Gilteritinib and the risk of intracranial hemorrhage: a case series of a possible, under-reported side effect.

Gilteritinib is currently approved for patients with relapsed/refractory AML with FLT3 mutations, based on the positive results of the pivotal ADMIRAL study. In ADMIRAL trial, no increased risk of bleeding was reported, but in the previous dose finding study, a single event of intracranial hemorrhage (ICH) was registered after exposure to subtherapeutic doses of gilteritinib. Here, we report the first case series on five ICHs diagnosed in patients with FLT3-mutated AML, occurred within the first month of exposure to gilteritinib. Our cohort included 24 patients treated in three Italian centers. Most of these ICH cases were non-severe and self-limiting, while one was fatal. This link with ICHs remains in any case uncertain for the presence of active AML. We further reported that an analysis of the post-marketing surveillance data (EudraVigilance) retrieved other 11 cases of ICHs present in the database after gilteritinib treatment. A causality assessment was performed according to the Dx3 method to evaluate the possibility that ICHs might be an actual side effect of gilteritinib. In conclusion, further research is needed to elucidate the potential role of gilteritinib in the pathogenesis of ICHs.

Phase II study of cladribine, idarubicin, and ara-C (CLIA) with or without sorafenib as initial therapy for patients with acute myeloid leukemia.

The addition of cladribine, or sorafenib to standard chemotherapy have each demonstrated improved survival in patients with newly-diagnosed acute myeloid leukemia (AML). We studied the combination of cladribine, idarubicin, and intermediate-dose cytarabine (CLIA) in patients ≤65 years of age with newly diagnosed AML, fit to receive intensive therapy. Cladribine (5 mg/m2) IV was administered on days (D)1-5, cytarabine (1 g/m2) on D1-5, and idarubicin (10 mg/m2) on D1-3. Sorafenib was added to the CLIA backbone for patients with FLT3-ITD mutated AML. 80 patients were enrolled: 65 with newly diagnosed AML and 15 with AML arising from previously treated MDS (ts-AML). The median age was 55 years (range, 21-65). CR + CRi was 83% (54/65) and 27% in the untreated and ts-AML cohorts, respectively; 74% and 75% of responding patients, respectively, had undetectable measurable residual disease (MRD). Among patients with FLT3-ITD mutated AML receiving CLIA+sorafenib, the CR + CRi rate was 95%, with 81% negative for MRD. With a median follow-up of 76 months, the 2- and 4-year OS of 57% and 50% compared to 20%, and 13% for ts-AML, respectively. Patients treated with CLIA+sorafenib had 2- and 5-year OS rates of 63% and 59%, respectively. The most common Grade ≥3 adverse events were infection/fever, elevated bilirubin, rash, and nausea. CLIA was safe and effective in young, fit patients with newly diagnosed AML with inferior outcomes among patients with ts-AML. The addition of sorafenib to CLIA in FLT3-ITD mutated AML resulted in high rates of durable remission and excellent long-term survival.

Durable Molecular Remission in an Elderly Patient Affected by Relapsed Ph'+ Acute Lymphoblastic Leukemia with T315I and Concomitant p190 and p210 Expression Achieved by Inotuzumab and Ponatinib.

An unmet clinical need currently exists for elderly patients with relapsed/resistant (R/R) Philadelphia (Ph) positive acute lymphoblastic leukemia (ALL), nearly all who have a very poor prognosis. This includes patients already exposed to the first or second generation tyrosine kinase inhibitors (TKIs) and therefore has few treatment options available. New immunotherapies and targeted agents have shown encouraging activity in R/R ALL irrespective of age. Inotuzumab (InO), a humanized anti-CD22 monoclonal antibody, has potentially beneficial clinical effects in patients with resistant and difficult-to-treat disease in whom prior TKIs have failed. However, InO, as a single agent, did not show durable response and longer progression free survival and overall survival in R/R Ph positive ALL patients compared with those treated with standard chemotherapy. We observed a durable molecular remission (7 months) in an elderly patient affected by Ph'+ ALL with T315I and concomitant p190 and p210 expression achieved by concomitant therapy of InO (for 4 cycles) and ponatinib (15 mg/daily) followed by ponatinib (15 mg/daily) only as maintenance therapy. These findings suggest that elderly R/R Ph positive patients who cannot proceed to the transplant might benefit by concomitant immunotherapy and TKIs aimed to deepen the responses and prolong CR and outcomes.

Identification of predictive factors for overall survival at baseline and during azacitidine treatment in high-risk myelodysplastic syndrome patients treated in the clinical practice.

The outcome of high-risk myelodysplastic syndrome (MDS) patients treated with 5-azacitidine (5-AZA) in the real-life setting remains largely unknown. We evaluated 110 MDS patients (IPSS intermediate 2/high) treated outside of clinical trials at a single institution between September 2003 and January 2017. Median duration of therapy was 9.5 cycles. The overall survival (OS) of the whole cohort was 66.1% at 1 year and 38.3% at 2 years. No differences in terms of OS were observed with regard to gender (p = 0.622) and age at baseline (< 65 years, 65-75, and > 75 years, p = 0.075). According to the IPSS-R, the very high-risk group had an inferior 2-year OS (17%) compared with intermediate-group patients (64%, p < 0.001). Transfusion independency at baseline was identified as a favorable prognostic factor on 1-year (66.8%) and 2-year OS (43.4%) (p < 0.001). After four cycles, the persistence of bone marrow blasts > 10% identified patients with a worse outcome, with a 2-year OS of 9.4% (p = 0.002). The occurrence of an infection during the first four cycles impacted on the 2-year OS (31.6% vs 58.3% in patients without infections, p = 0.032). Patients receiving at least 24 cycles of the drug have a 5-year OS of 38.2%. This analysis allowed to identify features at baseline or during treatment with 5-AZA associated with a different 2-year OS.

Ten-year outcome of chronic-phase chronic myeloid leukemia patients treated with imatinib in real life.

Imatinib, the first BCR/ABL kinase inhibitor approved for the treatment of chronic myeloid leukemia (CML), has changed the long-term outcome of patients affected by this disease. The aim of our analysis was to report, after a median follow-up of 10.2 years (range 5.8-14.8), the long-term outcome, efficacy, and safety of imatinib treatment (frontline and after interferon failure) in a single institution cohort of 459 patients with CML in chronic phase treated outside of clinical trials. The 10-year overall survival of the whole cohort was 77.1%, while the 10-year probability of dying due to CML and other causes was 7.8% and 16%, respectively. The prognostic value of the BCR-ABL1 ratio at 3 months (⩽ 10%) and of complete cytogenetic response and major molecular response at 1 year was confirmed also in the real-life practice. The EUTOS long-term survival score better stratified the baseline risk of dying of CML compared with other risk scores. Two hundred thirty-six (51.4%) patients achieved a deep molecular response during imatinib treatment after a median time of 4.57 years, and 95 (20.6%) had a stable deep molecular response maintained for at least 2 consecutive years. Imatinib was associated with a low rate of serious cardiovascular events and second neoplasia. This 10-year real-life follow-up study shows that imatinib maintains efficacy over time and that long-term administration of imatinib is not associated with notable cumulative or late toxic effects.

Incidence and evaluation of predisposition to cardiovascular toxicity in chronic myeloid leukemia patients treated with bosutinib in the real-life practice.

There is little information about cardiovascular adverse event (CV-AE) incidence in chronic myeloid leukemia (CML) patients treated with bosutinib in the real-life practice. We identified 54 consecutive CML patients treated with bosutinib, stratified according to the Systematic Coronary Risk Evaluation (SCORE) assessment, based on sex, age, smoking habits, systolic blood pressure, and total cholesterol levels. The 40-month cumulative incidence of CV-AEs was 25.2 ± 8.1%. Patients with the SCORE of high-very high showed a significantly higher incidence of CV-AEs (55 ± 12.9% vs 9 ± 9.5%; p = 0.002). Overall, 9 CV-AEs were reported, with 2 deaths attributed to CV-AE. In conclusion, the SCORE assessment before starting treatment is helpful in identifying CV-AE high-risk patients during bosutinib treatment.

Impact of comorbidities and body mass index in patients with myelofibrosis treated with ruxolitinib.

Comorbidities defined by the Charlson comorbidity index (CCI) and body mass index (BMI) are significantly associated with outcome in patients who receive continuous treatment with tyrosine kinase inhibitors. We evaluated the impact of CCI and BMI on responses, drug-related toxicities, and outcome in a cohort of 402 patients with myelofibrosis (MF) treated with ruxolitinib in 23 European Hematology Centers. Comorbidities were evaluable in all 402 patients. A higher (≥ 3) CCI did not correlate with a lower spleen reduction at any time (p = 0.68) or symptoms' response (p = 0.11), but influenced the onset of anemia during the first 3 months of treatment and later (p = 0.02 and p = 0.03, respectively) in patients without anemia baseline. BMI was evaluable in 380 patients and did not correlate with differences in spleen and symptoms response (p = 0.57 and p = 0.49, respectively). A higher CCI and a lower BMI correlated also with a reduced overall survival (p < 0.001 and p = 0.02, respectively). The achievement of a spleen response at 6 months could counterbalance the negative impact of comorbidities, while patients who were underweight when starting ruxolitinib and did not achieve a spleen response at 6 months were projected to the worse outcome. In MF patients treated with ruxolitinib, BMI and comorbidities did not influence the achievement of spleen/symptom responses, but they contributed to the early identification of patients who deserve a strict monitoring during treatment.

Maintenance therapy in AML: The past, the present and the future.

Curative treatment in acute myeloid leukemia (AML) depends on successful induction therapy to achieve a complete remission (CR), and subsequent post-remission therapy to prevent relapse. High relapse rates after consolidation therapy and after allogeneic stem cell transplant contribute to suboptimal outcomes in AML patients, and continue to represent a difficult challenge. Effective maintenance therapy could play an important role in prolonging the remission interval in the post-consolidation setting, especially in high risk AML patients. Maintenance treatment approaches based on conventional chemotherapy, immunotherapy, hypomethylating agents, and targeted small molecules have been explored in this setting, but no data so far have been convincing enough to establish this approach as the standard of care. However, ongoing and future studies including novel targeted therapies may demonstrate promising efficacy that could facilitate incorporation of maintenance therapy into clinical practice. In this review we summarize previous and ongoing approaches of maintenance therapy in AML and discuss the most promising strategies.

Treatment-free remission in chronic myeloid leukemia.

Tyrosine kinase inhibitors (TKIs) represent a major breakthrough in the treatment of chronic myeloid leukemia (CML). Thanks to these agents, CML has been transformed from a disease with limited treatment options and a dismal prognosis into a more indolent disease with survival comparable to that of the general population. The need for ongoing TKI therapy remains controversial for several reasons, including cost and toxicity. Studies in CML patients with a sustained deep molecular response have demonstrated that stopping TKI therapy is feasible and safe. Given the heterogeneity of results reported in clinical trials, practice guidelines for optimal patient selection and proper monitoring after discontinuation of TKIs are proposed outside of clinical trials. Current data available show that 40% to 60% of patients who stop therapy relapse; molecular relapses typically occur within 6 months, but nearly all relapsing patients regain response upon reinitiation of the TKI. Several factors that predict for relapse have been investigated. Duration of prior TKI therapy, achievement of deep molecular response, depth of molecular response, prior interferon treatment, and Sokal risk score have been shown to be potential predictors for relapse. Leukemia stem cells that are resistant to TKIs, and that persist despite undetectable BCR/ABL1 transcript levels, likely are responsible for disease relapse after discontinuation. Efforts geared toward better identification of low levels of BCR/ABL1 transcript using new techniques such as digital polymerase chain reaction, along with eradicating CML clones using combination therapies with agents such as pegylated interferon or venetoclax with TKIs, will hopefully lead to a functional cure of this disease.

Changes in estimated glomerular filtration rate in chronic myeloid leukemia patients treated front line with available TKIs and correlation with cardiovascular events.

We investigated the median estimated glomerular filtration rate (eGFR) changes in chronic myeloid leukemia (CML) patients treated front line with tyrosine kinase inhibitors (TKIs). A large cohort of 397 patients-320 treated front line with imatinib, 25 with dasatinib, and 53 with nilotinib-was retrospectively analyzed at a single institution. The eGFR was calculated according to the Chronic Kidney Disease Epidemiology Collaboration equation for all patients at baseline and then at 6 and 12 months, and at the last follow-up. Taking into account eGFR changes during the first year of treatment and excluding other possible cardiovascular risk factors, we considered also the percentage of cardiovascular events in patients with modifications of this single parameter. Imatinib induced a decrease in median eGFR (p = 0.01): 42 patients treated with imatinib had a cardiovascular event, related to modification of eGFR, in the absence of other cardiovascular risk factors. In patients treated with nilotinib, the median eGFR did not decline from baseline: only 1 patient experienced an ischemic event, but the eGFR remained unchanged. In patients treated with dasatinib, the mean eGFR did not change significantly: 3 patients experienced a cardiac ischemic event, but in all patients the eGFR remained unchanged over time, while advanced age and metabolic alterations contributed to the ischemic events. This long-term follow-up has documented that imatinib may induce changes in the eGFR, which may contribute to the onset of ischemic events. Further analyses on larger series of CML patients are required to conclusively define the potential renal toxicity of second generation TKIs and the consequent risk of developing ischemic events.

Prolonged treatment with arsenic trioxide (ATO) and all-trans-retinoic acid (ATRA) for relapsed acute promyelocytic leukemia previously treated with ATRA and chemotherapy.

Prolonged therapy with all-trans-retinoic acid (ATRA) and arsenic trioxide (ATO) is highly effective in newly diagnosed acute promyelocytic leukemia (APL) but there is limited data on the efficacy of this regimen in the relapse setting. We report here on 22 APL patients treated with prolonged ATRA-ATO therapy at the time of disease relapse. Twenty patients obtained molecular complete remission (CRm) after 2 cycles (90%). Of these, two patients underwent hematopoietic stem cell transplant (HSCT) while the remaining proceeded to receive additional cycles (up to a total of 5) of ATRA-ATO. With a median follow-up of 58 months from the time of relapse (range: 21-128 months), the 4-year OS probability was 0.85 (95% CI 0.61-0.94), DFS was 0.74 (95% CI 0.49-0.88), and EFS 0.68 (95% CI 0.45-0.83). Two patients were resistant to ATRA-ATO salvage and five relapsed at a median of 19 months. Of these, four died due to progressive disease while three relapsed achieved a new CRm after further salvage therapy. This experience confirms the potentially curative effect of prolonged ATRA-ATO therapy in relapsed APL, especially in patients with long first complete remission.

Clinical results according to age in patients with chronic myeloid leukemia receiving imatinib frontline: The younger, the later, the worse?

OBJECTIVES: To evaluate differences in clinical results according to age among patients with chronic myeloid leukemia (CML). METHODS: 207 consecutive CML patients treated with imatinib frontline were revised, dividing them in young adults (>20 < 45 years) (YA), middle-aged adults (≥45 < 65 years) (MA) and elderly (≥65 years) (EL). RESULTS: Cumulative incidence of complete cytogenetic response (CCyR) and major molecular response (MMolR) were significantly higher in MA compared with YA and EL (P < .001 for CCyR and P = .001 for MMolR). Number of total events was lower in MA (8 [11.1%] vs 21 [34.4%] in YA and 28 [37.8%] in EL, P = .001): no difference was observed for blastic evolution (P = .478). Number of deaths was higher in the EL (12 [16.2%] vs 2 [3.2%] in YA and 0 in MA, P < .001): however, 11/12 deaths in EL were not related to CML. The PFS curve in MA was significantly longer than in YA and in EL (P = .02). The OS curve in EL was significantly shorter than in YA and in MA (P < .001). CONCLUSIONS: Age at diagnosis influences significantly the course of CML patients treated with imatinib: a possible explanation of the counterintuitive worse course in YA is the delayed diagnosis compared to elderly.

Impact of exclusion criteria for the DASISION and ENESTnd trials in the front-line treatment of a 'real-life' patient population with chronic myeloid leukaemia.

Both Dasision and ENESTnd trials had many exclusion criteria, with a possible selection bias compared with the real-life. To address the impact of this bias on the first-line treatment in the current clinical practice, we revised 207 unselected newly diagnosed chronic phase chronic myeloid leukaemia (CML) patients [M/F 108/99, median age 58.8 years, interquartile range 42.3-70.2] treated with front-line imatinib from June 2002 to June 2013 at our Institution, and evaluated how many of them would have been excluded from enrolment in the two trials. Twenty-eight patients (13.5%) should have been excluded by both trials because of polycomorbidities (12), severe cardiomyopathy (five), age > 80 with frailty (three), drug abuse (two) or other severe concomitant diseases (six). In addition, eight patients should have been excluded by Dasision due to isolated chronic obstructive broncopulmonar disease, and 19 patients should have been excluded by ENESTnd due to isolated diabetes (10), arrhythmia (four), acute myocardial infarction > 6 months before CML diagnosis (two), chronic pancreatic disease (two) and peripheral arterial obstructive disease (one). On the whole, 36 patients (17.4%) would have been excluded by Dasision trial and 47 (22.7%) by ENESTnd trial. The patients potentially not eligible for both trials were significantly older and with imatinib had a worse outcome compared with patients potentially eligible. Our data highlight that an automatic transposition of results available in clinical controlled trials into the frontline real-life management of CML patients should be regarded with caution. Copyright © 2015 John Wiley & Sons, Ltd.

Ruxolitinib in clinical practice for primary and secondary myelofibrosis: an analysis of safety and efficacy of Gruppo Laziale of Ph-negative MPN.

Ruxolitinib, a JAK1 and JAK2 inhibitor, has been tested and approved for the treatment of primary and secondary myelofibrosis (MF). Aim of our study is to report safety and efficacy of ruxolitinib in 98 patients affected by MF treated outside clinical trials and collected and treated consecutively by the Lazio Cooperative Group for Ph negative myeloproliferative diseases.There were 45 males and 53 females; median age was 61.8 years (range 35.3-88). Forty-five patients were diagnosed as primary MF and 53 as secondary MF. Seventy-seven patients (78.5%) experienced constitutional symptoms at baseline, and out of 94 patients tested, 66 (70%) were JAK2V617F mutated. Overall, 40 patients received hydroxyurea as firstline treatment, 30 patients received other chemotherapeutic approaches, whereas 28 were treated with ruxolitinib frontline. Median time from diagnosis to start of ruxolitinib in the whole cohort was 34.6 months. Fifty-eight patients (59%) required a dose reduction during the first 3 months due to hematological toxicity in the majority of cases. At 48 weeks, 52% of patients obtained a clinical benefit: of them 7 patients (7%) had a CR, 10 (10%) a PR, 6 patients (6%) a CI, and 28 patients (28.5%) a spleen response. Overall, 66% of patients had disappearance of baseline symptoms burden. After 1 year, of 72 evaluable patients, 52% achieved and maintained a clinical benefit. Adverse events of special interest at any grade included anemia (39.7%), thrombocytopenia (25.5%), infections (16.3%, of which 10 were bronchopneumonia), fluid retention (3%), diarrhea (2%) and abdominal pain (2%). After a median follow-up of 16 months from start of ruxolitinib, median daily dose decreased to 10 mg BID and 21 patients (21%) discontinued the drug. The results of this retrospective multicentric analysis confirmed the efficacy of ruxolitinib outside clinical trials with more than half of treated patients achieving and maintaining a clinical benefit and most of them reporting relief from symptoms.

Application of systematic coronary risk evaluation chart to identify chronic myeloid leukemia patients at risk of cardiovascular diseases during nilotinib treatment.

Nilotinib is currently approved for the treatment of chronic myeloid leukemia (CML) in chronic (CP) and accelerated phase (AP) after failure of imatinib and in newly diagnosed patients. Atherosclerotic events were retrospectively reported in patients with baseline cardiovascular risk factors during nilotinib treatment. We estimated the risk of developing atherosclerotic events in patients treated with second or first-line nilotinib, with a median follow-up of 48 months, by retrospectively applying the SCORE chart proposed by the European Society of Cardiology (ESC) and evaluating risk factors at baseline (diabetes, obesity, smoking, and hypertension). Overall, we enrolled in the study 82 CP patients treated frontline (42 CP patients at the dose of 600 mg BID) or after failure of other tyrosine kinase inhibitors (40 CP patients treated with 400 mg BID). The SCORE chart is based on the stratification of sex (male vs female), age (from 40 to 65 years), smoker vs non-smoker, systolic pressure (from 120 to 180 mm Hg), and cholesterol (measured in mmol/l, from 150 to 300 mg/dl). For statistical purposes, we considered patients subdivided in low, moderate, high (with a score >5), and very high risk. There were 48 males and 34 females, median age 51 years (range 22-84). According to WHO classification, 42 patients were classified as normal weight (BMI <25), 26 patients were overweight (BMI 26 ≤ 30), and 14 were obese (BMI >30). Retrospective classification according to the SCORE chart revealed that 27 patients (33 %) were in the low-risk category, 30 patients (36 %) in the moderate risk category, and 24 patients (29 %) in the high risk. As regards risk factors, we revealed that 17 patients (20.7 %) had a concomitant type II controlled diabetes (without organ damage), 23 patients (28 %) were smokers, 29 patients (35 %) were receiving concomitant drugs for hypertension, and 15 patients (18 %) had concomitant dyslipidemia. Overall, the cumulative incidence of atherosclerotic events at 48 months was 8.5 % (95 % CI, 4.55-14.07): None of the low-risk patients according to the SCORE chart experienced atherosclerotic events compared to 10 % in the moderate risk category and 29 % in the high risk (p = 0.002). Atherosclerotic-free survival was 100, 89, and 69 % in the low, moderate, and high-risk population, respectively (p = 0.001). SCORE chart evaluation at disease baseline could be a valid tool to identify patients at high risk of atherosclerotic events during nilotinib treatment.

Incidence of persistent/late chronic anemia in newly diagnosed patients with chronic myeloid leukemia responsive to imatinib.

In patients with chronic myeloid leukemia (CML) responsive to imatinib, it is still unknown whether the long-lasting treatment could induce the appearance of a persistent/late chronic anemia. To highlight this issue, we revised 128 patients with CML (M/F 64/64, median age at diagnosis 56.9 years, interquartile range 43.0-69.3) treated at our Institution with 1st line imatinib for at least 36 months and in stable complete cytogenetic response. At the 36th month of imatinib, a chronic anemia (Hb < 12 g/dl for > 6 months) was present in 38/128 patients (29.6%): the anemia was moderate (Hb > 8 ≤ 10 g/dl) in 12 patients (9.3%) and mild (Hb > 10 < 12 g/dl) in 26 patients (20.3%). All patients with persistent/late chronic anemia had a low reticulocyte count and 8/38 a condition of iron deficiency without clinical and instrumental signs of chronic blood loss. Four out of 38 patients (10.5%) needed red cell transfusions during the follow-up. At a landmark analysis from the 36th month of imatinib treatment, cumulative 4-year overall survival (OS) for patients with chronic anemia was 94.4% (CI 95% 83.8-100) compared to 93.5% (CI 95% 87.2-99.8) for patients without chronic anemia (P = 0.617). In conclusion, the occurrence of a late chronic anemia during long-lasting treatment with imatinib has been observed in about 30% of our responsive patients: its occurrence does not seem to affect OS, but its real impact should be evaluated on a larger cohort of patients.

Catheter-associated bloodstream infections and thrombotic risk in hematologic patients with peripherally inserted central catheters (PICC).

PURPOSE: The use of peripherally inserted central catheters (PICC) as an alternative to other central venous access devices (CVAD) is becoming very frequent in cancer patients. To evaluate the impact of complications associated to these devices in patients with hematologic malignancies, we revised the catheter-related bloodstream infections (CRBSI) and the catheter-related thrombotic complications (CRTC) observed at our institute between January 2009 and December 2012. METHODS: A total of 612 PICCs were inserted into 483 patients at diagnosis or in subsequent phases of their hematologic disease. PICCs were successfully inserted in all cases. The median duration of in situ PICC placement was 101 days (interquartile range, 48-184 days). RESULTS: A CRBSI occurred in 47 cases (7.7 %), with a rate of 0.59 per 1000 PICC days. A CRTC was recorded in 16 cases (2.6 %), with a rate of 0.20 per 1000 PICC days. No serious complication was associated to these events. Cox regression analyses of variables associated to CRBSIs and to CRTCs showed that only the type of disease (acute leukemia compared to other diseases) was significantly associated to a higher incidence of CRBSIs, while no feature was predictive for a higher risk of CRTCs. CONCLUSIONS: PICCs represent a useful and safe alternative to conventional CVAD for the management of patients with hematologic malignancies.

Negative prognostic value of CD34 antigen also if expressed on a small population of acute promyelocytic leukemia cells.

Potential clinical significance of CD34 expression in acute promyelocitic leukemia (APL) has not been deeply investigated. We hereby analyzed the clinico-biological features and treatment outcome of APL patients in relation to CD34 expression, even when expressed in a small subpopulation: 114 APL patients homogeneously treated with the AIDA schedule were included in the study and prognostic correlation with respect to CD34 expression, both when expressed in association with CD2 and as isolated expression (cutoff ≥2 to <10 % or ≥10 %), were investigated. CD34 was associated to CD2 in 30 patients and was isolated in 19 patients. When compared to the CD34-negative population, CD34/CD2 expression identified a subgroup with characteristic features: M3 variant subtype (26 vs 7 % in the negative group, p = 0.02), bcr3 transcript subtype (73 vs 32 %, p = 0.001), high risk according to the risk of relapse (66 vs 17 %, p = 0.002), high incidence of differentiation syndrome (26 vs 12 %, p = 0.01), lower overall survival (88 vs 95 %), and a significantly higher rate of relapse (22 vs 13.8 %, p = 0.05). We then evaluated the prognostic value of isolated CD34 expression: it was detected in nine patients with a cutoff of expression ≥10 % and in 10 patients with a cutoff ≥2 but <10 %. Isolated CD34 positivity identified a subgroup with a classic morphology (79 %), bcr1 prevalence (53 %), higher rate of relapse (37 vs 13.8 % in the negative group, p = 0.002), higher incidence of differentiation syndrome (55 vs 12 %, p = 0.03), and lower overall survival (60 vs 95 %, p = 0.001). The results of our study confirm that CD34/CD2 expression characterizes a subset of APL with a high WBC count and a variant morphological subtype, associated with an unfavorable clinical course. We also show that the isolated expression of CD34, even at a low cutoff, identifies a group of classic APL with a negative prognosis. Further studies aimed at identifying other molecular signatures in CD34-positive patients are needed in order to optimize the therapeutic strategy for this subset of patients.