A phase 2, multicenter, clinical trial of CPX-351 in older patients with secondary or high-risk acute myeloid leukemia: PETHEMA-LAMVYX.

BACKGROUND: LAMVYX was a multicenter, single-arm, phase 2 trial designed to validate the safety and efficacy of CPX-351 in patients aged 60-75 years with newly diagnosed, secondary acute myeloid leukemia and to generate evidence on key issues not addressed in the preceding regulatory pivotal trial. METHODS: The primary end point of the study was the complete remission (CR)/CR with incomplete hematologic recovery (CRi) rate after induction. Eligible patients were recommended to undergo allogeneic hematopoietic stem cell transplantation after the first consolidation cycle. Alternatively, patients could undergo up to six maintenance cycles with CPX-351. RESULTS: Twenty-nine patients (49%; 95% exact confidence interval [CI], 37%-62%) patients achieved a CR/CRi after one or two cycles of induction, with a measurable residual disease negativity rate of 67% as assessed by centralized, multiparameter flow cytometry. Among patients who had serial next-generation sequencing analyses available, clearance of somatic mutations that were present at diagnosis was achieved in 7 (35%). The median follow-up among survivors was 16.8 months (range, 8.7-24.3 months). The median event-free survival was 3.0 months (95% CI, 1.4-7.3 months), and the median overall survival was 7.4 months (95% CI, 3.7-12.7 months). In landmark analyses at day +100 from diagnosis, the 1-year overall and event-free survival rate among patients who underwent allogeneic hematopoietic stem cell transplantation was 70% (95% CI, 47%-100%) and 70% (95% CI, 47%-100%), respectively. The corresponding values were 89% (95% CI, 71%-100%) and 44% (95% CI, 21%-92%), respectively, for patients who entered the maintenance phase. No significant longitudinal changes were observed in severity index or quality-of-life visual analog scale scores. CONCLUSIONS: The current data provide novel insights that might inform the clinical positioning and optimal use of CPX-351, complementing previous results (ClinicalTrials.gov identifier NCT04230239).

Evolving patterns and clinical outcome of genetic studies performed at diagnosis in acute myeloid leukemia patients: Real life data from the PETHEMA Registry.

BACKGROUND: There are no studies assessing the evolution and patterns of genetic studies performed at diagnosis in acute myeloid leukemia (AML) patients. Such studies could help to identify potential gaps in our present diagnostic practices, especially in the context of increasingly complex procedures and classifications. METHODS: The REALMOL study (NCT05541224) evaluated the evolution, patterns, and clinical impact of performing main genetic and molecular studies performed at diagnosis in 7285 adult AML patients included in the PETHEMA AML registry (NCT02607059) between 2000 and 2021. RESULTS: Screening rates increased for all tests across different time periods (2000-2007, 2008-2016, and 2017-2021) and was the most influential factor for NPM1, FLT3-ITD, and next-generation sequencing (NGS) determinations: NPM1 testing increased from 28.9% to 72.8% and 95.2% (p < .001), whereas FLT3-ITD testing increased from 38.1% to 74.1% and 95.9% (p < .0001). NGS testing was not performed between 2000-2007 and only reached 3.5% in 2008-2016, but significantly increased to 72% in 2017-2021 (p < .001). Treatment decision was the most influential factor to perform karyotype (odds ratio [OR], 6.057; 95% confidence interval [CI], 4.702-7.802), and fluorescence in situ hybridation (OR, 2.273; 95% CI, 1.901-2.719) studies. Patients ≥70 years old or with an Eastern Cooperative Oncology Group ≥2 were less likely to undergo these diagnostic procedures. Performing genetic studies were associated with a favorable impact on overall survival, especially in patients who received intensive chemotherapy. CONCLUSIONS: This unique study provides relevant information about the evolving landscape of genetic and molecular diagnosis for adult AML patients in real-world setting, highlighting the increased complexity of genetic diagnosis over the past 2 decades.

Immunosenescence: limitations of natural killer cell-based cancer immunotherapy.

Cancer is primarily considered a disease of old age. Immunosenescence refers to the age-associated changes in the immune system, and its contribution to the increased risk of cancer in old individuals has been discussed for many years. Natural killer (NK) cells are cytotoxic innate immune cells specialized in defence against tumour and virus-infected cells. NK cell cytotoxicity is the result of a fine balance between activating and inhibitory receptors. Several activating receptors have been identified that recognize different ligands frequently found over-expressed on tumour cells or virus-infected cells. The most important NK cell inhibitory receptors interact with major histocompatibility complex class I molecules expressed on almost all nucleated cells preventing NK cell-mediated lysis of healthy cells. NK cell immunosenescence is characterized by a redistribution of NK cell subsets, a diminished expression of several activating receptors and lower per-cell cytotoxicity. Altered expression of activating receptors has also been described in young and elderly cancer patients probably due to chronic exposure to ligands on tumour cells. Thus, the effect of both age and cancer may act synergistically to diminish NK cell-mediated tumour immunosurveillance. Different strategies harnessing the power of NK cells to target tumour cells have been designed including adoptive therapy with autologous or allogeneic expanded NK cells. In addition, checkpoint blockade of inhibitory receptors and the use of agonist antibodies to stimulate activating receptors are emerging areas of research. In this context, the effect of immunosenescence should be considered to improve the efficiency of cancer immunotherapy.

A prognostic model for survival after salvage treatment with FLAG-Ida +/- gemtuzumab-ozogamicine in adult patients with refractory/relapsed acute myeloid leukaemia.

The combination of fludarabine, cytarabine, idarubicin, and granulocyte colony-stimulating factor (FLAG-Ida) is widely used in relapsed/refractory acute myeloid leukaemia (AML). We retrospectively analysed the results of 259 adult AML patients treated as first salvage with FLAG-Ida or FLAG-Ida plus Gentuzumab-Ozogamicin (FLAGO-Ida) of the Programa Español de Tratamientos en Hematología (PETHEMA) database, developing a prognostic score system of survival in this setting (SALFLAGE score). Overall, 221 patients received FLAG-Ida and 38 FLAGO-Ida; 92 were older than 60 years. The complete remission (CR)/CR with incomplete blood count recovery (CRi) rate was 51%, with 9% of induction deaths. Three covariates were associated with lower CR/CRi: high-risk cytogenetics and t(8;21) at diagnosis, no previous allogeneic stem cell transplantation (allo-SCT) and relapse-free interval <1 year. Allo-SCT was performed in second CR in 60 patients (23%). The median overall survival (OS) of the entire cohort was 0·7 years, with 22% OS at 5-years. Four independent variables were used to construct the score: cytogenetics, FLT3-internal tandem duplication, length of relapse-free interval and previous allo-SCT. Using this stratification system, three groups were defined: favourable (26% of patients), intermediate (29%) and poor-risk (45%), with an expected 5-year OS of 52%, 26% and 7%, respectively. The SALFLAGE score discriminated a subset of patients with an acceptable long-term outcome using FLAG-Ida/FLAGO-Ida regimen. The results of this retrospective analysis should be validated in independent external cohorts.

Natural killer cell immunosenescence in acute myeloid leukaemia patients: new targets for immunotherapeutic strategies?

Several age-associated changes in natural killer (NK) cell phenotype have been reported that contribute to the defective NK cell response observed in elderly patients. A remodelling of the NK cell compartment occurs in the elderly with a reduction in the output of immature CD56(bright) cells and an accumulation of highly differentiated CD56(dim) NK cells. Acute myeloid leukaemia (AML) is generally a disease of older adults. NK cells in AML patients show diminished expression of several activating receptors that contribute to impaired NK cell function and, in consequence, to AML blast escape from NK cell immunosurveillance. In AML patients, phenotypic changes in NK cells have been correlated with disease progression and survival. NK cell-based immunotherapy has emerged as a possibility for the treatment of AML patients. The understanding of age-associated alterations in NK cells is therefore necessary to define adequate therapeutic strategies in older AML patients.

Biological relapse in multiple myeloma: Outcome and treatment strategies in a Spanish real-world setting.

Recommendations regarding the best time to start treatment in patients with relapsed/refractory multiple myeloma (RRMM) after biological relapse/progression (BR) are unclear. This observational, prospective, multicenter registry aimed to evaluate the impact on time to progression (TTP) of treatment initiation at BR versus at symptomatic clinical relapse (ClinR) based on the Spanish routine practice in adult patients with RRMM. Patients had two or less previous treatment lines and at least one previous partial response. Baseline characteristics and treatment outcomes were recorded, and survival was analyzed. Of 225 patients, 110 were treated at BR (TxBR group) and 115 at ClinR (TxClinR group) according to the investigators' criteria. The proportion of patients with higher ECOG, previous noncomplete remission (CR), and second relapse were significantly higher in the TxBR group compared to the TxClinR group. TheTxClinR group showed improved outcomes, including TTP, compared to the TxBR group. Progression-free survival increased in the TxClinR group (56.2 months) compared to the TxBR group (32.5 months) (p = 0.0137), and median overall survival also increased (p = 0.0897). Median TTP was significantly longer in patients relapsing from a CR (50.4 months) and in their first relapse (38.7 months) compared to those relapsing from a non-CR response (32.9 months) and in their second relapse (25.2 months). Physicians seemed to start treatment earlier in RRMM patients with poor prognosis features. Previous responses to anti-MM treatment and the number of prior treatment lines were identified as prognosis factors, whereby relapse from CR and first relapse were associated with a longer time to progression.

Cytokine profiles in acute myeloid leukemia patients at diagnosis: survival is inversely correlated with IL-6 and directly correlated with IL-10 levels.

BACKGROUND: Several evidences support the existence of cytokine deregulation in acute myeloid leukemia (AML) patients that may be associated with pathogenesis, disease progression and patient survival. METHODS: In the present study, we analyzed plasma levels of pro- and anti-inflammatory cytokines in AML patients and age-matched healthy donors. TNF-α, IL-6, IL-1ß, IL-2, IFN-γ, IL-17A, IL-12p70, IL-8, IL-10, IL-4 and IL-5 were analyzed using fluorescent bead-based technology and TGF-ß by ELISA technique. Because age-associated differences in cytokine profiles have been described, patients and healthy individuals were divided into two age groups: up to 65 years and over 65 years. RESULTS: Our results showed that plasma TNF-α, IL-6 and IL-10 levels were higher in AML patients from both groups of age. IL-8 was increased in AML patients less than 65 years while the plasma concentrations of IL-4, IL-5 and IL-12p70 were significantly higher only in elderly AML patients compared with aged-matched healthy controls. Moreover, plasma levels of IL-6 and IL-10 were associated with patient survival and event-free survival. CONCLUSIONS: An aberrant production of the pro-inflammatory cytokines IL-6 and TNF-α and the anti-inflammatory cytokine IL-10 is observed in AML patients. Low levels of IL-6 and high levels of IL-10 represent favorable prognostic factors for survival in AML patients. These results support the idea that cytokine deregulation may be useful as a marker for predicting clinical evolution in AML patients.

Decreased expression of DNAM-1 on NK cells from acute myeloid leukemia patients.

This study tested the hypothesis that the expression of CD112 and CD155 (DNAM-1 ligands) on leukemic blasts induces a decreased expression of the activating receptor DNAM-1 on natural killer (NK) cells from acute myeloid leukemia (AML) patients. DNAM-1 is a co-receptor involved in the activation of NK cell cytotoxicity after its interaction with its ligands CD112 and CD155 on target cells. Here we study the expression of DNAM-1 on NK cells and DNAM-1 ligands on blasts from AML patients stratified by age. The results demonstrate that NK cells from AML patients younger than 65 years have a reduced expression of DNAM-1 compared with age-matched controls. The analysis of DNAM-1 ligands showed a high expression of CD112 and CD155 on leukemic blasts. An inverse correlation between CD112 expression on leukemic blasts and DNAM-1 expression on NK cells was found. Furthermore, downregulation of DNAM-1 was induced on healthy donors' NK cells after in vitro culture with leukemic blasts expressing DNAM-1 ligands. In conclusion, these results support the hypothesis that receptor-ligand crosslinking downregulates DNAM-1 expression on NK cells from patients <65 years of age. Considering the relevance of DNAM-1 in NK recognition and killing of leukemic cells, the reduced expression of this receptor on NK cells from AML patients can represent an additional mechanism of tumor escape.

Human NK cells in acute myeloid leukaemia patients: analysis of NK cell-activating receptors and their ligands.

Natural killer (NK) cell activation is strictly regulated to ensure that healthy cells are preserved, but tumour-transformed or virus-infected cells are recognized and eliminated. To carry out this selective killing, NK cells have an ample repertoire of receptors on their surface. Signalling by inhibitory and activating receptors by interaction with their ligands will determine whether the NK cell becomes activated and kills the target cell. Here, we show reduced expression of NKp46, NKp30, DNAM-1, CD244 and CD94/NKG2C activating receptors on NK cells from acute myeloid leukaemia patients. This reduction may be induced by chronic exposure to their ligands on leukaemic blasts. The analysis of ligands for NK cell-activating receptors showed that leukaemic blasts from the majority of patients express ligands for NK cell-activating receptors. DNAM-1 ligands are frequently expressed on blasts, whereas the expression of the NKG2D ligand MICA/B is found in half of the patients and CD48, a ligand for CD244, in only one-fourth of the patients. The decreased expression of NK cell-activating receptors and/or the heterogeneous expression of ligands for major receptors on leukaemic blasts can lead to an inadequate tumour immunosurveillance by NK cells. A better knowledge of the activating receptor repertoire on NK cells and their putative ligands on blasts together with the possibility to modulate their expression will open new possibilities for the use of NK cells in immunotherapy against leukaemia.

Differentiation syndrome in patients with acute promyelocytic leukemia treated with all-trans retinoic acid and anthracycline chemotherapy: characteristics, outcome, and prognostic factors.

Differentiation syndrome (DS) can be a life-threatening complication in patients with acute promyelocytic leukemia (APL) undergoing induction therapy with all-trans retinoic acid (ATRA). Detailed knowledge about DS has remained limited. We present an analysis of the incidence, characteristics, prognostic factors, and outcome of 739 APL patients treated with ATRA plus idarubicin in 2 consecutive trials (Programa Español de Tratamientos en Hematología [PETHEMA] LPA96 and LPA99). Overall, 183 patients (24.8%) experienced DS, 93 with a severe form (12.6%) and 90 with a moderate form (12.2%). Severe but not moderate DS was associated with an increase in mortality. A bimodal incidence of DS was observed, with peaks occurring in the first and third weeks after the start of ATRA therapy. A multivariate analysis indicated that a WBC count greater than 5 x 10(9)/L and an abnormal serum creatinine level correlated with an increased risk of developing severe DS. Patients receiving systematic prednisone prophylaxis (LPA99 trial) in contrast to those receiving selective prophylaxis with dexamethasone (LPA96 trial) had a lower incidence of severe DS. Patients developing severe DS showed a reduced 7-year relapse-free survival in the LPA96 trial (60% vs 85%, P = .003), but this difference was not apparent in the LPA99 trial (86% vs 88%).

Risk-adapted treatment of acute promyelocytic leukemia with all-trans retinoic acid and anthracycline monochemotherapy: long-term outcome of the LPA 99 multicenter study by the PETHEMA Group.

A previous report of the Programa de Estudio y Tratamiento de las Hemopatías Malignas (PETHEMA) Group showed that a risk-adapted strategy combining all-trans retinoic acid (ATRA) and anthracycline monochemotherapy for induction and consolidation in newly diagnosed acute promyelocytic leukemia results in an improved outcome. Here we analyze treatment outcome of an enlarged series of patients who have been followed up for a median of 65 months. From November 1999 through July 2005 (LPA99 trial), 560 patients received induction therapy with ATRA plus idarubicin. Patients achieving complete remission received 3 courses of consolidation followed by maintenance with ATRA and low-dose chemotherapy. The 5-year cumulative incidence of relapse and disease-free survival were 11% and 84%, respectively. These results compare favorably with those obtained in the previous LPA96 study (P = .019 and P = .04, respectively). This updated analysis confirms the high antileukemic efficacy, low toxicity, and high degree of compliance of a risk-adapted strategy combining ATRA and anthracycline monochemotherapy for consolidation therapy.

Characterization of the DNAM-1, TIGIT and TACTILE Axis on Circulating NK, NKT-Like and T Cell Subsets in Patients with Acute Myeloid Leukemia.

Background: Acute myeloid leukemia (AML) remains a major clinical challenge due to poor overall survival, which is even more dramatic in elderly patients. TIGIT, an inhibitory receptor that interacts with CD155 and CD112 molecules, is considered as a checkpoint in T and NK cell activation. This receptor shares ligands with the co-stimulatory receptor DNAM-1 and with TACTILE. The aim of this work was to analyze the expression of DNAM-1, TIGIT and TACTILE in NK cells and T cell subsets in AML patients. Methods: We have studied 36 patients at the time of diagnosis of AML and 20 healthy volunteers. The expression of DNAM-1, TIGIT and TACTILE in NK cells and T cells, according to the expression of CD3 and CD56, was performed by flow cytometry. Results: NK cells, CD56- T cells and CD56+ T (NKT-like) cells from AML patients presented a reduced expression of DNAM-1 compared with healthy volunteers. An increased expression of TIGIT was observed in mainstream CD56- T cells. No differences were observed in the expression of TACTILE. Simplified presentation of incredibly complex evaluations (SPICE) analysis of the co-expression of DNAM-1, TIGIT and TACTILE showed an increase in NK and T cells lacking DNAM-1 and co-expressing TIGIT and TACTILE. Low percentages of DNAM-1-TIGIT+TACTILE+ NK cells and DNAM-1- TIGIT+TACTILE+ CD56- T cells were associated with a better survival of AML patients. Conclusions: The expression of DNAM-1 is reduced in NK cells and in CD4+ and CD8+ T cells from AML patients compared with those from healthy volunteers. An increased percentage of NK and T cells lacking DNAM-1 and co-expressing TIGIT and TACTILE is associated with patient survival, supporting the role of TIGIT as a novel candidate for checkpoint blockade.

Central nervous system involvement at first relapse in patients with acute promyelocytic leukemia treated with all-trans retinoic acid and anthracycline monochemotherapy without intrathecal prophylaxis.

BACKGROUND: The prevalence of and risk factors for central nervous system recurrence in patients with acute promyelocytic leukemia are not well established and remain a controversial matter. DESIGN AND METHODS: Between 1996 and 2005, 739 patients with newly diagnosed acute promyelocytic leukemia enrolled in two consecutive trials (PETHEMA LPA96 and LPA99) received induction therapy with all-trans retinoic acid and idarubicin. Consolidation therapy comprised three courses of anthracycline monochemotherapy (LPA96), with all-trans retinoic acid and reinforced doses of idarubicin in patients with an intermediate or high risk of relapse (LPA99). Central nervous system prophylaxis was not given. RESULTS: Central nervous system relapse was documented in 11 patients. The 5-year cumulative incidence of central nervous system relapse was 1.7% (LPA96 3.2% and LPA99 1.2%; p=0.09). The cumulative incidence was 0%, 0.8%, and 5.5% in low-, intermediate-, and high-risk patients, respectively. Relapse risk score (p=0.0001) and the occurrence of central nervous system hemorrhage during induction (5-year cumulative incidence 18.7%, p=0.006) were independent risk factors for central nervous system relapse. CONCLUSIONS: This study shows a low incidence of central nervous system relapse in patients with acute promyelocytic leukemia following therapy with all-trans retinoic acid and anthracycline without specific central nervous system prophylaxis. Central nervous system relapse was significantly associated with high white blood cell counts and prior central nervous system hemorrhage, which emerged as independent prognostic factors.

DNAM-1 and the TIGIT/PVRIG/TACTILE Axis: Novel Immune Checkpoints for Natural Killer Cell-Based Cancer Immunotherapy.

Natural killer (NK) cells are lymphocytes of the innate immune response characterized by their role in the destruction of tumor cells. Activation of NK cells depend on a fine balance between activating and inhibitory signals mediated by different receptors. In recent years, a family of paired receptors that interact with ligands of the Nectin/Nectin-like (Necl) family has attracted great interest. Two of these ligands, Necl-5 (usually termed CD155 or PVR) and Nectin-2 (CD112), frequently expressed on different types of tumor cells, are recognized by a group of receptors expressed on T and NK cells that exert opposite functions after interacting with their ligands. These receptors include DNAM-1 (CD226), TIGIT, TACTILE (CD96) and the recently described PVRIG. Whereas activation through DNAM-1 after recognition of CD155 or CD112 enhances NK cell-mediated cytotoxicity against a wide range of tumor cells, TIGIT recognition of these ligands exerts an inhibitory effect on NK cells by diminishing IFN-γ production, as well as NK cell-mediated cytotoxicity. PVRIG has also been identified as an inhibitory receptor that recognizes CD112 but not CD155. However, little is known about the role of TACTILE as modulator of immune responses in humans. TACTILE control of tumor growth and metastases has been reported in murine models, and it has been suggested that it negatively regulates the anti-tumor functions mediated by DNAM-1. In NK cells from patients with solid cancer and leukemia, it has been observed a decreased expression of DNAM-1 that may shift the balance in favor to the inhibitory receptors TIGIT or PVRIG, further contributing to the diminished NK cell-mediated cytotoxic capacity observed in these patients. Analysis of DNAM-1, TIGIT, TACTILE and PVRIG on human NK cells from solid cancer or leukemia patients will clarify the role of these receptors in cancer surveillance. Overall, it can be speculated that in cancer patients the TIGIT/PVRIG pathways are upregulated and represent novel targets for checkpoint blockade immunotherapy.

Consensus opinion for the selection and use of therapeutic products for the treatment of haemophilia in Spain.

The period between isolation of HIV in the early 1980s and the development of effective viral inactivation procedures able to eradicate the virus from the blood supply was long and unfortunately many recipients of blood-derived products became infected; this translated into a devastating impact on their quality of life, quality of care as well as on their life expectancy. Some years later, hepatitis C virus infection was identified as another known blood-borne disease complicating the treatment of haemophilia. Nowadays, the potential threat of emerging new pathogens has stressed the need to provide effective but primarily safe products with regard to infectious agents, as well as to regularly update therapeutic guidelines for haemophilia. The aim of the present publication was to review some of the crucial aspects related to the choice of haemostatic concentrates for the treatment of haemophilia and other inherited bleeding disorders, to analyse the current situation in the United States, Canada and European Union countries and to report the most relevant aspects of the Spanish consensus opinion of haemophilia-treating doctors for the use of therapeutic products for haemophilia recently issued. Essentially, it suggests that a gradual switch to recombinant concentrates may be a beneficial decision for patients with haemophilia and for the National Health Service.

In Vitro Culture with Interleukin-15 Leads to Expression of Activating Receptors and Recovery of Natural Killer Cell Function in Acute Myeloid Leukemia Patients.

Despite recent progress in the therapeutic approach of malignant hemopathies, their prognoses remain frequently poor. Immunotherapy could open a new window of great interest in this setting. Natural killer (NK) cells constitute an important area of research for hematologic malignancies, because this subpopulation is able to kill target cells spontaneously without previous sensitization, representing a novel tool in the treatment of them. Abnormal NK cytolytic function is observed in several hematological malignancies, including acute myeloid leukemia (AML) and myelodysplastic syndromes. Several mechanisms are involved in this abnormal function, such as decreased expression of activating receptors, increased expression of inhibitory receptors or defective expression of NK cell ligands on target cells. New immunotherapies are focused in identifying factors that could increase the expression of these activating receptors, to counteract inhibitory receptors expression, and therefore, to improve the NK cell cytotoxic capacities against tumor cells. In this work, we analyze the effect of interleukin (IL)-15 on the expression of NK cell-activating receptors that play a crucial role in the lysis of blasts from AML patients. Our results showed that IL-15 increased the surface expression of NKp30 on NK cells from healthy donors and AML patients with the consequent improvement of NK cell cytotoxicity. Besides, the upregulation of NKp30 induced by IL-15 is associated with an improvement of NK-mediated myeloid dendritic cells (DCs) maturation. NK cells cultured with IL-15 showed an upregulation of NKp30, which is associated with an increase anti-tumor activity and with an improved maturation of immature DCs. In our in vitro model, IL-15 exerted a great activating stimulus that could be used as novel immunotherapy in AML patients.

Causes and prognostic factors of remission induction failure in patients with acute promyelocytic leukemia treated with all-trans retinoic acid and idarubicin.

An understanding of the prognostic factors associated with the various forms of induction mortality in patients with acute promyelocytic leukemia (APL) has remained remarkably limited. This study reports the incidence, time of occurrence, and prognostic factors of the major categories of induction failure in a series of 732 patients of all ages (range, 2-83 years) with newly diagnosed APL who received all-trans retinoic acid (ATRA) plus idarubicin as induction therapy in 2 consecutive studies of the Programa de Estudio y Tratamiento de las Hemopatias Malignas (PETHEMA) Group. Complete remission was attained in 666 patients (91%). All the 66 induction failures were due to induction death. Hemorrhage was the most common cause of induction death (5%), followed by infection (2.3%) and differentiation syndrome (1.4%). Multivariate analysis identified specific and distinct pretreatment characteristics to correlate with an increased risk of death caused by hemorrhage (abnormal creatinine level, increased peripheral blast counts, and presence of coagulopathy), infection (age>60 years, male sex, and fever at presentation), and differentiation syndrome (Eastern Cooperative Oncology Group [ECOG] score>1 and low albumin levels), respectively. These data furnish clinically relevant information that might be useful for designing more appropriately risk-adapted treatment protocols aimed at reducing the considerable problem of induction mortality in APL.