black patients also experienced worse survival.

CONCLUSIONS

The findings of the current study revealed a decreased 30-day mortality during the all-trans retinoic acid era, but 7-day mortality remained high. Efforts to achieve equal outcomes in young patients with APL should focus on improving access to effective treatment, mainly among uninsured patients and those of Hispanic and black race/ethnicity.

Sequential azacitidine plus lenalidomide in previously treated elderly patients with acute myeloid leukemia and higher risk myelodysplastic syndrome

The outcome of sequential azacitidine with lenalidomide has not been reported in previously treated patients with acute myeloid leukemia (AML) and higher risk myelodysplastic syndrome (MDS). This study describes a phase 2 study evaluating the safety and efficacy of this combination in elderly patients with AML and MDS with prior hypomethylating agent (HMA) and/or immunomodulatory agent exposure. Patients were treated on a 42-day cycle with azacitidine at 75 mg/m2 SQ/IV daily on days 1-7, followed by lenalidomide 50 mg orally daily on days 8-28. The median number of treatment cycles on study was two (range = 1-11). Of 32 evaluable patients, the overall response rate was 25%. Neutropenic fever was the most common serious adverse event, but overall the combination was well-tolerated. The median overall survival (OS) for responders vs non-responders was 9.8 vs 4.0 months, respectively (HR = 0.36, p = 0.016). In conclusion, this combination demonstrated modest clinical activity in this poor risk population.

Epidemiology and Clinical Significance of Secondary and Therapy-Related Acute Myeloid Leukemia: A National Population-Based Cohort Study

PURPOSE

Secondary and therapy-related acute myeloid leukemia (sAML and tAML, respectively) remain therapeutic challenges. Still, it is unclear whether their inferior outcome compared with de novo acute myeloid leukemia (AML) varies as a result of previous hematologic disease or can be explained by differences in karyotype and/or age.

PATIENTS AND METHODS

In a Danish national population-based study of 3,055 unselected patients with AML diagnosed from 2000 to 2013, we compared the frequencies and characteristics of tAML, myelodysplastic syndrome (MDS) -sAML, and non-MDS-sAML (chronic myelomonocytic leukemia and myeloproliferative neoplasia) versus de novo AML. Limited to intensive therapy patients, we compared chance of complete remission by logistic regression analysis and used a pseudo-value approach to compare relative risk (RR) of death at 90 days, 1 year, and 3 years, overall and stratified by age and karyotype. Results were given crude and adjusted with 95% CIs.

RESULTS

Overall, frequencies of sAML and tAML were 19.8% and 6.6%, respectively. sAML, but not tAML, was associated with low likelihood of receiving intensive treatment. Among intensive therapy patients (n = 1,567), antecedent myeloid disorder or prior cytotoxic exposure was associated with decreased complete remission rates and inferior survival (3-year adjusted RR for MDS-sAML, non-MDS-sAML, and tAML: RR, 1.14; 95% CI, 1.02 to 1.32; RR, 1.27; 95% CI, 1.16 to 1.34; and RR, 1.16; 95% CI, 1.03 to 1.32, respectively) compared with de novo AML. Among patients ≥ 60 years old and patients with adverse karyotype, previous MDS or tAML did not impact overall outcomes, whereas non-MDS-sAML was associated with inferior survival across age and cytogenetic risk groups (adverse risk cytogenetics: 1-year adjusted RR, 1.47; 95% CI, 1.23 to 1.76; patients ≥ 60 years old: 1-year adjusted RR, 1.31; 95% CI, 1.06 to 1.61).

CONCLUSION

Our results support that de novo AML, sAML, and tAML are biologically and prognostically distinct subtypes of AML. Patients with non-MDS-sAML have dismal outcomes, independent of age and cytogenetics. Previous myeloid disorder, age, and cytogenetics are crucial determinants of outcomes and should be integrated in treatment recommendations for these patients.

Mass Cytometric Functional Profiling of Acute Myeloid Leukemia Defines Cell-Cycle and Immunophenotypic Properties That Correlate with Known Responses to Therapy

Acute myeloid leukemia (AML) is characterized by a high relapse rate that has been attributed to the quiescence of leukemia stem cells (LSC), which renders them resistant to chemotherapy. However, this hypothesis is largely supported by indirect evidence and fails to explain the large differences in relapse rates across AML subtypes. To address this, bone marrow aspirates from 41 AML patients and five healthy donors were analyzed by high-dimensional mass cytometry. All patients displayed immunophenotypic and intracellular signaling abnormalities within CD34(+)CD38(lo) populations, and several karyotype- and genotype-specific surface marker patterns were identified. The immunophenotypic stem and early progenitor cell populations from patients with clinically favorable core-binding factor AML demonstrated a 5-fold higher fraction of cells in S-phase compared with other AML samples. Conversely, LSCs in less clinically favorable FLT3-ITD AML exhibited dramatic reductions in S-phase fraction. Mass cytometry also allowed direct observation of the in vivo effects of cytotoxic chemotherapy.

SIGNIFICANCE

The mechanisms underlying differences in relapse rates across AML subtypes are poorly understood. This study suggests that known chemotherapy sensitivities of common AML subsets are mediated by cell-cycle differences among LSCs and provides a basis for using in vivo functional characterization of AML cells to inform therapy selection.

Pharmacological targeting of miR-155 via the NEDD8-activating enzyme inhibitor MLN4924 (Pevonedistat) in FLT3-ITD acute myeloid leukemia

High levels of microRNA-155 (miR-155) are associated with poor outcome in acute myeloid leukemia (AML). In AML, miR-155 is regulated by NF-κB, the activity of which is, in part, controlled by the NEDD8-dependent ubiquitin ligases. We demonstrate that MLN4924, an inhibitor of NEDD8-activating enzyme presently being evaluated in clinical trials, decreases binding of NF-κB to the miR-155 promoter and downregulates miR-155 in AML cells. This results in the upregulation of the miR-155 targets SHIP1, an inhibitor of the PI3K/Akt pathway, and PU.1, a transcription factor important for myeloid differentiation, leading to monocytic differentiation and apoptosis. Consistent with these results, overexpression of miR-155 diminishes MLN4924-induced antileukemic effects. In vivo, MLN4924 reduces miR-155 expression and prolongs the survival of mice engrafted with leukemic cells. Our study demonstrates the potential of miR-155 as a novel therapeutic target in AML via pharmacologic interference with NF-κB-dependent regulatory mechanisms. We show the targeting of this oncogenic microRNA with MLN4924, a compound presently being evaluated in clinical trials in AML. As high miR-155 levels have been consistently associated with aggressive clinical phenotypes, our work opens new avenues for microRNA-targeting therapeutic approaches to leukemia and cancer patients.

G-CSF priming, clofarabine, and high dose cytarabine (GCLAC) for upfront treatment of acute myeloid leukemia, advanced myelodysplastic syndrome or advanced myeloproliferative neoplasm

Prior study of the combination of clofarabine and high dose cytarabine with granulocyte colony-stimulating factor (G-CSF) priming (GCLAC) in relapsed or refractory acute myeloid leukemia resulted in a 46% rate of complete remission despite unfavorable risk cytogenetics. A multivariate analysis demonstrated that the remission rate and survival with GCLAC were superior to FLAG (fludarabine, cytarabine, G-CSF) in the relapsed setting. We therefore initiated a study of the GCLAC regimen in the upfront setting in a multicenter trial. The objectives were to evaluate the rates of complete remission (CR), overall and relapse-free survival (OS and RFS), and toxicity of GCLAC. Clofarabine was administered at 30 mg m(-2) day(-1) × 5 and cytarabine at 2 g m(-2) day(-1) × 5 after G-CSF priming in 50 newly-diagnosed patients ages 18-64 with AML or advanced myelodysplastic syndrome (MDS) or advanced myeloproliferative neoplasm (MPN). Responses were assessed in the different cytogenetic risk groups and in patients with antecedent hematologic disorder. The overall CR rate was 76% (95% confidence interval [CI] 64-88%) and the CR + CRp (CR with incomplete platelet count recovery) was 82% (95% CI 71-93%). The CR rate was 100% for patients with favorable, 84% for those with intermediate, and 62% for those with unfavorable risk cytogenetics. For patients with an antecedent hematologic disorder (AHD), the CR rate was 65%, compared to 85% for those without an AHD. The 60 day mortality was 2%. Thus, front line GCLAC is a well-tolerated, effective induction regimen for AML and advanced myelodysplastic or myeloproliferative disorders.

Improvements in the early death rate among 9380 patients with acute myeloid leukemia after initial therapy: A SEER database analysis

BACKGROUND

Acute myeloid leukemia (AML) is treated with conventional induction chemotherapy shortly after diagnosis for the majority of patients aged ≤ 65 years. A recent report suggested a substantial decline in the early, or 1-month, mortality rate in patients treated on clinical trials over the past 2 decades. It is unknown whether a similar improvement has been observed in the general population.

METHODS

The authors examined the 1-month mortality rate in a large population-based series of 9380 patients with AML who were aged ≤ 65 years and were diagnosed and treated with chemotherapy between 1973 and 2010.

RESULTS

A significant decline was observed in the 1-month mortality rate from 18.7% among patients diagnosed from 1973 through 1977 (95% confidence interval [95% CI], 16.4%-21.2%) to 5.8% for those diagnosed between 2008 and 2010 (95% CI, 4.5%-7.6%) (P <.001). The median overall survival improved significantly from 6 months (95% CI, 5 months-7 months) in 1973 to 1977 to 23 months (95% CI, 16 months-20 months) in 2008 to 2010 (P <.001). Although age and geographic variation were found to significantly influence the 1-month mortality for the period between 1973 and 1977, these differences in 1-month mortality were no longer significant among patients with AML who were treated more recently (2008-2010).

CONCLUSIONS

Over the past 4 decades, early mortality has become uncommon in younger patients (aged ≤ 65 years) with newly diagnosed AML undergoing induction chemotherapy. It is encouraging that the improvements noted in 1-month mortality rate among a selective cohort of patients in clinical trials have also been observed in a population-based analysis.

Isocitrate dehydrogenase 1 and 2 mutations induce BCL-2 dependence in acute myeloid leukemia

Mutant isocitrate dehydrogenase (IDH) 1 and 2 proteins alter the epigenetic landscape in acute myeloid leukemia (AML) cells through production of the oncometabolite (R)-2-hydroxyglutarate (2-HG). Here we performed a large-scale RNA interference (RNAi) screen to identify genes that are synthetic lethal to the IDH1(R132H) mutation in AML and identified the anti-apoptotic gene BCL-2. IDH1- and IDH2-mutant primary human AML cells were more sensitive than IDH1/2 wild-type cells to ABT-199, a highly specific BCL-2 inhibitor that is currently in clinical trials for hematologic malignancies, both ex vivo and in xenotransplant models. This sensitization effect was induced by (R)-2-HG-mediated inhibition of the activity of cytochrome c oxidase (COX) in the mitochondrial electron transport chain (ETC); suppression of COX activity lowered the mitochondrial threshold to trigger apoptosis upon BCL-2 inhibition. Our findings indicate that IDH1/2 mutation status may identify patients that are likely to respond to pharmacologic BCL-2 inhibition and form the rational basis for combining agents that disrupt ETC activity with ABT-199 in future clinical studies.

Cytogenetic heterogeneity negatively impacts outcomes in patients with acute myeloid leukemia

Clonal heterogeneity is a hallmark of malignant transformation. In acute myeloid leukemia, acquired cytogenetic abnormalities are important independent predictors of initial response to therapy, remission duration, and overall survival. However, whether the presence of multiple cytogenetically characterized clones affects outcomes in acute myeloid leukemia is still not well defined. The aim of this study was to assess the prognostic impact of cytogenetic clonal heterogeneity in acute myeloid leukemia. This analysis included 1403 newly diagnosed acute myeloid leukemia patients fit for intensive chemotherapy, aged between 15 and 88 years, enrolled on Southwest Oncology Group protocols. The presence of multiple cytogenetic clones was found in 164 (24%) patients with abnormal karyotype. The proportion of patients with clonal heterogeneity increased with age, being present in 20% of patients under 40 years of age, but in 30% of those aged over 70 years (P=0.03). Clonal heterogeneity was significantly more common in association with unfavorable karyotype. Clonal heterogeneity was associated with decreased response rates and inferior event-free, relapse-free and overall survival, and was confirmed as an independent predictor of poor prognosis in multivariable analysis. Subgroup analysis showed that clonal heterogeneity adds prognostic information particularly in the unfavorable karyotype group. Our results confirm the negative prognostic impact of clonal heterogeneity in acute myeloid leukemia patients with abnormal karyotype. (clinicaltrials.gov identifiers: 014343329; 01338974; 00899171; 1059734; 01059734; 00899743; 0143329; 00023777; 00085709; 01360125; 00004217).

Mcl-1 dependence predicts response to vorinostat and gemtuzumab ozogamicin in acute myeloid leukemia

Older adults with acute myeloid leukemia (AML) are commonly considered for investigational therapies, which often only benefit subsets of patients. In this study, we assessed whether BH3 profiling of apoptotic functionality could predict outcomes following treatment with vorinostat (histone deacetylase inhibitor) and gemtuzumab ozogamicin (GO; CD33-targeted immunoconjugate). Flow cytometry of BH3 peptide priming with Noxa (anti-apoptotic protein Mcl-1 modulator) correlated with remission induction (p=.026; AUC=0.83 [CI: 0.65-1.00; p=.00042]: AUC=0.88 [CI:0.75-1.00] with age adjustment) and overall survival (p=.027 logistic regression; AUC=0.87 [0.64-1.00; p=.0017]). This Mcl-1-dependence suggests a pivotal role of Bcl-2 family protein-mediated apoptosis to vorinostat/GO in AML patients.

Unsuccessful diagnostic cytogenetic analysis is a poor prognostic feature in acute myeloid leukaemia

Chromosome banding analysis is the gold standard method for the identification of recurrent cytogenetic abnormalities in acute myeloid leukaemia (AML). It allows stratification of AML patients into subgroups with distinct responses to therapy and survival. Unfortunately, a variety of issues hamper cytogenetic evaluation in c. 10% of cases [unsuccessful cytogenetics (UC)] and the outcome of these patients is poorly understood. To better define the significance of UC in patients with AML, we compared the baseline characteristics and the prognostic impact of 94 (6%) patients, whose standard metaphase analysis yielded unacceptable results, to the remaining 1403 AML patients with successful cytogenetic analysis treated on successive Southwestern Oncology Group protocols. The incidence of UC increased with age, with peak incidence in patients older than 60 years. These patients had a lower response rate to induction chemotherapy (complete remission rate of 43%) and dismal 5-year survival rates (16%), which was especially poor in patients older than 60 years (<5%). The complete remission and survival rates were similar to those seen in patients with unfavourable karyotype. The early death rate was not increased. These results suggest that UC increases with age and predict for poor outcomes, similar to the outcomes of patients with unfavourable karyotype.

Gemtuzumab ozogamicin in combination with vorinostat and azacitidine in older patients with relapsed or refractory acute myeloid leukemia: a phase I/II study

Epigenetic therapeutics such as the histone deacetylase inhibitor, vorinostat, and the DNA methyltransferase I inhibitor, azacitidine, enhance gemtuzumab ozogamicin efficacy in vitro. We therefore investigated vorinostat/azacitidine/gemtuzumab ozogamicin in 52 adults aged 50 years or over with acute myeloid leukemia requiring therapy for first relapse (remission duration ≤ 12 months) or primary refractory disease in a phase I/II trial. Vorinostat and gemtuzumab ozogamicin were escalated step-wise during the phase I portion of the trial. Vorinostat (400 mg/day orally from Days 1-9), azacitidine (75 mg/m(2)/day intravenously or subcutaneously from Days 1-7), and gemtuzumab ozogamicin (3 mg/m(2)/day intravenously on Days 4 and 8) were identified as the maximum tolerated dose. Among the 43 patients treated at this dose, 10 achieved a complete remission and 8 achieved a complete remission with incomplete blood count recovery, for an overall response rate of 41.9% (exact 95% confidence interval (CI): 27.0-57.9%). Four of these 18 patients (2 with complete remission and 2 with complete remission with incomplete blood count recovery) had persistence of minimal residual disease by flow cytometry at the time of best response. Four patients died within 28 days of treatment initiation. Median overall survival for the 18 patients achieving complete remission/complete remission with incomplete blood count recovery was significantly longer than for those 21 patients who failed therapy but lived at least 29 days after treatment initiation (224.5 days (range 70-798) vs. 95 days (range 36-900); P=0.0023). These data indicate that vorinostat/azacitidine/gemtuzumab ozogamicin has activity in this difficult-to-treat acute myeloid leukemia patient subset. (ClinicalTrials.gov: identifier 00895934).

Qualitative analysis of practicing oncologists' attitudes and experiences regarding collection of patient-reported outcomes

PURPOSE

There is growing interest in incorporating routine collection of patient-reported outcomes (PROs) into cancer care. Practicing oncologists are a stakeholder group whose views are not well characterized.

METHODS

We developed an interview guide after literature review and in-depth interviews with leaders in the field. We conducted 45-minute semistructured interviews with a diverse sample of medical oncologists identified through affiliation with the Quality Oncology Practice Initiative or a minority-based Community Clinical Oncology Program until thematic saturation. Multiple analysts independently reviewed and thematically coded verbatim transcripts.

RESULTS

Seventeen interviews were conducted with oncologists from 15 states. Emergent themes included variable understanding and experience with PROs. There was enthusiasm for the potential of PROs to improve the efficiency and thoroughness of the patient encounter. Fundamental concerns included information overload, possibility of identifying problems without access to intervention, depersonalization of the physician-patient encounter, cost, and inefficiency. Barriers identified included the need for buy-in from other stakeholders in the practice, lack of appropriate referral resources, staffing needs, and technology concerns. Few identified patient compliance, data sharing/privacy, or medical liability as a major barrier to implementation.

CONCLUSION

Practicing oncologists had variable understanding of the details of PROs but, when introduced to the concept, recognized utility in improving the efficiency and thoroughness of the patient encounter if implemented properly. The time is right to begin pilot testing such measures with community oncologists so they can lend their expertise to national discussions on which measures to use and how best to use them.