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Background Low risk Myelodysplastic syndromes (LR MDS) are a heterogeneous group of clonal disorders of the hematopoietic stem cell characterized by ineffective hematopoiesis, peripheral cytopenias and relative increase of bone marrow blasts [List 2004]. The most common cytopenia is anemia, which occurs in 85-90% of cases (isolated in 35% of cases) [Fenaux 2013], and ranges from mild/asymptomatic to transfusion dependent. The standard of care for anemia remains supportive care and about 70% of cases benefits from erythropoiesis-stimulating agents (ESAs). According to the FAB classification, a low-risk group of MDS characterized by the presence of ring sideroblasts (RS) was recognized. In the 2017 WHO classification, the nosologic entities of MDS uni-linear and multi-linear dysplasia with RS (MDS-UD-RS, MDS-MD-RS) were established, to emphasize the importance of identifying forms with a potential therapeutic target [Arber 2016]. Luspatercept is a recombinant fusion protein consisting of the modified extracellular domain of human activin receptor type IIB (ActRIIB) linked to a domain of human immunoglobulin Fc G1. The drug showed efficacy in re-establishing erythropoiesis and was recently approved for the treatment of adult patients with very low- to intermediate-risk MDS-RS failing ESAs[Platzbecker 2017; Fenaux 2020]. Aims To retrospectively assess the efficacy and/or clinical benefit (defined as a reduction in red blood cells transfusions [RBCT] or increase in hemoglobin levels) of luspatercept in patients with LR MDS with RS in a real-life setting. Safety issues were also addressed and clinical and hematological predictors of outcome analyzed. Methods We considered all IPSS-R lower-risk MDS with RS patients with unsatisfactory response or unsuitable for ESAs, treated with luspatercept as monotherapy through an expanded access program since November 2020, in 2 tertiary hematologic centers in Milan, Italy. Luspatercept was administered according to the published schedule: starting dose 1,0 mg/kg every three weeks, with the possibility to increase up to 1,33 mg/kg and 1,75 mg/kg if patients did not reach transfusion independence or decreased transfusion burden after two consecutive infusions. Response to luspatercept was evaluated according to IWG 2018 criteria: Hb increase by > 1.5 g/dL and/or relevant reduction of units of RBC transfusions by an absolute number of at least 4 RBC transfusions/8 wk compared with the pretreatment transfusion number in the previous 8 wk. Results We included a total of 17 pts (70% males, 30% females), with a median age of 68 years (range 45-89). The median follow-up from the start of the Luspatercept was 4 months (range 3-6).According to WHO 2017 we included 13 MLD (76%) and 4 ULD (24%); in all of them SF3B1 mutations was confirmed. Moreover, According to IPSS-R classification: 5 (27%)cases were intermediate and 12 (73%) low risk. All patients received at least three doses of luspatercept. Nine patients (53%) needed a dose escalation to 1,33 mg/kg, and 7 (41%) required the maximal dose of 1,75 mg/kg. Interestingly, not all patients received a dose escalation, and 8 (47%) obtained prolonged efficacy with 1 mg/kg dose. Hemoglobin levels increased in 9 pts (53%): 4 (24%), 3 (18%) and 2 (12%) cases at 1 mg/Kg, 1,33 mg/kg and 1,75 mg/dl, respectively. Medina increase was 1,5 g/dl (range 0,2 - 2,2) and these levels were maintained for a median of 4 months (range 3-6). In addition, considering transfusion burden, the independence was reached in 3 pts (18%), after a median time of 6 weeks from treatment start. Importantly, off the 14 patients remaining transfusion-dependent, 6 (35%) reduced the transfusion burden. The most prominent toxicity was increased blood pressure (grade 2) occurring in 3 pts (18%), and dizziness (grade 2) in 2 pts (12%); though the drug was generally well tolerated. No serious adverse events (SAEs) were reported. Therefore, patients were treated as outpatients in all cases. At the last follow up, all patients are alive and free from leukemic evolution. Conclusions: Our real-world experience confirms the efficacy of luspatercept in improving erythropoiesis and decreasing transfusion dependency in very low, low or intermediate risk MDS with RS, with an acceptable toxicity profile. Disclosures Fattizzo: Amgen: Honoraria, Speakers Bureau; Apellis: Speakers Bureau; Annexon: Consultancy; Momenta: Honoraria, Speakers Bureau; Novartis: Speakers Bureau; Alexion: Speakers Bureau; Kira: Speakers Bureau. Barcellini: Agios: Honoraria, Research Funding; Bioverativ: Membership on an entity's Board of Directors or advisory committees; Incyte: Membership on an entity's Board of Directors or advisory committees; Alexion Pharmaceuticals: Honoraria; Novartis: Honoraria.

Background: The treatment for relapsed or refractory acute myeloid leukemia (R/R AML) has minimal chances and a low impact on improving survival. One of the most important goal is to treat unfit patients who are often intolerant to intensive chemotherapy and are not eligible for allogeneic stem cell transplantation. Most patients with AML, including nearly all patients older than 60 years, present multiple, sequentially acquired, somatic mutations. Isocitrate dehydrogenase 2 (IDH2) mutations are present in approximately 8-19% of cases (Buege MJ, Cancers 2018). IDH2 mutations occur early in the leukemogenesis and accumulate an oncogenic product (R-2-hydroxyglutarate) that arrests the histone demethylation pathway, thereby stopping haematopoietic differentiation (Rakheja D, Hum Pathol. 2012). Enasidenib (ENA) is a selective, powerful oral inhibitor of the oncogenic activity of the IDH2 mutant enzyme, that decreases R-2-hydroxyglutarate levels in vitro and in vivo. Interestingly, phase I/II trials showed an overall response rate (ORR) of 40.3% in R/R disease, with 19.3% of complete remission (CR) and with 6.8 % of CR with incomplete haematological recovery (CRi). Moreover, the reported median overall survival was 9.3 months, with 19.7 months (mo) for patients who achieved CR (Stein E, Blood 2017). Aims: To study retrospectively the efficacy and safety of ENA, as single agent, in improving overall survival (OS) and progression-free survival (PFS) in IDH2 mutated R/R AML patients (pts), unfit for intensive chemotherapy. Furthermore, to compare outcomes with a cohort of patients with R/R AML IDH2 wild-type (wt). Methods: Since 2018 we have retrospectively collected and analyzed data of unfit IDH2 mutated R/R AML patients, treated with ENA, thanks to the expanded access program of this drug. The dose was 100 mg/day for all pts. PFS and OS were estimated using the Kaplan-Meier product limit method. Therefore, we considered, as historical comparison, a sample of 28 pts with R/R IDH2 wt AML, treated with the best available therapy at our Institution in the same time frame and matched for clinical features. OS and PFS were compared using the log-rank test. Results: Nine IDH2 mutated pts were considered for analysis: 4 (44%) cases were de novo AML, while 5 (56%) were secondary (1 myelodysplasia and 4 myeloproliferative neoplasms). Median age at relapse was 71 years (range 47-79). Median number of previous therapies was 2 (range 1-3). All pts completed at least one cycle of ENA with a median number of 5 cycles (range 1-16). Median OS from AML diagnosis and from the beginning of ENA was 28 mo (range 3-65), and 15 mo (range 1-27) respectively; median PFS was 13 mo (range 1-14). Among the 28 patients of the control group, with a median age at relapse of 74 years (range 65-86) we recorded a median OS of 14 mo (range 7-62) and an OS from the last relapse of 2 mo (range 0,5-26). The ENA pts group showed a significantly better OS than the control population (p = 0,0419) (Figure 1). The most prominent toxicities were hyperbilirubinemia in 2 pts (22,2%) and IDH-differentiation syndrome (IDH-DS) in 3 (33,3%); though the drug was generally well tolerated. Therefore, patients were treated as outpatients in most cases. Conclusions: In the era of precision medicine, molecular target therapy is the most promising strategy to increase the probability of treatment success with limited side effects. Our experience confirms the efficacy of the IDH2 inhibitor ENA to treat unfit patients with R/R AML in the real life, showing significantly better outcome in terms of survival for the pts treated with target therapy, compared to pts treated with standard therapy. Disclosures Veronese: Janssen Cilag:Honoraria;Bayer:Honoraria;Novartis:Other: Travel Expenses;AstraZeneca:Other: Travel Expenses.

The knowledge of Langerhans Cell Histiocytosis (LCH) is based on pediatric studies. Adults with LCH are usually treated with pediatric protocols. In 2001, guidelines for adults with LCH (GIMEMA LCH 2001) were proposed, in order to standardize the diagnostic and therapeutic approaches for this category of patients. The aims of this retrospective study are: a) to evaluate the role of a multidisciplinary assessment in adults with LCH, according to the GIMEMA LCH 2001 guidelines, and b) to analyze the results obtained with the GIMEMA LCH 2001 guidelines and those obtained with pediatric protocols. Pts aged >18 years with a diagnosis of LCH (S-100+, CD1a+, CD207+) managed at our Institution since 1985 to 2018 were considered. As diagnostic and treatment approaches, two different strategies were used over time: the GIMEMA LCH 2001 guidelines and the pediatric protocols. The GIMEMA LCH 2001 guidelines included a multidisciplinary diagnostic work-up with complete odontostomatologic, pulmonary and endocrinologic assessments; treatment strategy consisted of: wait and see or local therapy in unifocal single system (SS), indomethacin in bone multifocal SS and vinblastine combined with low-dose prednisone (PDN) in multi-system (MS), PDN in pulmonary honey-combing disease (PHCD) and cladribine in central nervous system involvement. DAL-HX 83 and 90, LCH-I and LCH II were the pediatric protocols utilized over time. Response to treatment was defined as complete (CR) or intermediate (IR). Persistence of the symptoms and/or appearance of new lesions were defined no response (NR). Progression was considered the appearance of symptoms and/or new lesions after initial response. One-hundred-thirty-one LCH pts (females 72, males 59) with a median age at diagnosis of 36 years (range 18 - 71) were considered. Median follow up was 43 months (range 12 - 330). One-hundred-seven patients were managed according to the GIMEMA LCH 2001 guidelines, 16 of them previously treated with a pediatric protocol. Pulmonary and/or oral involvements were identified in 31/107 (29%) and 12/107 (11%) patients, respectively, 5/16 (31%) and 3/16 (19%), respectively, of previously treated asymptomatic patients. Ninety-one newly diagnosed patients (median age at diagnosis: 36 years) were treated according to the GIMEMA LCH 2001 guidelines and 40 (median age at diagnosis: 33 years) were managed with pediatric protocols. All patients treated with the GIMEMA LCH 2001 were evaluable for response. In particular, all patients with SS-LCH achieved a response (100%), that was complete in 20/26 (76.9%) unifocal-SS and in 10/14 (71.4%) multifocal-SS. All but one patient with MS-LCH reached a response that was complete in 22/45 (48.9%). Of 6 pts with PHCD, 5 had a IR and one a CR. No pt presented CNS involvement at initial diagnosis. Thirty-nine of 40 pts managed with pediatric protocols were evaluable for response. All 13 pts with SS-LCH had a response that was complete in 6 (46.1%). Among 26 patients with MS-LCH, 3 of them with organ risk involvement achieved a response, that was complete in 1, while among 23 patients without organ risk, 12 (52.2%), 8 (34.8%) and 3 (13%) had a CR, IR and NR, respectively. Overall, 12 patients were lost to follow-up. Disease progression was recorded in 47/95 pts (49.5%) after a median time of 19 months (range: 6-147 months). The progression-free survival at 43 months was significantly better for patients treated according to the GIMEMA LCH 2001 guidelines compared to those managed with pediatric protocols, 67% (IC95% 53.14 - 80.86%) vs 48% (IC95% 31.37 - 64.63%), respectively (p 0.005). Overall, 7 deaths were recorded, 5 in patients treated with the pediatric protocols. The overall survival at 43 months, was similar in patients managed with the GIMEMA LCH 2001 guidelines and in those treated with pediatric protocols (97.9%, CI 95%: 93.75% - 100% and 97.3%, (IC95% 91.96% - 100%). BRAF V600E mutation was found in 13/35 (37%) evaluable cases. No differences in response and outcome between BRAFV600E-mutated patients and those not-mutated were found. Our experience in a large cohort of LCH adults shows that a multidisciplinary approach is useful in identifying organ involvement in adults, including those asymptomatic. This is critical for an adequate treatment. Moreover, guidelines specific for adults with LCH proved efficacy in improving the outcome in this category of patients. Disclosures No relevant conflicts of interest to declare.

Imatinib mesylate (IM) has demonstrated to be highly effective in children with chronic myeloid leukemia (CML). The main issues remain the long-term side effects in pre-pubertal children and the poor compliance in adolescents. The aims of this study were: a) to evaluate the feasibility and efficacy of IM given intermittently to molecular responder (MR) CML children in chronic phase (CP), b) to reduce the long-term side effects of MR patients (pts) who started IM in pre-pubertal age, c) to improve compliance of poorly compliant adolescents in major MR (MMR). Among CP-CML pts aged Fifteen of 58 CP-CML pts diagnosed between March 2001 and June 2015 received IM given intermittently for a median of 40 months(range: 14-86). Before starting int-IM, 5 pts had been in persistent MR4.5-MR5 for a median of 39 months (Group I), 4 pts had been in MR for a median of 28.5 months and had been suffering from long-term side effects (Group II), and 6 pts had been in MMR and were poorly compliant to treatment (Group III). Features and outcome of the 15 pts are shown in Table 1. Group I: 3/5 pts in MR4.5-MR5 discontinued int-IM after 16, 34 and 36 months and remain in continuous MR after 89, 90 and 107 months; 2 pts are still receiving int-IM for 14 and 36 months, respectively. Group II: 2/4 pts achieved a deeper MR (1 from MR4 to MR4.5 and 1 from MR4.5 to MR5) while on int-IM. However, 3 pts lost the response after 24 (cytogenetic relapse), 40 and 77 (molecular) months from the beginning of int-IM; all of them were successfully treated with IM given continuously. One pt is still receiving int-IM. Group III: 2/6 pts achieved a deeper MR (1 from MR3 to MR4.5 and 1 from MR3 to MR4) while on int-IM. However, 5/6 patients lost their response after a median time of 69 months (57-74). Four of them were treated with IM given continuously and 1 received dasatinib; all obtained a response. One, who achieved a deeper MR (MR3 to MR4), is still on int-IM after 86 months. Overall, 4/15 (26.7%) pts improved their molecular response while on int-IM and 3/15 pts (20%) successfully discontinued treatment. On the other hand, 8/15 pts (53.3%) failed int-IM after a median of 63 months (range 24-77) from the beginning (6 pts lost MMR and 2 pts had a cytogenetic relapse). No pt underwent a stem cell transplantation. Long-term side effects (bone metabolism, growth rate and pubertal development) progressively improved during IM given intermittently. At the last follow-up, 6 pts (4 MR5, 1 MR4.5, 1 MR3) are still receiving int-IM, 5 (3 MR4, 2 MR2) are receiving continuous IM, 3 (MR4.5-MR5) are treatment-free and 1 (MR3) is being treated with dasatinib. All patients are alive at a median time from diagnosis of 151 months (range 52-266). Our experience suggests that an intermittent schedule of IM given 3 weeks a month could be an effective strategy before stopping IM in CP-CML children in persistent deep MR. Moreover, this approach is capable of improving the molecular response in poor compliant pts and is useful to reduce IM-related long-term side effects. The relatively high number of relapses in group III (5/6, 83%) is indicative of its poor efficacy in pts not compliant to IM given continuously. Based on these data, a prospective cooperative study has been planned. Disclosures Malaspina: Sapienza University, Rome: Other: Resident in Hematology. Rizzo:Sapienza University, Rome: Other: Resident in Hematology. Locatelli:bluebird bio: Consultancy; Bellicum: Consultancy, Membership on an entity's Board of Directors or advisory committees; Novartis: Consultancy, Membership on an entity's Board of Directors or advisory committees; Miltenyi: Honoraria; Amgen: Honoraria, Membership on an entity's Board of Directors or advisory committees. Foà:CELGENE: Other: ADVISORY BOARD, Speakers Bureau; AMGEN: Other: ADVISORY BOARD; CELTRION: Other: ADVISORY BOARD; GILEAD: Speakers Bureau; NOVARTIS: Speakers Bureau; JANSSEN: Other: ADVISORY BOARD, Speakers Bureau; INCYTE: Other: ADVISORY BOARD; ABBVIE: Other: ADVISORY BOARD, Speakers Bureau; ROCHE: Other: ADVISORY BOARD, Speakers Bureau.

BACKGROUND In allogeneic hematopoietic stem cell (HSC) transplantation, the collection of an appropriate number of HSCs while maintaining a high level of safety for healthy donors is fundamental. Inadequate HSC mobilization can be seen with the standard use of granulocyte–colony-stimulating (G-CSF). Plerixafor (PL) is a chemokine receptor CXC Type 4–stromal-derived factor 1 inhibitor; its HSC-mobilizing properties are synergistic with G-CSF in poor mobilizing patients. The use of PL as adjuvant or alternative to G-CSF in healthy donors has shown a good safety profile but is so far off-label. STUDY DESIGN AND METHODS We report 10 healthy HSC donors treated with PL because of insufficient response to G-CSF alone or contraindication to G-CSF. Eight donors did not mobilize enough CD34+ cells with G-CSF alone because poor mobilizers or because insufficient HSCs were harvested according to the clinical need of the patient; in two cases G-CSF administration and marrow harvest were unfeasible or contraindicated in the donor. RESULTS The use of PL for mobilization increased the number of circulating CD34+ cells by 2.8-fold and the CD34+/kg collection by 3.0-fold. Only mild adverse events were reported (bone pain or discomfort) and not univocally attributable to PL. Rate of engraftment and graft-versus-host disease were similar to those seen in recipients of grafts from G-CSF only–mobilized donors. CONCLUSION We exposed 10 allogeneic donors to mobilization with PL. PL was well tolerated in all cases and ensured procurement of an adequate graft for transplantation resulting in a normal hematopoietic engraftment.

Background. Imatinib, the first BCR/ABL kinase inhibitor, has drastically changed the chronic myeloid leukemia (CML) scenario improving the rate of responses and long-term outcome. The aim of our analysis was to assess, after a median follow-up of 10.2 years (range 5.8-14.8), the long-term efficacy and safety of imatinib treatment in a monocentric cohort of CML patients treated outside of clinical trials. Methods. We retrospectively analyzed a series of 458 CML patients treated with imatinib frontline or after interferon (IFN) failure at a single center between 2000 and 2016. Long-term analysis included overall survival (OS), progression-free survival (PFS), event-free survival (EFS), response to treatment and adverse events. Results. The median age was 55.1 years (range 18.8-91.2). Seventy-one % of patients received imatinib frontline and 29% after IFN failure. Median time of prior IFN treatment was 5.6 years (range 2.4-8.9); the 10-year OS of patients treated with imatinib after IFN and with imatinib frontline was 75.3% (CI 95%: 66.9-81.9) and 77.8% (CI 95%: 72.2-82.5) (p=0.468), respectively. The 10-year-OS of the whole cohort was 77.1% (CI 95%: 73.1-81.5); the 10-year probability of dying due to CML and of other causes was 7.8% (CI 95%: 5.1-10.3) and 16% (CI 95%: 11.5-18.8), respectively (Figure 1). When patients were stratified into 4 groups according to age (18-35, >35-50-65 years), no difference was found in the 10-year OS considering only the CML-related deaths (p=0.472), whereas a difference was observed when all other causes of death were considered (p Conclusions. A 10-year real-life follow-up of CML patients demonstrates that imatinib maintains efficacy over time and is associated with a low rate of CV events and second neoplasias. Disclosures Rizzo: Sapienza University, Rome: Other: Resident in Hematology. Foà:GILEAD: Speakers Bureau; INCYTE: Other: ADVISORY BOARD; AMGEN: Other: ADVISORY BOARD; ABBVIE: Other: ADVISORY BOARD, Speakers Bureau; CELTRION: Other: ADVISORY BOARD; NOVARTIS: Speakers Bureau; JANSSEN: Other: ADVISORY BOARD, Speakers Bureau; CELGENE: Other: ADVISORY BOARD, Speakers Bureau; ROCHE: Other: ADVISORY BOARD, Speakers Bureau. Breccia:Novartis: Honoraria; BMS: Honoraria; Incyte: Honoraria; Pfizer: Honoraria.

Background. 5-Azacitidine (5-AZA) had changed the therapeutic approach to intermediate-2/high IPSS risk myelodysplastic syndromes (MDS) improving the outcome of patients, even in the absence of a complete response. However, real-life experiences have reported contradicting results compared to the AZA001 randomized study. Aim of our analysis was to identify the clinico-biological features at baseline and during treatment associated with the overall survival (OS) and progression-free survival (PFS) at two years in a consecutive cohort of patients treated with hypometylating agent in the clinical practice. Moreover, we propose a new prognostic score for the identification of OS after the first four cycles of therapy. Patients and Method. We retrospectively analyzed a series of 110 MDS patients treated at a single institution with 5-AZA between September 2003 and January 2017. Patients were diagnosed according to the WHO 2016 criteria. 5-AZA was administered at a dose of 75 mg/m2 according to the 5+2+2 schedule every 28 days. Results. A male predominance was observed (male/female: 66%/34%) with a median age of 70 years (range 38-85). The median dose of 5-AZA received was 135 mg/day (range 105-150) after a median time from diagnosis of 2.3 months (range 0.1-119). Median duration of therapy was 9.5 cycles (range 1-77) with a median time on treatment of 8.5 months (range 1-86.7). OS of the whole cohort was 66.1% (CI 95% 57.2-76.4) at 1 year and 38.3% (CI 95% 29.4-49.9) at 2 years. Seventy-seven patients (70%) performed four cycles of therapy. According to the IWG criteria, 42 patients (54.5%) achieved a complete remission (CR), 11 (14.2%) a partial remission (PR), 17 (22.4%) maintained a stable disease (SD), 2 (2.5%) and 5 (6.4%) presented a progression disease (PD) and a failure, respectively. The 2-year OS was 68% in patients who obtained a CR/PR, 20% in patients with SD and 16% in patients with PD/failure (p75 years, p=0.075). The baseline bone marrow blasts percentage did not impact on OS and PFS (OS, p=0.867; PFS, p=0.611). According to the Revised International Prognostic Score (R-IPSS), 22 (20%), 46 (42.8%) and 42 (38.2%) patients were classified as intermediate, high and very high-risk patients, respectively. We identified that the very high-risk group had an inferior 2-year OS (17%) compared to intermediate-group patients (64%, p10% identified patients with a worse outcome, with a 2-year OS of 9.4% compared to 60.3% for patients with 0-5% blasts and 44.7% for patients with 5-10% blasts (p=0.002). The occurrence of one infection during the first four cycles impacted on the 2-year OS (31.6% vs 58.3% in patients without, p=0.032). We applied a dynamic prognostic score according to age, cytogenetic risk, transfusion need, number of 5-AZA cycles performed and type of response after the fourth cycle (Table 1): the combination of these variables identified 3 categories of risk with a significantly different 2-year OS: low-risk (72.3%), intermediate (19.8%) and high-risk (8.9%) (p Conclusions. Our results in a large and consecutive MDS cohort treated outside of clinical trials defined prognostic factors, such as transfusion dependency, persistence of >10% blasts after four cycles and absence of infections, capable of identifying patients with a good outcome. A prognostic score is proposed that requires independent validations in similar cohorts of patients. Disclosures Rizzo: Sapienza University, Rome: Other: Resident in Hematology. Foà:NOVARTIS: Speakers Bureau; CELTRION: Other: ADVISORY BOARD; GILEAD: Speakers Bureau; JANSSEN: Other: ADVISORY BOARD, Speakers Bureau; ROCHE: Other: ADVISORY BOARD, Speakers Bureau; CELGENE: Other: ADVISORY BOARD, Speakers Bureau; AMGEN: Other: ADVISORY BOARD; ABBVIE: Other: ADVISORY BOARD, Speakers Bureau; INCYTE: Other: ADVISORY BOARD. Breccia:Pfizer: Honoraria; Novartis: Honoraria; BMS: Honoraria; Incyte: Honoraria.

Background: the Registro Italiano Trombocitemie (RIT) was activated mainly to evaluate the diagnosis and therapy appropriateness in the thrombocythemic patients with Ph-negative myeloproliferative neoplasm (MPN) observed in the adhering centers. Objective: to evaluate how the diagnostic and therapeutic approach changed in the RIT patients diagnosed with thrombocythemic MPN in the last two decades. Methods: the RIT centers registered by a web-based system during the years 2005-2014 their thrombocythemic MPN patients, and semesterly updated their follow-up data. For patients diagnosed before 2005, the data on diagnosis and prior follow-up were retrospectively collected. The diagnostic process and the initial treatment (started into the first year after diagnosis) were comparatively analyzed in the patients diagnosed before and after 2005. Results: the RIT centers registered 2629 patients. 2388 of them, object of this analysis, were diagnosed between1995 and 2014: 1098 (46%) in the decade 1995-2004 (Group I), and 1290 (54%) in the decade 2005-2014 (Group II). The diagnostic process in the patients of Group II and Group I included bone marrow biopsy (BMB, performed into 1 year and before any cytoreduction): 85% vs 80%, p The patients of Group II, as compared with those of Group I, showed a similar gender distribution (M/F ratio 0.61 vs 0.65, p 0.452), and had at diagnosis: a higher age (median 60 vs 57 years, p 60 years in 50% vs 45% of cases, p Moreover, they had: a lower platelet (PLT) count (median 737 vs 775 x 109/L, p 10 x 109/L in 28% vs 26% cases); a similar median levels of hematocrit (HCT %, in females 41.4 vs 41.0; in males 44.7 vs 44.6) and hemoglobin (Hb g/dL, in females 13.8 vs 13.6; in males 15.0 vs 14.9). The BMB, revised according to the WHO 2008 criteria, showed a not different distribution (p 0.21) of ET (64% vs 61%), ep-PMF (16% vs 17%), PMF (3% vs 2%), PV (4% vs 4%), and U-MPN (13% vs 16%. The JAK2 V617F mutation in patients of Group II (at diagnosis) and of Group I (after diagnosis) was found in 62% and in 58% of tested cases (p 0.054), respectively. The patients at high standard thrombotic risk were 58% vs 52%, p 0.004. In the patients of Group II and Group I the distribution of the treatment started into the first year was significantly different (p The treatment CYT ± AntiPLT was started in the patients at high standard thrombotic risk with a rate of 81% vs 80%, respectively, and in the patients at low standard thrombotic risk in 37% vs 43% of cases, respectively. The initial treatment CYT±AntiPLT was related, in multivariate analysis, both in patients of Group II and Group I, with older age (>60 and 40-60 vs 1000 and 700-1000 vs Conclusion: in the studied thrombocythemic MPN patients the real-life diagnostic approach was improved after 2005 not only due to the routine use of JAK2 tests, but also due to the higher rate of BMB done (85% vs 80%). The appropriateness of the cytoreductive treatment (CYT±AntiPLT started into one year from diagnosis) remained high in patients at high standard thrombotic risk (over 80% of cases were treated). Concomitantly, the inappropriate use of the cytoreductive drugs in patients at low standard thrombotic risk appreciably decreased (from 43% to 37% of cases). Moreover, it has to be remarked that the therapeutic approach was significantly influenced not only by older age and prior thrombosis, but also by thrombocytosis (PLT count >700 x 109/L), disease-related symptoms, and inconstantly by leukocytosis and CVRFs. Table Table. Disclosures Gugliotta: SHIRE Co.: Honoraria. Gugliotta:Bristol Myers Squibb: Consultancy, Honoraria; Novartis: Consultancy, Honoraria.