Second Neoplasms in Italian Patients with Hairy Cell Leukemia after Treatment with Cladribine: A Multicenter Investigation and Literature Review.

Concern has emerged about the prevalence of second cancers among patients with hairy cell leukemia (HCL) treated with purine analogs. We investigated 513 patients with HCL treated with cladribine over the last 30 years at 18 Italian centers and calculated their standardized incidence ratios (SIRs). We identified 24 patients with a second cancer diagnosed at a median time from treatment with cladribine of 59.9 months (range: 9.2-169.7 months). All patients with solid neoplasms presented with a limited-stage disease, except four cases of locally advanced cancer; multiple myeloma patients had a smoldering disease, while lymphoma patients had stage Ie and stage IV diseases. Response to therapy was complete in 19 cases; 1 patient is still receiving treatment for a relapsing bladder disease, while 2 patients progressed during treatment and died. These two patients died from unrelated causes: one from infection and one due to surgery complications. The median OS from HCL was 98.5 months (range: 38.4-409.2 months), while the median OS from second cancer was 27.6 months (range: 1-117.8 months). The SIR was 0.86 (95% CI: 0.54-1.30) for males and 1.13 (95% CI: 0.36-2.73) for females: no statistically significant differences were highlighted. We were not able to demonstrate an excess of second cancer or a significant association with the specific studied neoplasm.

Long-term follow-up of cladribine treatment in hairy cell leukemia: 30-year experience in a multicentric Italian study.

Hairy cell leukemia (HCL) is a rare lymphoproliferative disease with an excellent prognosis after treatment with cladribine (2CDA), although relapse may occur during follow-up. The aim of the study is to review the efficacy, safety, long-term remission rate, and overall survival (OS) in those patients who received 2CDA as first-line treatment. We retrospectively reviewed data of HCL patients treated with 2CDA between March 1991 and May 2019 at 18 Italian Hematological centers: 513 patients were evaluable for study purpose. The median age was 54 years (range 24-88) and ECOG was 0 in 84.9% of cases. A total of 330 (64.3%) patients received 2CDA intravenously and 183 (35.7%) subcutaneously. ORR was 91.8%: CR was obtained in 335 patients (65.3%), PR in 96 (18.7%), and hematological response in 40 (7.8%) patients; in 42 (8.2%) no response was observed. Hemoglobin value (p = 0.044), frequency of circulating hairy cells (p = 0.039), recovery of absolute neutrophil count (p = 0.006), and normalization of spleen (p ≤ 0.001) were associated with CR compared to PR in univariable analysis. At a median follow-up of 6.83 years (range 0.04-28.52), the median time to relapse was 12.2 years. A significant difference in duration of response was identified between patients that obtained a CR and PR (19.4 years versus 4.8 years, p < 0.0001). Non-hematological grade 3 or higher early toxicity was reported in 103 (20.1%) patients. Median OS was not reached: 95.3%, 92.4%, and 81.8% of patients were estimated to be alive at 5, 10, and 15 years, respectively. Forty-nine patients died (9.5%), following an infection in 14 cases (2.7%), natural causes in 14 (2.7%), cardiovascular events in 13 (2.5%), a second neoplasm in 6 (1.2%), and progression of HCL in 2 cases (0.4%). Following treatment of HCL with 2CDA, 80% of patients are estimated to be alive 15 years after diagnosis.

Prospective cardiac magnetic resonance imaging survey in myelodysplastic syndrome patients: insights from an Italian network.

We prospectively evaluated changes in cardiac and hepatic iron overload (IO) and in morpho-functional cardiac parameters and myocardial fibrosis by magnetic resonance imaging (MRI) in patients with low-risk and intermediate-1-risk myelodysplastic syndromes (MDS). Fifty patients enrolled in the Myocardial Iron Overload in MyElodysplastic Diseases (MIOMED) study were followed for 12 months. IO was quantified by the T2* technique and biventricular function parameters by cine images. Macroscopic myocardial fibrosis was detected by late gadolinium enhancement technique. Twenty-eight patients (71.89±8.46 years; 8 females) performed baseline and follow-up MRIs. Thirteen patients had baseline hepatic IO, with a higher frequency among transfusion-dependent patients. Out of the 15 patients with a baseline MRI liver iron concentration <3 mg/g/dw, two (non-chelated) developed hepatic IO. Thirteen (46.4%) patients had an abnormal T2* value in at least one myocardial segment. One patient without hepatic IO and non-transfused had baseline global T2* <20 ms. Among the 15 patients with no baseline myocardial IO (MIO), 2 worsened. There was a significant increase in both left and right ventricular end-diastolic volume indexes. Thirty-six percent of patients showed myocardial fibrosis correlating with aging. Two new occurrences were detected at the follow-up. In conclusion, by a more sensitive segmental approach, MIO is quite frequent in MDS patients and it can be present also in non-transfused patients and in absence of detectable hepatic iron. The incidence of cardiac and hepatic IO and of myocardial fibrosis and the increase in biventricular volumes after a 12-month interval suggest performing periodic MRI scans to better manage MDS patients.

Outcome of very elderly chronic myeloid leukaemia patients treated with imatinib frontline.

Very elderly (> 75 years) chronic myeloid leukaemia (CML) patients at diagnosis are sometimes treated with different doses of imatinib (IM) based on concomitant diseases and physicians' judgement. However, data on long-term follow-up of these patients are still lacking. To investigate treatment response and outcome, we retrospectively revised an Italian database of 263 very elderly CML patients receiving IM from the time of diagnosis. Median age at diagnosis was 78.5 years and 56% of patients had 2 or 3 comorbidities. A complete haematological and cytogenetic response were achieved in 244 (92.8%) and 184 (69.9%) patients, respectively. In 148 cases (56.2%), a major molecular response was observed, which was deep in 63 cases (24%). A blastic phase occurred in 11 patients (4.2%). After a median follow-up of 45.0 months, 93 patients have died (9 from disease progression) and 104 (39.5%) are still in treatment with IM. Incidence of grades 3-4 haematological and non-haematological toxicity was similar to those reported in younger patients. Five-year event-free survival was 54.5% and 45.2% in patients ≤ 80 years and > 80 years, respectively (p = 0.098). Five years OS was 75.7% and 61.6% in patients ≤80 years and > 80 years, respectively (p = 0.003). These findings show that IM plays an important role in frontline treatment of very elderly CML patients without increased toxicity and any effort to treat these patients with standard doses should be made in order to achieve responses as in younger subjects.

Early mortality in myeloma patients treated with first-generation novel agents thalidomide, lenalidomide, bortezomib at diagnosis: A pooled analysis.

INTRODUCTION: Early toxic death (≤60 days of diagnosis) in elderly multiple myeloma (MM) patients is attributable to active disease, age and co-morbidities. Rate of early toxic deaths is 10% with conventional chemotherapy mainly due to infection and renal failure. Novel agents have improved MM outcome at the expense of newer toxicity. METHODS: We analyzed 1146 individual patient data to assess toxic deaths during induction treatment with first-generation novel agents thalidomide, lenalidomide, bortezomib. RESULTS: During first-line therapy, 119/1146 patients (10%) died for any cause, and 47/1146 (4%) due to toxicity, including 12/1146 (1%) early deaths. The 24-month cumulative incidence was 4.1% without any difference between bortezomib (18/503 patients, 4%) and lenalidomide (29/643patients, 5%; p = 0.31). Toxic deaths occurred in 34/1039 (3%) patients <80 years and 13/107 (12%) patients ≥80 years. Causes were cardiac events (28%), infections (26%) and vascular complications (15%). In a multivariate analysis, older age and unfavorable ISS stage increased the risk of death. CONCLUSION: First-generation novel agents significantly reduced toxic deaths compared to conventional chemotherapy. One third of deaths during first-line therapy were due to cumulative drug-related toxicities, thus supportive approaches and prevention strategies should be optimized. The higher mortality rate for toxicity in octogenarians confirms the need for a careful frailty assessment.

Rituximab plus bendamustine as front-line treatment in frail elderly (>70 years) patients with diffuse large B-cell non-Hodgkin lymphoma: a phase II multicenter study of the Fondazione Italiana Linfomi.

We conducted a phase II study to assess activity and safety profile of bendamustine and rituximab in elderly patients with untreated diffuse large B-cell lymphoma (DLBCL) who were prospectively defined as frail using a simplified version of the Comprehensive Geriatric Assessment (CGA). Patients had to be over 70 years of age, with histologically confirmed DLBCL. Frail patients were those younger than 80 years with a frail profile at CGA or older than 80 years with an unfit profile. Treatment consisted of 4-6 courses of bendamustine [90 mg/m2 days (d)1-2] and rituximab (375 mg/m2 d1) administered every 28 days. Other main study end points were complete remission rate and the rate of extra-hematologic adverse events. Forty-nine patients were enrolled of whom 45 were confirmed eligible. Overall, 24 patients achieved a complete remission (53%; 95%CI: 38-68%) and the overall response rate was 62% (95%CI: 47-76%). The most frequent grade 3-4 adverse event was neutropenia (37.8%). Grade 3-4 extra-hematologic adverse events were observed in 7 patients (15.6%; 95%CI: 6.5-29.5%); the most frequent was grade 3 infection in 2 patients. With a median follow up of 33 months (range 1-52), the median progression-free survival was ten months (95%CI: 7-25). The study shows promising activity and manageable toxicity profile of BR combination as first-line therapy for patients with DLBCL who are prospectively defined as frail according to a simplified CGA, as adopted in this trial (clinicaltrials.gov identifier: 01990144).

Italian real-life experience with brentuximab vedotin: results of a large observational study of 40 cases of relapsed/refractory systemic anaplastic large cell lymphoma.

Between November 2012 and July 2014, in accordance with national law 648/96, brentuximab vedotin was available in Italy for patients with relapsed systemic anaplastic large cell lymphoma outside a clinical trial context. A large Italian observational retrospective study was conducted on the use of brentuximab vedotin in everyday clinical practice to check whether clinical trial results are confirmed in a real-life context. The primary endpoint of this study was best response; secondary endpoints were the overall response rate at the end of the treatment, duration of response, survival and safety profile. A total of 40 heavily pretreated patients were enrolled. Best response was observed after a median of four cycles in 77.5%: globally, 47.5% patients obtained a complete response, 64.2% in the elderly subset. The overall response rate was 62.5%. At the latest follow up, 15/18 patients are still in complete remission (3 with consolidation). The progression-free survival rate at 24 months was 39.1% and the disease-free survival rate at the same time was 54% (median not reached). All the long-term responders were aged <30 years at first infusion. The treatment was well tolerated even in this real-life context and no deaths were linked to drug toxicity. Brentuximab vedotin induces clinical responses quite rapidly, i.e. within the first four cycles of treatment in most responders, thus enabling timely use of transplantation. For patients ineligible for transplant or for those in whom a transplant procedure failed, brentuximab vedotin may represent a feasible effective therapeutic option in everyday clinical practice.

Imatinib and polypharmacy in very old patients with chronic myeloid leukemia: effects on response rate, toxicity and outcome.

BACKGROUND: About 40% of all patients with chronic myeloid leukemia are currently old or very old. They are effectively treated with imatinib, even though underrepresented in clinical studies. Furthermore, as it happens in the general population, they often receive multiple drugs for associated chronic illnesses. Aim of this study was to assess whether or not in imatinib-treated patients aged >75 years the exposure to polypharmacy (5 drugs or more) had an impact on cytogenetic and molecular response rates, event-free and overall survival, as well as on hematological or extra-hematological toxicity. METHODS: 296 patients at 35 Italian hematological institutions were evaluated. RESULTS: Polypharmacy was reported in 107 patients (36.1%), and drugs more frequently used were antiplatelets, diuretics, proton pump inhibitors, ACE-inhibitors, beta-blockers, calcium channel blockers, angiotensin II receptors blockers, statins, oral hypoglycemic drugs and alpha blockers. Complete cytogenetic response was obtained in 174 patients (58.8%), 78 (26.4%) within 6 month, 63 (21.3%) between 7 and 12 months. Major molecular response was obtained in 153 patients (51.7%), 64 (21.6%) within the 12 month. One hundred and twenty-eight cases (43.2%) of hematological toxicity were recorded, together with 167 cases (56.4%) of extra-hematological toxicity. Comparing patients exposed to polypharmacy to those without, no difference was observed pertaining to the dosage of imatinib, cytogenetic and molecular responses and hematological and extra-hematological toxicity. CONCLUSION: Notwithstanding the several interactions reported in the literature between imatinib and some of the medications considered herewith, this fact does not seem to have a clinical impact on response rate and outcome.

Italian daily platelet transfusion practice for haematological patients undergoing high dose chemotherapy with or without stem cell transplantation: a survey by the GIMEMA Haemostasis and Thrombosis Working Party.

BACKGROUND: Following high-dose chemotherapy/bone marrow transplantation, patients are routinely, prophylactically transfused with platelet concentrates (PC) if they have a platelet count ≤10×109/L or higher in the presence of risk factors for bleeding. However, whether such transfusions are necessary in clinically stable patients with no bleeding, or whether a therapeutic transfusion strategy could be sufficient and safe, is still debated. MATERIALS AND METHODS: The GIMEMA Haemostasis and Thrombosis Working Party sent a questionnaire to Italian haematology departments to survey several aspects of daily platelet transfusion practice, such as the cut-off platelet count for transfusion, the evaluation of refractoriness and the type of PC administered. RESULTS: The questionnaire was answered by 18 out of 31 centres (58%). A total of 23,162 PC were transfused in 2,396 patients in 2013. The vast majority of centres (95%) transfused PC according to Italian and international guidelines; only a few transfused always at platelet counts ≤20×109/L. The broad agreement on platelet count cut-off for transfusion (≤10×109/L) was not confirmed when the World Health Organization (WHO) bleeding score was considered: only a third of centres (33%) used transfusions as recommended when the bleeding grade was ≥2. Platelet refractoriness was poorly monitored and most centres (89%) evaluated, mostly empirically (67%), response to transfusion only 24 hours later. Thirty percent of centres transfused platelets in asymptomatic refractory patients. DISCUSSION: Although most Italian haematology departments transfuse PC according to Italian and international guidelines, our survey shows that in routine daily practice physicians do not comply closely with the WHO recommendations on platelet transfusions and monitoring platelet refractoriness. This causes excessive platelet transfusions, with a resulting increase of costs and waste of public health resources.

Prospective study of hepatitis B virus reactivation in patients with hematological malignancies.

BACKGROUND AND AIM: The best strategy for managing patients with resolved hepatitis B virus infection (HBsAg negative, anti-HBc antibodies positive with or without anti-HBs antibodies) and hematological malignancies under immunosuppressive therapies has not been defined. The aim of this study was to prospectively analyze the risk of hepatitis B virus reactivation in these patients. MATERIAL AND METHODS: Twenty-three patients (20 positive for anti-HBs) were enrolled. Eleven patients underwent hematopoietic stem cell transplantation (autologous in 7 cases, allogeneic in 4 cases) while the remaining 12 were treated with immunosuppressive regimens (including rituximab in 9 cases). RESULTS: During the study no patient presented acute hepatitis. However, three anti-HBc/anti-HBs positive patients who were treated with allogeneic hematopoietic stem cell transplantation demonstrated hepatitis B virus reactivation within 12 months from transplant. No one of the remaining patients showed hepatitis B virus reverse seroconversion. CONCLUSIONS: Allogeneic hematopoietic stem cell transplantation is a high risk condition for late hepatitis B virus reactivation in patients with resolved infection. Reverse seroconversion seems to be a rare event in anti-HBc/anti-HBs positive patients submitted to autologous hematopoietic stem cell transplantation or systemic chemotherapy with or without rituximab.

Comprehensive geriatric assessment is an essential tool to support treatment decisions in elderly patients with diffuse large B-cell lymphoma: a prospective multicenter evaluation in 173 patients by the Lymphoma Italian Foundation (FIL).

We performed a multicenter study to validate the concept that a simple comprehensive geriatric assessment (CGA) can identify elderly, non-fit patients with diffuse large B-cell lymphoma (DLBCL) in whom curative treatment is not better then palliation, and to analyze potential benefits of treatment modulation after further subdividing the non-fit category by CGA criteria. One hundred and seventy-three patients aged > 69 treated with curative or palliative intent by clinical judgement only were grouped according to CGA into fit (46%), unfit (16%) and frail (38%) categories. Two-year overall survival (OS) was significantly better in fit than in non-fit patients (84% vs. 47%; p < 0.0001). Survival in unfit and frail patients was not significantly different. Curative treatment slightly improved 2-year OS in unfit (75% vs. 45%) but not in frail patients (44% vs. 39%). CGA was confirmed as very efficient in identifying elderly patients with DLBCL who can benefit from a curative approach. Further efforts are needed to better tailor therapies in non-fit patients.

Lenalidomide monotherapy in heavily pretreated patients with non-Hodgkin lymphoma: an Italian observational multicenter retrospective study in daily clinical practice.

Clinical trial results indicate that lenalidomide, an immunomodulatory drug, is a promising treatment in relapsed/refractory non-Hodgkin lymphoma (NHL). This retrospective multicenter study was conducted in patients with relapsed/refractory NHL treated with lenalidomide monotherapy through a Named Patient Program in Italy. Principal endpoints were overall response rate (ORR), safety and overall survival (OS). The ORR in 64 evaluable patients was 42.2% and was similar among patients receiving 10, 15 or 25 mg/day lenalidomide. Response rates in patients with mantle cell, diffuse large B-cell and follicular lymphoma were 45.5%, 42.1% and 20%, respectively. Among patients who responded to most recent prior therapy, ORR was 50.0% versus 36.8% in patients with refractory NHL. Mean duration of response in patients receiving any lenalidomide dose was 10.5 months; 1-year progression-free survival and OS were 50.3% and 82.6%, respectively. These findings suggest that lenalidomide is effective and safe for heavily pretreated patients with NHL in the clinical setting.

Age influences initial dose and compliance to imatinib in chronic myeloid leukemia elderly patients but concomitant comorbidities appear to influence overall and event-free survival.

We applied Charlson comorbidity index (CCI) stratification on a large cohort of chronic myeloid leukemia (CML) very elderly patients (>75 years) treated with imatinib, in order to observe the impact of concomitant diseases on both compliance and outcome. One hundred and eighty-one patients were recruited by 21 Italian centers. There were 95 males and 86 females, median age 78.6 years (range 75-93.6). According to Sokal score, 106 patients were classified as intermediate risk and 55 as high risk (not available in 20 patients). According to CCI stratification, 71 patients had score 0 and 110 a score ≥ 1. Imatinib standard dose was reduced at start of therapy (200-300 mg/day) in 68 patients independently from the evaluation of baseline comorbidities, but based only on physician judgement: 43.6% of these patients had score 0 compared to 34% of patients who had score ≥ 1. Significant differences were found in terms of subsequent dose reduction (39% of patients with score 0 compared to 53% of patients with score ≥ 1) and in terms of drug discontinuation due to toxicity (35% of patients with score 0 vs 65% of patients with score ≥ 1). We did not find significant differences as regards occurrence of hematologic side effects, probably as a consequence of the initial dose reduction: 39% of patients with score 0 experienced grade 3/4 hematologic toxicity (most commonly anemia) compared to 42% of patients with score ≥ 1. Independently from the initial dose, comorbidities again did not have an impact on development of grade 3/4 non-hematologic side effects (most commonly skin rash, muscle cramps and fluid retention): 62% of patients with score 0 compared to 52.5% of patients with score ≥ 1. Notwithstanding the reduced dose and the weight of comorbidities we did not find significant differences but only a trend in terms of efficacy: 66% of patients with score 0 achieved a CCyR compared to 54% of patients with score ≥ 1. Comorbidities appeared to have an impact on median OS (40.8 months for patients with score 0 vs 20.16 months for patients with score ≥ 1) on EFS and on non-CML death rate. Our results suggest that treatment of very elderly CML patients might be influenced by personal physician perception: evaluation at baseline of comorbidities according to CCI should improve initial decision-making in this subset of patients.

Deferasirox for transfusion-dependent patients with myelodysplastic syndromes: safety, efficacy, and beyond (GIMEMA MDS0306 Trial).

BACKGROUND: In the absence of randomized, controlled trial data to support iron chelation therapy in transfusion-dependent patients with myelodysplastic syndromes (MDS), continued evidence from large prospective clinical trials evaluating the efficacy and safety of iron chelation therapy in this patient population is warranted. METHODS: The safety and efficacy of deferasirox was examined in a prospective, open-label, single-arm, multicenter trial of transfusion-dependent patients with International Prognostic Scoring System low- or intermediate-1-risk MDS and evidence of transfusion-related iron overload. The effects of deferasirox therapy on hematological response and disease progression were also examined. RESULTS: Of 159 participants enrolled from 37 Italian centers, 152 received ≥1 dose of deferasirox (initiated at 10-20 mg/kg/day and titrated as appropriate), and 68 completed the study. Of 84 patients who discontinued deferasirox therapy, 22 died during the trial, and 28 withdrew due to an adverse event (AE). Fourteen treatment-related grade 3 AEs occurred in 11 patients, whereas no grade 4 or 5 drug-related AEs were reported. Significant risks for dropout were a higher serum ferritin level at baseline, a higher MDS-Specific Comorbidity Index, and a shorter diagnosis-enrollment interval. Median serum ferritin level fell from 1966 ng/mL to 1475 ng/mL (P < 0.0001). The cumulative incidence of transfusion independence, adjusted for death and disease progression, was 2.6%, 12.3%, and 15.5% after 6, 9, and 12 months, respectively. CONCLUSIONS: Deferasirox therapy in transfusion-dependent patients with MDS was moderately well tolerated and effectively lowered serum ferritin levels. Positive hematological responses were observed, and a subset of patients achieved transfusion independence.

Efficacy and safety of bendamustine for the treatment of patients with recurring Hodgkin lymphoma.

The management of patients with Hodgkin lymphoma (HL) recurring after stem cell transplantation (SCT) and multiply relapsed disease remains challenging. We report on 41 such patients who received bendamustine hydrochloride, a bifunctional mechlorethamine derivative mechanistically unrelated to traditional alkylators, after a median of four prior chemotherapy lines, including SCT in 85% of cases. Bendamustine was given at doses of 90-120 mg/m(2) every 21 or 28 d. At first assessment (2-4 cycles), the overall response rate (ORR) was 78% with 12 (29%) complete (CR) and 20 (49%) partial responses (PR). Upon treatment prolongation to 6-8 courses, 40% of PRs progressed, yielding a final ORR of 58% with 31% of CRs. Eight patients (two CRs, six PRs) were subsequently allotransplanted. Median progression-free and overall survival exceeded 11 and 21 months respectively; complete responders displayed a median disease-free survival above 9 months with a relapse rate of only 30%. Outcomes were independent of disease chemosensitivity, previous transplant and bendamustine dose-intensity. No life-threatening or unexpected adverse events occurred. Within the limits of a retrospective analysis and schedule heterogeneity, these results appear very encouraging and prompt prospective trials to confirm bendamustine as a valuable option in the palliative setting and in cytoreductive strategies before allotransplantation.

Bendamustine with or without rituximab for the treatment of heavily pretreated non-Hodgkin's lymphoma patients : A multicenter retrospective study on behalf of the Italian Lymphoma Foundation (FIL).

Bendamustine is an alkylating agent with a nitrogen mustard group and a purine-like benzimidazole group. The aim of this study was to collect all the Italian experiences with this drug in order to evaluate the results in term of response to therapy and toxicities. We analyzed lymphoma patients treated in 24 Italian haematological centres with bendamustine alone or in combination with anti-CD20 antibody. One hundred seventy-five relapsed or refractory lymphoma patients were enrolled. The median age was 69 years (range 26-87). Seventy-nine patients were relapsed, 35 were refractory and 61 presented a progressive disease after partial response. The diagnoses were 60 indolent non-follicular lymphomas, 34 diffuse large B-cell lymphomas, 48 follicular lymphomas, 30 mantle cell lymphomas and three peripheral T-cell lymphomas. All patients were evaluable for response: 52 (29%) with complete remission, 72 (43%) with partial response with an overall response rate of 71%, and 51 non-responders. With a median observation period of 10 months (1-43), 70% of patients are alive. In summary, this retrospective study shows that treatment with bendamustine alone or in combination with rituximab is a safe and effective regimen in a subset of multi-resistant patients.

An overview on the role of FLT3-tyrosine kinase receptor in acute myeloid leukemia: biology and treatment.

Hematopoiesis, the process by which the hematopoietic stem cells and progenitors differentiate into blood cells of various lineages, involves complex interactions of transcription factors that modulate the expression of downstream genes and mediate proliferation and differentiation signals. Despite the many controls that regulate hematopoiesis, mutations in the regulatory genes capable of promoting leukemogenesis may occur. The FLT3 gene encodes a tyrosine kinase receptor that plays a key role in controlling survival, proliferation and differentiation of hematopoietic cells. Mutations in this gene are critical in causing a deregulation of the delicate balance between cell proliferation and differentiation. In this review, we provide an update on the structure, synthesis and activation of the FLT3 receptor and the subsequent activation of multiple downstream signaling pathways. We also review activating FLT3 mutations that are frequently identified in acute myeloid leukemia, cause activation of more complex downstream signaling pathways and promote leukemogenesis. Finally, FLT3 has emerged as an important target for molecular therapy. We, therefore, report on some recent therapies directed against it.