Iron overload in lower international prognostic scoring system risk patients with myelodysplastic syndrome receiving red blood cell transfusions: Relation to infections and possible benefit of iron chelation therapy

[Transfusions and iron chelation in myelodysplastic syndromes]

Iron overload (IO) is probably as toxic in elderly patients with low-risk myelodysplastic syndromes (MDS) as in young thalassemic patients. This impact is more difficult to demonstrate because of associated comorbidities. Cardiovascular disease increases vulnerability to the toxic effects of IO. In recent years, registry studies have shown a survival benefit of Iron Chelation Therapy (ICT) in these patients. These findings are now corroborated by an improvement in event-free survival in a single randomized study: the Telesto study. The EFS curves separate after two years of follow-up. This indicates inertia in the occurrence of complications. The benefits of ICT are also very slowly being revealed. It is possible to offer ICT to patients with transfusion-dependent MDS with a life expectancy of at least two years. In Telesto, patients had a serum ferritin (F) level of at least 1000ng/mL, recommendations using this F threshold as a trigger for chelation seem to be reinforced. It remains an open question whether chelation should be started earlier for effective suppression of IO-related oxidative stress. ICTs could be used in transfusion-dependent MDS patients with life expectancy greater than two years. including possibly higher risk patients responding to hypomethylating agents.

High transferrin saturation predicts inferior clinical outcomes in patients with myelodysplastic syndromes

Iron overload (IO) reflected by elevated ferritin is associated with increased mortality in myelodysplastic syndromes (MDS), however, ferritin is an imperfect metric. Elevated labile plasma iron correlates with clinical outcomes and transferrin saturation (TSAT) >80%, but is not readily measurable. The trajectory of TSAT, and its association with clinical outcomes remain undefined. Canadian MDS registry patients were evaluated. Mean TSAT, mean ferritin and transfusion dose density (TDD) were determined. Survival was evaluated by TSAT and ferritin (<50%, 50-80%, >80%), (≤500 μg/L, 501-800 μg/L, >800 μg/L). In 718 patients, median age was 74 years; 12%, 31%, 29%, 15% and 13% were IPSS-R very low, low, intermediate, high and very high. TSAT and ferritin were moderately correlated (r=0.63, P<0.0001). TSAT increased over time in transfusion- dependent patients (P=0.006). Higher TSAT and ferritin were associated with inferior 5-year overall (OS), progression- free (PFS), and leukemia-free survival (LFS) (P≤0.008) and higher TDD with inferior 5-year OS. TSAT >80% trended with inferior cardiac death-free survival (P=0.053). In univariate analysis, age, IPSS-R, blast percentage by Eastern Cooperative Oncology Group Performance Status, frailty, Charlson Comorbidity Index, iron chelation (Y/N), TDD, TSAT and ferritin were significantly associated with inferior OS. By multivariable analysis, TSAT >80% (P=0.007) remained significant for OS (R2 30.3%). In MDS, TSAT >80% and ferritin >800 μg/L portended inferior OS, PFS and LFS. TSAT may indicate the presence of oxidative stress, and is readily measurable in a clinical setting. The relationship between TSAT and cardiac death-free survival warrants further study.

Exploring the rationale for red cell transfusion in myelodysplastic syndrome patients: emerging data and future insights

INTRODUCTION

Anemia is often present in mostly elderly patients with myelodysplastic syndromes (MDS), and is associated with a poorer outcome. Although Red blood cell (RBC) transfusions are the most immediate treatment, waiting for the response to disease-specific therapy, or in case of non-response, the choice of the optimal transfusion regimen is still controversial.

AREAS COVERED

The main objectives of RBC transfusion are the control of anemia-related symptoms and complications and the improvement of functional status and of health-related quality of life (HRQoL). However, RBC transfusions are associated with several negative clinical consequences, mainly adverse transfusion reactions and iron overload, which can be counteracted by iron chelation therapy. Recent few pilot prospective trials have shown a benefit, in terms of HRQoL, of more liberal transfusion regimens, with higher haemoglobin (Hb) targets, compared to conventional restrictive regimens, but these results need confirmation by larger studies.

EXPERT OPINION

: A patient-oriented RBC transfusion therapy in MDS patients must take into account several laboratory (Hb), clinical (age, comorbidities), psychological, family and social factors, and evaluation of HRQoL should become a fundamental parameter in assessing the clinical benefit of therapy. Many questions remain to be clarified, including why some patients report little benefit from transfusions.

Prognostic Factors and Clinical Considerations for Iron Chelation Therapy in Myelodysplastic Syndrome Patients

Iron chelation therapy (ICT) is an important tool in the treatment of transfusion-dependent lower-risk myelodysplastic syndrome (MDS) patients. ICT is effective in decreasing iron overload and consequently in limiting its detrimental effects on several organs, such as the heart, liver, and endocrine glands. Besides this effect, ICT also proved to be effective in improving peripheral cytopenia in a significant number of MDS patients, thus further increasing the clinical interest of this therapeutic tool. In the first part of the review, we will analyze the toxic effect of iron overload and its mechanism. Subsequently, we will revise the clinical role of ICT in various subsets of MDS patients (low, intermediate, and high risk MDS, patients who are candidates for allogeneic stem cell transplantation).

Iron overload-induced oxidative stress in myelodysplastic syndromes and its cellular sequelae

The myelodysplastic syndromes (MDS) are clonal hematopoietic stem cell disorders. MDS patients often require red blood cell transfusions, resulting in iron overload (IOL). IOL increases production of reactive oxygen species (ROS), oxygen free radicals. We review and illustrate how IOL-induced ROS influence cellular activities relevant to MDS pathophysiology. ROS damage lipids, nucleic acids in mitochondrial and nuclear DNA, structural proteins, transcription factors and enzymes. Cellular consequences include decreased metabolism and tissue and organ dysfunction. In hematopoietic stem cells (HSC), consequences of ROS include decreased glycolysis, shifting the cell from anaerobic to aerobic metabolism and causing HSC to exit the quiescent state, leading to HSC exhaustion or senescence. ROS oxidizes DNA bases, resulting in accumulation of mutations. Membrane oxidation alters fluidity and permeability. In summary, evidence indicates that IOL-induced ROS alters cellular signaling pathways resulting in toxicity to organs and hematopoietic cells, in keeping with adverse clinical outcomes in MDS.

Modulation of the Immune Response by Deferasirox in Myelodysplastic Syndrome Patients

Deferasirox (DFX) is an oral iron chelator used to reduce iron overload (IO) caused by frequent blood cell transfusions in anemic myelodysplastic syndrome (MDS) patients. To study the molecular mechanisms by which DFX improves outcome in MDS, we analyzed the global gene expression in untreated MDS patients and those who were given DFX treatment. The gene expression profiles of bone marrow CD34⁺ cells were assessed by whole-genome microarrays. Initially, differentially expressed genes (DEGs) were determined between patients with normal ferritin levels and those with IO to address the effect of excessive iron on cellular pathways. These DEGs were annotated to Gene Ontology terms associated with cell cycle, apoptosis, adaptive immune response and protein folding and were enriched in cancer-related pathways. The deregulation of multiple cancer pathways in iron-overloaded patients suggests that IO is a cofactor favoring the progression of MDS. The DEGs between patients with IO and those treated with DFX were involved predominantly in biological processes related to the immune response and inflammation. These data indicate DFX modulates the immune response mainly via neutrophil-related genes. Suppression of negative regulators of blood cell differentiation essential for cell maturation and upregulation of heme metabolism observed in DFX-treated patients may contribute to the hematopoietic improvement.

Controversies on the Consequences of Iron Overload and Chelation in MDS

Many patients with MDS are prone to develop systemic and tissue iron overload in part as a consequence of disease-immanent ineffective erythropoiesis. However, chronic red blood cell transfusions, which are part of the supportive care regimen to correct anemia, are the major source of iron overload in MDS. Increased systemic iron levels eventually lead to the saturation of the physiological systemic iron carrier transferrin and the occurrence of non-transferrin-bound iron (NTBI) together with its reactive fraction, the labile plasma iron (LPI). NTBI/LPI-mediated toxicity and tissue iron overload may exert multiple detrimental effects that contribute to the pathogenesis, complications and eventually evolution of MDS. Until recently, the evidence supporting the use of iron chelation in MDS was based on anecdotal reports, uncontrolled clinical trials or prospective registries. Despite not fully conclusive, these and more recent studies, including the TELESTO trial, unravel an overall adverse action of iron overload and therapeutic benefit of chelation, ranging from improved hematological outcome, reduced transfusion dependence and superior survival of iron-loaded MDS patients. The still limited and somehow controversial experimental and clinical data available from preclinical studies and randomized trials highlight the need for further investigation to fully elucidate the mechanisms underlying the pathological impact of iron overload-mediated toxicity as well as the effect of classic and novel iron restriction approaches in MDS. This review aims at providing an overview of the current clinical and translational debated landscape about the consequences of iron overload and chelation in the setting of MDS.

Efficacy and safety of iron chelator for transfusion-dependent patients with myelodysplastic syndrome: a meta-analysis

To systematically evaluate the efficacy and safety of iron chelators for transfusion-dependent patients with MDS. Thirteen cohort studies with 12,990 patients diagnosed with MDS were included in this study. According to m eta-analysis results transfusion-dependent MDS patients with secondary iron overload had a longer (HR = 0.52, 95%CI = 0.43-0.62, P < 0.001). Further subgroup analysis revealed a longer LFS (HR = 0.84, 95%CI = 0.76-0.93, P = 0.001) in MDS patients receiving iron chelators than in MDS patients not receiving iron chelators (HR = 0.52, 95%CI = 0.43-0.62, P < 0.001) and in patients with lower-risk MDS (HR = 0.50, 95%CI = 0.43-0.59, P < 0.001). Subgroup analysis of DFX showed that compared with patients not treated with iron chelators, the group receiving DFX monotherapy had significantly increased OS (HR = 0.43, 95%CI = 0.27-0.69, P < 0.001). In terms of tolerance, meta-analysis of binary variables in CAEs indicated that the occurrence of CAEs was significantly reduced by ICT (RR = 0.64, 95%CI = 0.57-0.71, P < 0.001).

Increased incidence of infection in patients with myelofibrosis and transfusion-associated iron overload in the clinical setting

Transfusion-associated iron overload may lead to increased risk of infection, but its role in myelofibrosis (MF) has been scarcely explored. We evaluated 106 consecutive patients with primary or secondary MF. Up to 38% of patients were transfusion-dependent (TD) with a median of 14 RBC units received. Median observation time was 36 months (range 3-203). Forty-five percent of patients experienced one or more infectious episodes for a total of 69 infectious events, 13 (19%) of which were severe. The 60-month cumulative incidence of infection was 64.1 ± 6.5%. TD patients showed a higher incidence of infection (HR = 2.13, p = 0.019). Transfusion burden was markedly greater in TD patients with infectious complication (median 24 RBC units vs 15 RBC units; p = 0.012). The 60-month overall survival was 40 ± 5.9%. Lower International Prognostic Scoring System (IPSS) risk (p < 0.0001) and ruxolitinib (p = 0.027) were significantly correlated with higher survival. This real-world study showed increased infections in patients with higher transfusion burden. It may therefore be interesting to further investigate the role of iron chelation in improving infection-free survival in MF patients.

Iron Overload Mimicking Conditions Skews Bone Marrow Dendritic Cells Differentiation into MHCIIlowCD11c+CD11b+F4/80+ Cells

Iron overload is an undesired effect of frequent blood transfusions or genetic diseases. Myelodysplastic syndrome (MDS) patients become transfusion dependent, but due to the combination of ineffective haematopoiesis and repeated blood transfusions they are often subject to iron overload. In this study, we demonstrate that iron-overload mimicking condition alters bone marrow progenitor differentiation towards dendritic cells (DCs). Cells cultured in iron-enriched culture medium for seven days fail to differentiate into conventional CD11c⁺MHCII^hi DCs and fail to efficiently respond to LPS (Lipopolysaccharides). Cells appear smaller than control DCs but vital and able to perform FITC-dextran (Fluorescein isothiocyanate-dextran) endocytosis. At molecular level, cells cultured in iron-enriched conditions show increased ARG1 and PU.1, and decreased IRF8 expression.

Delayed time from RBC transfusion dependence to first cardiac event in lower IPSS risk MDS patients receiving iron chelation therapy

Transfused MDS patients are at risk for iron overload (IOL). IOL may exacerbate congestive heart failure (CHF), coronary artery disease (CAD) and arrythmias (ARR). We retrospectively examined cardiac events (CE) in red blood cell (RBC) transfusion dependent (TD) lower IPSS risk MDS patients. Patients were censored at death or MDS progression. 151 MDS patients were lower IPSS risk and RBC TD. Median number of cardiac risk factors (RF) per patient was 1 (1-4). CE following RBC TD occurred in 48 (32%) and were: CHF, n = 20; CAD, n = 15; ARR, n = 11. In univariate analysis factors significant for time to (TT) CE were: age at 1st RBC transfusion; number of RBCU transfused while lower IPSS risk; received iron chelation therapy (ICT); MDS treatment received; and number of cardiac RF/patient (p ≤ 0.02). Receiving ICT remained significant for TTCE in multivariate analysis (p = 0.03). Median TTCE in patients not receiving and receiving ICT was 7.0 (0.1-65.0) and 20.0 (0.1-148.6) months, respectively (p = 0.02). For lower IPSS risk RBC transfusion dependent MDS patients, time to first cardiac event following RBC TD was significantly longer in patients receiving ICT. These results suggest ICT may delay cardiac events in transfused patients. The results should be confirmed in larger numbers in prospective analyses.

Iron overload in myelodysplastic syndromes: Evidence based guidelines from the Canadian consortium on MDS

In 2008 the first evidence-based Canadian consensus guideline addressing the diagnosis, monitoring and management of transfusional iron overload in patients with myelodysplastic syndromes (MDS) was published. The Canadian Consortium on MDS, comprised of hematologists from across Canada with a clinical and academic interest in MDS, reconvened to update these guidelines. A literature search was updated in 2017; topics reviewed include mechanisms of iron overload induced cellular damage, evidence for clinical endpoints impacted by iron overload including organ dysfunction, infections, marrow failure, overall survival, acute myeloid leukemia progression, and endpoints around hematopoietic stem-cell transplant. Evidence for an impact of iron reduction on the same endpoints is discussed, guidelines are updated, and areas identified where evidence is suboptimal. The guidelines address common questions around the diagnosis, workup and management of iron overload in clinical practice, and take the approach of who, when, why and how to treat iron overload in MDS. Practical recommendations for treatment and monitoring are made. Evidence levels and grading of recommendations are provided for all clinical endpoints examined.

Infections in Myelodysplastic Syndrome in Relation to Stage and Therapy

Infections remain a significant problem in myelodysplastic syndromes (MDS) in treated as well in non-treated patients and assume a particular complexity. The susceptibility to infections is due, in the absence of intensive chemotherapies, mainly to functional defects in the myeloid lineage with or without neutropenia. Furthermore, MDS includes a heterogeneous group of patients with very different prognosis, therapy and risk factors regarding survival and infections. You should distinguish risk factors related to the disease, like as neutrophils function impairment, neutropenia, unfavorable cytogenetics and bone marrow insufficiency; factors related to the patient, like as age and comorbidities, and factors related to the therapy. When the patients with MDS are submitted to intensive chemotherapy with and without hematopoietic stem cell transplantation (HSCT), they have a risk factor for infection very similar to that of patients with acute myeloid leukemia (AML), and mostly related to neutropenia. Patients with MDS treated with supportive therapy only or with demethylating agent or lenalidomide or immunosuppressive drugs should have a tailored approach. Most of the infections in MDS originate from bacteria, and the main risk factors are represented by neutropenia, thrombocytopenia, and unfavorable cytogenetics. Thus, it is reasonable to give antibacterial prophylaxis to patients who start the therapy with demethylating agents with a number of neutrophils <500 × 10⁹/L, or with thrombocytopenia and unfavorable cytogenetics. The antifungal prophylaxis is not considered cost/benefit adequate and should be taken into consideration only when there is an antecedent fungal infection or presence of filamentous fungi in the surveillance cultures. Subjects submitted to immunosuppression with ATG+CSA have a high rate of infections, and when severely neutropenic should ideally be nursed in isolation, should be given prophylactic antibiotics and antifungals, regular mouth care including an antiseptic mouthwash.

Iron overload impairs normal hematopoietic stem and progenitor cells through reactive oxygen species and shortens survival in myelodysplastic syndrome mice

There is increasing clinical evidence to suggest a suppressive effect on hematopoiesis in myelodysplastic syndrome patients with iron overload. However, how iron overload influences hematopoiesis in myelodysplastic syndrome (MDS) remains unknown. Here, the RUNX1S291fs-transduced bone marrow mononuclear cells were yielded and transplanted into lethally irradiated recipient mice together with radioprotective bone marrow cells to generate MDS mice. Eight weeks post transplantation, the recipient mice received an intraperitoneal injection of 0.2 mL iron dextran at a concentration of 25 mg/mL once every other day for a total of 8 times to establish an iron overload model. In the present study, we show that iron overload impairs the frequency and colony-forming capacity of normal hematopoietic stem and progenitor cells, especially in erythroid, in MDS mice, which is due, at least in part, to growth differentiation factor 11-induced reactive oxygen species, shortening survival of MDS mice. Given that we are the first to construct an iron overload model in MDS mice, we hope this model will be helpful for further exploring the influence and mechanism of iron overload on MDS.