Acute myeloid leukemia (AML) is a heterogeneous hematologic malignancy, and 5%-20% of newly diagnosed patients present with hyperleukocytosis (HL). HL, most often defined as WBC > 100 000/μL, is a hematologic emergency associated with severe complications, early mortality, and poor prognosis, requiring immediate intervention. From November 2005 to September 2025, 65 newly diagnosed AML patients with HL underwent leukocytapheresis (LCP) at University Hospital Olomouc. Clinical data were retrospectively collected from medical records. The primary objective was to evaluate the procedural efficacy and safety. Clinical and laboratory data were analyzed. Survival outcomes were assessed by Kaplan-Meier analysis and compared using the log-rank test. Median age at diagnosis was 57 years. Dyspnea (60.0%), neuropsychiatric symptoms (31.7%), and visual impairment (6.2%) were the most common leukostasis manifestations. LCP effectively reduced WBC counts without significant adverse events, median of 2.2 TBV was treated, and 52.3% of the patients requiring more than one session. FLT3-ITD and NPM1 mutations were detected in 26/46 (56.5%) and 17/43 (39.5%), respectively, KMT2A rearrangements were present in 5/57 (8.8%). Intensive chemotherapy was feasible in 56.9% of patients, with 26.2% undergoing allo-HSCT. Median OS was 5.9 months (95% CI: 1.3-8.4), significantly longer in therapy-eligible patients, but outcomes remained poor, highlighting HL as an unmet clinical need. LCP remains a valuable therapeutic option for patients with HL in newly diagnosed AML. Our long-term experience supports its safety and efficacy, particularly in symptomatic patients, as a bridge to definitive therapy regardless of treatment intensity eligibility.

Currently there is no established prognostic scoring system for patients with chronic myeloid leukemia (CML) in blast phase (BP). This study aimed to identify prognostic factors of CML-BP in a large cohort of prospectively and retrospectively collected patients and to develop a readily available prognostic scoring system at the onset of BP to enable future comparison between different trials and series. The analyses were based on 275 patients from thirteen countries, collected within the European LeukemiaNet Blast Phase Registry with a median observation time of 45 months and a median OS of 18.9 months. A Cox proportional hazards model for overall survival (OS) was employed, missing values were imputed. The study identified six independent prognostic factors: blast percentage, platelet count, age (all at onset of CML-BP), immunophenotype of BP, extramedullary disease, and previous history of CML. The low-risk group, encompassing 14% of patients, had a median OS of 97 months, the intermediate-risk group (59% of patients) of 22 months, and the high-risk group (27% of patients) of 9 months. Cross-validation demonstrated a good performance of the score, although external validation is strongly recommended. Despite the inherent limitations of registry data, the findings offer robust insights into prognostic factors for CML-BP.

The influence of t(v;22) sole, major route ACAs all (+8, n = 14; +Ph, n = 10; +19, n = 1), and -Y sole on progression-free survival. Survival curves are compared with those of patients with the standard t(9;22) translocation. Other ACAs or complex karyotypes did not influence survival.

Background: In chronic myeloid leukemia (CML), DNA-based measurable residual disease (MRD) analysis—either combined with RNA MRD (Machova Polakova et al. Leukemia 2020) or with characterization of DNA-positive cell subtypes (Pagani et al. Blood 2023)—has demonstrated predictive value for treatment-free remission (TFR). These strategies form the basis of the TFR traffic light stratification model, previously described in patients undergoing direct tyrosine kinase inhibitor (TKI) cessation. Aim: This study evaluated the applicability of the DNA-/RNA-based TFR traffic light model in a structured, two-step TKI dose de-escalation protocol prior to cessation, as implemented in the HALF trial (NCT04147533). Methods: Between 2020 and 2023, 95 of 207 patients enrolled in the HALF trial underwent genomic breakpoint characterization and optimization of BCR::ABL1 DNA digital PCR assays. To date, DNA and RNA MRD assessments were performed in 83 patients, generating 1,222 paired samples. MRD was monitored throughout the two de-escalation phases: (1) halving the TKI dose for six months, followed by (2) alternate-day dosing for an additional six months. Patients maintaining major molecular response (MMR) proceeded to TKI cessation. Results: At the end of phase 1, 83 patients were stratified as follows: 29 double-negative (green), 26 DNA⁺/RNA⁻ (yellow), and 28 double-positive (red). After phase 2, MRD status shifted to 31 green, 19 yellow, and 33 red. Only red-group patients relapsed during phase 2 (n = 7). By 24 months post-enrolment, MRD dynamics continued to evolve. In the yellow group, 11/19 progressed to double-positive (4 relapsed); 1 reverted to green. Among green patients, 6 converted to red (3 relapsed), and 2 to yellow. In the red group, 11 remained unchanged; 14 relapsed; and 1 improved to yellow. Stratification by MRD status at 12 months significantly predicted molecular recurrence-free survival (MRFS) at 18 months (i.e., 6 months post-TKI cessation): red group, 39% MRFS (HR: 9.71; 95% CI: 2.87–32.78; p = 0.00025); yellow group, 87% MRFS (HR: 1.68; 95% CI: 0.34–8.34; p = 0.56); green group, 90% MRFS. This stratification remained consistent at 36 months (i.e., 24 months post-TKI cessation): red group, 36% MRFS (HR: 8.10; 95% CI: 2.77–23.69; p = 0.00013); yellow group, 74% MRFS (HR: 2.12; 95% CI: 0.57–7.91; p = 0.26); green group, 87% MRFS. Conclusion: Persistent RNA positivity (double-positive MRD) is significantly associated with molecular relapse both during phase 2 of TKI dose reduction and after TKI cessation. DNA MRD analysis is essential to distinguish truly MRD-negative (green) patients from those with DNA⁺/RNA⁻ status (yellow), who carry an intermediate risk of relapse. Importantly, in yellow-group patients, the emergence of RNA expression during either phase of dose reduction indicates an increased risk of relapse. In such cases, we recommend returning to the previous TKI dose rather than proceeding to cessation. For green-group patients, the appearance of DNA positivity should prompt close monitoring, and any subsequent RNA positivity should be considered a warning sign to resume reduced-dose or full-dose TKI therapy. Overall, the two-step TKI de-escalation strategy, when combined with integrated DNA/RNA MRD monitoring in RNA-negative patients through regular follow-up, may reduce the risk of molecular relapse and improve patient selection for safe TKI discontinuation. Supported by Ministry of Health of the Czech Republic NU22-03-00136, MH CZ – DRO (IHBT 0002373), National Institute for Cancer Research Project (Programme EXCELES, ID Project No. LX22NPO5102) - Funded by the EuropeanUnion - Next Generation EU

Blast phase (BP) of chronic myeloid leukemia (CML) still represents an unmet clinical need with a dismal prognosis. Due to the rarity of the condition and the heterogeneity of the biology and clinical presentation, prospective trials and concise treatment recommendations are lacking. Here we present the analysis of the European LeukemiaNet Blast Phase Registry, an international collection of the clinical presentation, treatment and outcome of blast phases which had been diagnosed in CML patients after 2015. Data reveal the expected heterogeneity of the entity, lacking a clear treatment standard. Outcomes remain dismal, with a median overall survival of 23.8 months (median follow up 27.8 months). Allogeneic stem cell transplantation (alloSCT) increases the rate of deep molecular responses. De novo BP and BP evolving from a previous CML do show slightly different features, suggesting a different biology between the two entities. Data show that outside clinical trials and in a real-world setting treatment of blast phase is individualized according to disease- and patient-related characteristics, with the aim of blast clearance prior to allogeneic stem cell transplantation. AlloSCT should be offered to all patients eligible for this procedure.

Overall survival of patients classified according to the European LeukemiaNet 2020 classification. Chronic phase (CP), accelerated phase (AP), blast crisis (BC), low risk (LR), intermediate risk (IR), high risk (HR).

Blood basophils ≥ 20 percent is reportedly associated with a poor prognosis and used to define accelerated phase of chronic myeloid leukaemia (CML) in some classifications. However, quantification of blood basophils is by percentage is inaccurate. Using a Patient Similarity Network (PSM) approach we identified basophil concentration rather than percentage as the more accurate predictive co-variate. To test this observation we interrogated data for a possible correlation between blood basophils quantified by concentration in a training cohort of 131 subjects with newly-diagnosed chronic phase CML receiving tyrosine kinase-inhibitor (TKI)-therapy. Subjects with a basophil concentration ≥ 12.2 x 10E + 9/L had poorer event-free survival (EFS, Odds Ratio [OR] = 12.3 [95% Confidence Interval [CI]. 4.2, 36.1]; p < 0.0001) and failure-free survival (FFS; OR = 10.4 [3.89, 27.72]; p < 0.0001). TKI switch-free survival and progression-free survival were also correlated with basophil concentration. The negative impact of a high basophil concentration was validated in an independent cohort of 1,870 subjects. We explain why basophil concentration is a more accurate co-variate. Our data indicate blood basophil concentration at diagnosis rather than percentage is a more accurate predictor of outcomes in persons with newly-diagnosed chronic phase CML receiving TKI-therapy.

AbstractBackgroundTo evaluate the outcomes of first‐line imatinib versus nilotinib treatment for chronic myeloid leukemia in the chronic phase (CML‐CP) in real‐world clinical practice.MethodsA propensity score analysis was performed to eliminate imbalances between the treatment groups. In the analysis, 163 patients in the nilotinib group and 163 patients in the matched imatinib group were retrospectively evaluated.ResultsNilotinib‐treated patients achieved complete cytogenetic response (CCyR) and major molecular response more rapidly than imatinib‐treated patients. However, there was no significant difference in 5‐year overall survival (OS) or progression‐free survival (PFS) between the two groups (OS: 94.3% vs. 90.5%, p = 0.602; PFS: 92.9% vs. 88.0%, p = 0.614). Nilotinib‐treated patients had a higher failure‐free survival (FFS) and event‐free survival (EFS) than imatinib‐treated patients (FFS: 71.7% vs. 54.3%, p = 0.040; EFS: 71.7% vs. 53.5%, p = 0.025).ConclusionsThis retrospective analysis from clinical practice did not confirm any benefit of frontline nilotinib treatment for OS and PFS; however, it did demonstrate higher FFS and EFS in the nilotinib cohort.

Background A lower dosage of tyrosine kinase inhibitors (TKIs) in patients with chronic myeloid leukaemia (CML) has shown efficacy in managing short-term toxicity and maintaining a deep molecular response in patients who fail to achieve treatment-free remission. Method From over 700 patients with CML who were treated at two centres over the last three decades, this retrospective study identified eight patients characterised by long-term treatment failure and simultaneous prolonged significant haematologic toxicity that prevented the use of the standard tyrosine kinase inhibitor dosage. Results Patients had a high or intermediate ELTS risk score, and most had significant comorbidities. Two patients were treated previously with busulfan, and four were aged over 70, which might explain the reduced pool of normal haematopoietic stem cells. However, concomitant myelodysplastic syndrome or the presence of clonal haematopoiesis of indeterminate potential was not demonstrated. Despite prolonged treatment failure, the survival of these patients (who were ineligible for stem cell transplantation) ranged from 45-396 months. Neither mutations in the ABL kinase domain nor additional cytogenetic abnormalities developed during the treatment of these patients, prompting speculation about the low selective pressure of low-dose tyrosine kinase inhibitors and/or the absence of mutations at diagnosis. Conclusion It is important not to stop treatment with tyrosine kinase inhibitors at a low personalised dosage in CML patients with prolonged significant haematologic toxicity despite long-term treatment failure.

Limited data is available on the health-related quality of life (HRQoL) and symptoms of patients with chronic myeloid leukemia (CML) who are in treatment-free remission (TFR). We herein report HRQoL results from the EURO-SKI trial. Patients who had been on tyrosine kinase inhibitors (TKIs) therapy for at least 3 years and achieved MR4 for at least 1 year were enrolled from 11 European countries, and the EORTC QLQ-C30 and the FACIT-Fatigue questionnaires were used to assess HRQoL and fatigue respectively. Patients were categorized into the following age groups: 18-39, 40-59, 60-69 and ≥70 years. Of 728 patients evaluated at baseline, 686 (94%) completed HRQoL assessments. The median age at TKI discontinuation was 60 years. Our findings indicate that HRQoL and symptom trajectories may vary depending on specific age groups, with younger patients benefiting the most. Improvements in patients aged 60 years or older were marginal across several HRQoL and symptom domains. At the time of considering TKI discontinuation, physicians could inform younger patients that they may expect valuable HRQoL benefits. Considering the marginal improvements observed in patients aged 60 years or above, it may be important to further investigate the value of TFR compared to a lowest effective dose approach in this older group of patients.

Background Basophilia is common in chronic myeloid leukaemia (CML) and is associated with a poor prognosis. Previously it was quantified by percentage and a binary < or ≥ 20%. However, blood basophil concentration at diagnosis may be a better prognostic co-variate. Methods The hypothesis generating cohort was a 135 newly-diagnosed subjects with BCR::ABL1-positive CML receiving a tyrosine kinase-inhibitor (TKI). Median follow-up was 6.3 years (range, 4-16 years). Data were analyzed by Kaplan-Meier curves and multi-variable patient similarity network (PSN). A cohort of 1919 subjects was used to validate the test hypothesis. Subject gave informed consent for non-interventional data collection and the study was approved by Ethics Committees. Results Multi-variable PSNs of the hypothesis generating cohort indicated 5 subject clusters. Incidence of TKI switch was highest in clusters 1 (45%), 5 (40%) and 4 (30%) which were characterized by the increased basophil concentrations at diagnosis compared with clusters 2 (13%) and 3 (14%) with the low basophil concentrations at diagnosis. PSNs identified the combination of basophil concentration ≥ 8x10E+9/L, basophil percentage ≥ 5 % and WBC ≥ 164x10E+9/L to be associated with significantly worse FFS (p < 0.001) and PFS ( p = 0.02) but not survival ( p = 0.18). Basophil concentration ≥ 8x10E+9/L and WBC concentration ≥ 164x10E+9/L were associated with worse EFS (p < 0.001), (FFS (p < 0.001; Figure 1) but not PFS or survival. Basophil percentage at diagnosis had no impact on outcomes using ≥ 5% or ≥ 20% cutoffs. In the validation cohort the combination of basophil concentration ≥ 8x10E+9/L, basophil percentage ≥ 5% and WBC ≥ 164x10E+9/L at diagnosis was associated with worse FFS ( p < 0.001) but not PFS or survival. Basophils ≥ 5% was associated with worse survival ( p = 0.04) and ≥ 20% with worse FFS ( p = 0.04) and survival ( p = 0.009). Basophil concentration ≥ 8×10E+9/L was associated with worse PFS ( p < 0.001; Figure 1) and survival ( p = 0.03). There was no effect of WBC concentration on any outcome. Conclusion We show blood basophil concentration at diagnosis correlates with diverse outcomes in newly-diagnosed persons with CML receiving TKI-therapy. Support IGA_LF_2023_05, MH_CZ-DRO (FNOL, 00098892)

BACKGROUNDInfectious complications during induction chemotherapy of acute myeloid leukaemia are very common. Prophylactic use of antibiotics however is an ongoing challenge in this situation due to bacterial multi-drug resistance. The aim of this study was to provide a comprehensive overview of the incidence of infectious complications in patients with AML undergoing induction therapy using the "7+3" protocol without routine antibiotic prophylaxis at one clinical site providing specialised haematological care in the Czech Republic, over a period of 15 years. The study also evaluates the aetiological spectrum of causative agents and the development of antibiotic resistance in the context of the use of the various classes of antibiotics. The analysis includes evaluation of the importance of risk factors for infectious complications and their impact on treatment of the underlying disease. The data are compared with published figures for similar cohorts of patients.PATIENTS AND METHODSThis study presents a retrospective analysis of infectious complications in 242 patients with acute myeloid leukaemia undergoing the first cycle of induction therapy without routine antibiotic prophylaxis in one clinical site in Czech Republic during years 2006-2020.RESULTSA total of 363 febrile episodes (FE) were recorded. At least 1 FE during the induction was detected in 229 (94.6%) patients. Clinically defined infection was the cause in 96 (26.4%) FEs and blood stream infection in 69 (19.0%) FEs. Both complications occurred simultaneously in 29 (8.0%) FEs. 169 (46.6%) FEs were evaluated as fever of unknown origin (FUO). The achievement of complete remission had a significant effect on the duration of the FE (6 vs. 9 days, P=0.0005) and on the overall survival duration (79.3 vs. 6.5 months, P<0.0001). Patients diagnosed with infection or FUO at diagnosis were significantly more likely to suffer from colonisation by multi-drug resistant bacterial strains at discharge (29.2% vs. 16.3%, P=0.022). This group of patients used antibiotic therapy for a significantly longer time (35 vs. 23 days, P<0.0001). Infection was a contributing cause of death in 18 (7.4%) patients. Mortality was significantly related to the failure to achieve complete remission (P<0.0001).CONCLUSIONInfectious mortality during induction treatment without routine antibiotic prophylaxis was comparable to the published cohorts with prophylaxis. Regular microbiology surveillance with adequate initial antibiotic treatment can compensate routine antibiotic prophylaxis with slower development of antibiotic resistance.

Background For decades, CML has been considered to be a triphasic disease recognizing 3 distinct stages: chronic phase (CP), accelerated phase (AP), and blast crisis (BC). Since the discovery of TKIs, the prognosis of CML patients has rapidly improved and less than 10% of patients diagnosed in CP experience disease progression on the therapy. Based on low incidence of CML progression and the fact that CML biological behavior seems biphasic, the new WHO 2022 classification of CML deemed AP less relevant and suggested the omission of AP. Many experts, however, still advocate for its inclusion in CML classification (e.g. ELN 2020, ICC 2022, NCCN 2023), even though the universal definition of AP is not established and differs in between publications. Methods This retrospective, real-world study is based on the Czech nationwide CML registry INFINITY with the data of newly diagnosed CML patients who agreed and provided their written consent. Recruited subjects were adult patients diagnosed in years 2005 - 2022 with sufficient data to determine the phase of the disease at diagnosis and follow-ups to assess their overall survival (OS), disease specific survival (DSS) and progression-free survival (PFS). The phase of the disease at the time of diagnosis was determined using the classification according to ELN 2020, ICC 2022, WHO 2016, and WHO 2022. Whenever CP was established, EUTOS Long-Term Survival (ELTS) score was calculated, assigning the patient to low risk (LR), intermediate risk (IR) and high risk (HR) group. OS and PFS are defined according to published guidelines. DSS is defined as the time from diagnosis to death due to CML disease or CML treatment. Results During the studied time period, 1660 new cases of CML were reported in INIFINITY registry. Of them, 1500 patients had data sufficient to classify the phase of the disease at the time of the diagnosis according to ELN 2020 guidelines and WHO 2022 classification and 1395 patients had data to assess the phase according to WHO 2016 and ICC 2022 classifications. When using ELN 2020 guidelines, groups were assigned as follows: LR CP- 784 patients (52.3%), IR CP- 421 patients (28.1%), HR CP- 227 patients (15.1%), AP- 42 patients (2.8%), BC- 26 patients (1.7%). There were significant differences in representation by gender, age, comorbidities and performance score amongst patient groups. When comparing just HR CP and AP CML patients, there were no significant differences. Calculated estimates of 5- and 10- year OS, respectively, were 92.5% and 87.2% for LR CP, 83.5% and 65.9% for IR CP, 76.9% and 65.5% for HR CP, 59.2% and 45.9% for AP, and 32.9% for BC, p= 0.031 for HR CP versus AP (Figure 1). In the case of WHO 2016 and ICC 2022 classifications, 714 (51.2%) patients were diagnosed in LR CP, 374 (26.8%) in IR CP, 154 (11.0%) in HR CP, 125 (9.0%) in AP, and 28 (2.0%) in BC. Again, there were significant differences in representation by gender, age, comorbidities and performance score amongst patient groups. When comparing just HR CP and AP CML patients, only age at the time of diagnosis was significantly different. Calculated estimates of 5- and 10- year OS, respectively, were 93.2% and 87.5% for LR CP, 84.9% and 67.7% for IR CP, 80.0% and 69.5% for HR CP, 65.7% and 55.6% for AP, and 39.7% for BC. We also performed propensity score matching according to age for patients in HR CP and AP and calculated estimates of 5- and 10- year OS, respectively, were 85.4% and 74.4% for HR CP and 60.2%, and 52.0% for AP, p= 0.003 (Figure 2). Similar results were obtained when testing for PFS and DSS. Summary Real-world data obtained from 1500 patients diagnosed in Czechia over 17 years, in our opinion, support the need to recognize the existence of AP at the time of diagnosis, even though a singular definition of AP is not agreed upon. Patients in AP have worse survival scores (OS, DSS, PFS) compared to patients in CP and/or HR CP. Moreover, because ELTS risk score was calculated on patients in CP, it may not be suitable for patients in AP, which would be changed to CP according to the new WHO 2022 classification. In conclusion, based on the real-world data with long-term follow-up, we believe it would be reasonable to keep the AP as part of CML classification of newly diagnosed patients. This publication was supported by the grant number MUNI/A/1224/2022, Programme EXCELES, ID Project No. LX22NPO5102, and by the Ministry of Health of the Czech Republic grant number 00023736.

Background: Lower gastrointestinal (GI) graft versus host disease (GVHD) represents a severe complication in allogeneic hematopoietic stem cell transplant (HSCT) recipients with high rates of transplant-related mortality. Deregulated innate immunity reactions are the features of its pathogenesis. Cellular senescence has been considered a program of the innate immunity. We focused on lower GI GVHD from the perspective of cellular senescence. Objective: We analyzed the impact of p16INK4a expression, a hallmark of cellular senescence, in intestinal biopsies of patients with lower GI GVHD symptoms and NFKB1 gene polymorphisms (rs3774937 C/T and rs3774959 A/ G) on HSCT outcome.Study design: Fifty-two single-center patients who presented with symptoms of lower GI GVHD were analyzed in a retrospective manner. Two SNPs located in the NFKB1 gene regions (rs3774937 C/T and rs3774959 A/G) were genotyped from the peripheral blood samples collected before the start of the conditioning. All patients underwent proctosigmoidoscopy with biopsy of the mucosa. The expression of p16INK4a was analyzed in normal intestinal crypts and stroma.Results: Fifty-two patients (50% male) received HSCT for hematological diseases (acute leukemias in 67%) and developed lower GI symptoms. Patients with p16INK4a expression in the intestinal stroma were in lower risk of developing histological grade 3-4 aGVHD (RR 0.18 [95% CI 0.05-0.65]; p = 0.009). The multivariate linear regression confirmed the independent effect of p16INK4a expression on time of the lower GI aGVHD symptoms onset (Coef. 38.9 [95% CI 12.7-65.1]; p = 0.005). The NFKB1 rs3774937 CC and TT/TC genotype were present in 40 and 80% of patients with p16INK4a expression, respectively (p = 0.04). The rs3774959 AA and GG/AG genotype were present among 43 and 82% of patients with p16INK4a expression, respectively (p = 0.02). Expression of p16INK4a was associated with no clinical variable but NFKB1 genotype.Conclusions: Our results address possible new mechanisms that may lead to better understanding of HSCT-related immune complications. Cellular senescence may bring novel approaches in GVHD diagnostics and therapy.

Congenital erythrocytoses represent a heterogenous group of rare defects of erythropoiesis characterized by elevated erythrocyte mass. We performed molecular-genetic analysis of 21 Czech patients with congenital erythrocytosis and assessed the mutual link between chronic erythrocyte overproduction and iron homoeostasis. Causative mutations in erythropoietin receptor (EPOR), hypoxia-inducible factor 2 alpha (HIF2A) or Von Hippel-Lindau (VHL) genes were detected in nine patients, including a novel p.A421Cfs*4 EPOR and a homozygous intronic c.340+770T>C VHL mutation. The association and possible cooperation of five identified missense germline EPOR or Janus kinase 2 (JAK2) variants with other genetic/non-genetic factors in erythrocytosis manifestation may involve variants of Piezo-type mechanosensitive ion channel component 1 (PIEZO1) or Ten-eleven translocation 2 (TET2), but this requires further research. In two families, hepcidin levels appeared to prevent or promote phenotypic expression of the disease. No major contribution of heterozygous haemochromatosis gene (HFE) mutations to the erythrocytic phenotype or hepcidin levels was observed in our cohort. VHL- and HIF2A-mutant erythrocytosis showed increased erythroferrone and suppressed hepcidin, whereas no overproduction of erythroferrone was detected in other patients regardless of molecular defect, age or therapy. Understanding the interplay between iron metabolism and erythropoiesis in different subgroups of congenital erythrocytosis may improve current treatment options.

Background: Stopping TKI treatment in patients with CML is getting more frequent but many questions remain unanswered. It is not even known the proportion of patients who do not actually want to stop the TKI treatment although they are in the long-term deep molecular response. Aims: To determine how many patients with CML in deep molecular response do not wish to stop TKI treatment. To explore any differences between the cohort of patients that agree and disagree with TKI stopping. To evaluate the reasons for the decision not to stop TKI treatment. Methods: In Czechia, by law, the care for adult CML patients is centralized into eight centres. All the centres collaborate within the Czech Leukemia Study Group for Life (CELL) and contribute to the detailed database of CML patients. The Czech nation-wide clinical trial HALF (ClinicalTrials.gov Identifier: NCT04147533), which started in June 2020, tests to stop TKIs in CML patients after the two-step dose reduction. The TKI stopping in the clinical trial HALF is being offered to all suitable CML patients in Czechia. An integral part of the clinical trial was the questionnaire Anti-HALF. All patients who did not want to enter the HALF project were asked to complete this questionnaire. Anti-HALF consists of 20 questions regarding sex, age, occupation, socioeconomic status, TKI therapy and its side effect, compliance, and finally, the reasons for decision not to stop the TKI. The project Anti-HALF was finished at the end of 2022, the HALF project continues. Results: In June 2020, the number of living patients with CML registered in CELL database was 1751. By the end of 2022, the stopping of TKI treatment was offered to 246 of them (14%/1751 pts); 190 of 246 pts (77.2%) were enrolled (HALF patients, H pts), 45 (18.3%) did not want to participate, but completed the Anti-HALF questionnaire (Anti-HALF patients, AH pts), and 11 (4.5%) refused even to complete the survey. There were 143 H pts vs. 36 AH pts on imatinib, 31 H pts vs. 9 AH pts on nilotinib, and 16 H pts vs. 0 AH pts on dasatinib. AH pts were more frequently of female sex (64.4% vs. 46.8%; p=0.046), elderly (median 67.5y vs. 61.8y; p =0.0342), more frequently retired or unemployed (75.6% vs. 54.5%; p=0.0171) and with already reduced dosing of imatinib (55.6% vs. 34.3%; p=0.0223). The factors which did not seem to play a role were the type of TKI and, unexpectedly, the presence of subjective side effects, or the average distance to travel to treating physician. The AH pts took longer their current TKI, but this difference had a borderline statistical significance (median 9.2y vs. 8.0y; p=0.0764). The AH pts were minimally or not stressed during the regular follow up (82.2%), they felt the TKI as effective and safe treatment (57.8%), were very compliant (80.0%), mostly without any subjective side effects of TKI (62.2%). The decision to enter or not the trial was rather difficult for AH pts (53.3%), with serious concern about the disease recurrence (62.2%) and less effective re-treatment (55.6%). Summary/Conclusion: Surprisingly, there is a high proportion of patients with CML who do not wish to stop TKI treatment despite fulfilling the generally accepted stopping criteria. We believe that this is clinically important and so far underexplored phenomenon deserving further study, and this fact has to be taken into the account when counselling the patients. Detailed data will be presented. Supported by the national budget through MEYS, RI CZECRIN (LM2018128) and from ERDF Project CZECRIN_4 PATIENTS (CZ.02.1.01/0.0/0.0/16_013/0001826) and by Ministry of Health of the Czech Republic, grant no. NU22-03-00136 and by National Institute for Cancer Research Project (Programme EXCELES, ID Project No. LX22NPO5102) - Funded by the EuropeanUnion - Next Generation EU. Keywords: Tyrosine kinase inhibitor, treatment-free remission, Chronic myeloid leukemia

The treatment outcome in patients with chronic myeloid leukaemia (CML) in blast crisis (BC) is unsatisfactory despite the use of allogeneic stem cell transplantation (ASCT). Moreover, in some patients ASCT is contraindicated, with limited treatment options. We report the case series of two patients with lymphoid BC CML in whom ASCT was not approachable. The first patient developed BC two months after diagnosis in association with dic(7;9)(p11.2;p11.2) and T315I mutation. Blast crisis with central nervous system leukemic involvement and K611N mutation of the SETD2 gene developed abruptly in the second patient five years after ceasing treatment with nilotinib in major molecular response (MMR) at the patient’s request. Both underwent one course of chemotherapy in combination with rituximab and imatinib, followed by dasatinib and interferon α (INFα) treatment in the first and dasatinib alone in the second case. Deep molecular response (DMR; MR 4.0) was achieved within a short time in both cases. It is probable that DMR was caused by a specific immune response to CML cells, described in both agents. The challenging medical condition that prompted these case series, and the subsequent results, suggest a re-visit to the use of a combination of well-known drugs as an area for further investigation.