Prevention of secondary stroke and resolution of transfusional iron overload in children with sickle cell anemia using hydroxyurea and phlebotomy

Hydroxyurea for secondary stroke prevention in children with sickle cell anaemia: a systematic review of clinical evidence and outcomes

Background

Stroke remains one of the leading complications of sickle cell anaemia (SCA) in children. Traditionally, SCA treatment focused on symptom relief. However, the high incidence of strokes in children has prompted a reevaluation of treatment, particularly hydroxyurea, for secondary stroke prevention. This study assesses hydroxyurea's effectiveness and safety in preventing secondary strokes in paediatric SCA patients.

Methods

This systematic review followed a pre-defined protocol registered with PROSPERO. Comprehensive searches were conducted across PubMed, Embase, Scopus, MEDLINE, Google Scholar, and the Cochrane Library up to August 2023. Studies were included involving paediatric SCA patients at risk of secondary stroke, assessing hydroxyurea as the primary intervention.

Results

A total of six studies meeting inclusion criteria were included. The effectiveness of hydroxyurea in preventing secondary strokes, with variable responses reported across studies. Adverse effects, including mild neutropenia, are associated with hydroxyurea treatment but with variability in reported toxicity levels.

Conclusion

Hydroxyurea holds promise in preventing recurrent strokes in children with SCA, though its efficacy and safety profiles vary among individuals. Optimal dosages and treatment durations require further investigation, necessitating vigilant monitoring of haematological parameters. Future research should refine dosing strategies, consider individual patient characteristics, assess long-term effects, and explore ancillary benefits beyond stroke prevention.

Improving the Capacity of Health System and Community for Sickle Cell Disease Screening and Management Among Tribal Population in India: Protocol of an Intervention Study

Sickle cell disease (SCD) is one of the major public health problems in the world. In India, the burden of SCD is comparatively high in socio-economically disadvantaged tribal communities. Though efficacious interventions are available to manage SCD, they are not reaching to these communities and no comprehensive programme is in place in the health care system. Therefore, the Indian Council of Medical Research has initiated a nation-wide study to develop an effective intervention model for SCD patients in tribal areas through the government health care system. This intervention includes increasing awareness and preparing the communities for accessing the government health care system for SCD care, and improving the capacity of the primary health care systems including the training of the health care providers on prevention and management of SCD. The study adopted a quasi-experimental design with pre-vs. post-intervention comparisons of outcome variables within the interventional groups and with the control group. The study will be implemented in 6 districts which are endemic for SCD, spread across different geographical zones of India. In each district, four primary health centre (PHC) areas which are predominantly inhabited by tribal population will be selected. Of these four PHC areas, two will be selected randomly for implementing the intervention and the remaining two will be the control area. Information necessary for development and implementation of the intervention will be gathered during formative research, by using both quantitative and qualitative research methods. Intervention with an inclusive partnership and community mobilization will be implemented. The major steps in the implementation of intervention are partnership building with various health and non-health partners including the community. Capacity building and strengthening is another important component to enable the primary health facilities to screen and manage SCD patients. Primarily, sub-health centres and primary healthcare centres will be equipped with appropriate SCD screening techniques. All doctors in the system will be trained in advanced treatment and management issues. To improve the community's awareness and readiness, community mobilization activities will be conducted. An impact evaluation will be carried out at the end of the intervention by comparing the improvement of SCD management in intervention PHCs to that of the control PHCs. However, the process evaluation and necessary mid-term corrections will be made throughout the intervention period. Thus, an intervention model in terms of its suitability, replicability and sustainability for the tribal population will be developed and tested. The findings of this study are more suitable to use during advocacy and to replicate the model by the state health departments. This study develops and places an appropriate referral system for SCD patients at the PHC level. Improving the community's access to health care, improving the quality of care in government health centres and raising awareness among tribal communities are crucial to achieving through innovation. Taken together, these innovations would significantly contribute to better access to health care and management of the SCD patients of underserved tribal population.

Blood transfusion for preventing primary and secondary stroke in people with sickle cell disease

BACKGROUND

Sickle cell disease is one of the commonest severe monogenic disorders in the world, due to the inheritance of two abnormal haemoglobin (beta globin) genes. Sickle cell disease can cause severe pain, significant end-organ damage, pulmonary complications, and premature death. Stroke affects around 10% of children with sickle cell anaemia (HbSS). Chronic blood transfusions may reduce the risk of vaso-occlusion and stroke by diluting the proportion of sickled cells in the circulation. This is an update of a Cochrane Review first published in 2002, and last updated in 2017.

OBJECTIVES

To assess risks and benefits of chronic blood transfusion regimens in people with sickle cell disease for primary and secondary stroke prevention (excluding silent cerebral infarcts).

SEARCH METHODS

We searched for relevant trials in the Cochrane Library, MEDLINE (from 1946), Embase (from 1974), the Transfusion Evidence Library (from 1980), and ongoing trial databases; all searches current to 8 October 2019. We searched the Cochrane Cystic Fibrosis and Genetic Disorders Group Haemoglobinopathies Trials Register: 19 September 2019.

SELECTION CRITERIA

Randomised controlled trials comparing red blood cell transfusions as prophylaxis for stroke in people with sickle cell disease to alternative or standard treatment. There were no restrictions by outcomes examined, language or publication status.

DATA COLLECTION AND ANALYSIS

Two authors independently assessed trial eligibility and the risk of bias and extracted data.

MAIN RESULTS

We included five trials (660 participants) published between 1998 and 2016. Four of these trials were terminated early. The vast majority of participants had the haemoglobin (Hb)SS form of sickle cell disease. Three trials compared regular red cell transfusions to standard care in primary prevention of stroke: two in children with no previous long-term transfusions; and one in children and adolescents on long-term transfusion. Two trials compared the drug hydroxyurea (hydroxycarbamide) and phlebotomy to long-term transfusions and iron chelation therapy: one in primary prevention (children); and one in secondary prevention (children and adolescents). The quality of the evidence was very low to moderate across different outcomes according to GRADE methodology. This was due to the trials being at a high risk of bias due to lack of blinding, indirectness and imprecise outcome estimates. Red cell transfusions versus standard care Children with no previous long-term transfusions Long-term transfusions probably reduce the incidence of clinical stroke in children with a higher risk of stroke (abnormal transcranial doppler velocities or previous history of silent cerebral infarct), risk ratio 0.12 (95% confidence interval 0.03 to 0.49) (two trials, 326 participants), moderate quality evidence. Long-term transfusions may: reduce the incidence of other sickle cell disease-related complications (acute chest syndrome, risk ratio 0.24 (95% confidence interval 0.12 to 0.48)) (two trials, 326 participants); increase quality of life (difference estimate -0.54, 95% confidence interval -0.92 to -0.17) (one trial, 166 participants); but make little or no difference to IQ scores (least square mean: 1.7, standard error 95% confidence interval -1.1 to 4.4) (one trial, 166 participants), low quality evidence. We are very uncertain whether long-term transfusions: reduce the risk of transient ischaemic attacks, Peto odds ratio 0.13 (95% confidence interval 0.01 to 2.11) (two trials, 323 participants); have any effect on all-cause mortality, no deaths reported (two trials, 326 participants); or increase the risk of alloimmunisation, risk ratio 3.16 (95% confidence interval 0.18 to 57.17) (one trial, 121 participants), very low quality evidence. Children and adolescents with previous long-term transfusions (one trial, 79 participants) We are very uncertain whether continuing long-term transfusions reduces the incidence of: stroke, risk ratio 0.22 (95% confidence interval 0.01 to 4.35); or all-cause mortality, Peto odds ratio 8.00 (95% confidence interval 0.16 to 404.12), very low quality evidence. Several review outcomes were only reported in one trial arm (sickle cell disease-related complications, alloimmunisation, transient ischaemic attacks). The trial did not report neurological impairment, or quality of life. Hydroxyurea and phlebotomy versus red cell transfusions and chelation Neither trial reported on neurological impairment, alloimmunisation, or quality of life. Primary prevention, children (one trial, 121 participants) Switching to hydroxyurea and phlebotomy may have little or no effect on liver iron concentrations, mean difference -1.80 mg Fe/g dry-weight liver (95% confidence interval -5.16 to 1.56), low quality evidence. We are very uncertain whether switching to hydroxyurea and phlebotomy has any effect on: risk of stroke (no strokes); all-cause mortality (no deaths); transient ischaemic attacks, risk ratio 1.02 (95% confidence interval 0.21 to 4.84); or other sickle cell disease-related complications (acute chest syndrome, risk ratio 2.03 (95% confidence interval 0.39 to 10.69)), very low quality evidence. Secondary prevention, children and adolescents (one trial, 133 participants) Switching to hydroxyurea and phlebotomy may: increase the risk of sickle cell disease-related serious adverse events, risk ratio 3.10 (95% confidence interval 1.42 to 6.75); but have little or no effect on median liver iron concentrations (hydroxyurea, 17.3 mg Fe/g dry-weight liver (interquartile range 10.0 to 30.6)); transfusion 17.3 mg Fe/g dry-weight liver (interquartile range 8.8 to 30.7), low quality evidence. We are very uncertain whether switching to hydroxyurea and phlebotomy: increases the risk of stroke, risk ratio 14.78 (95% confidence interval 0.86 to 253.66); or has any effect on all-cause mortality, Peto odds ratio 0.98 (95% confidence interval 0.06 to 15.92); or transient ischaemic attacks, risk ratio 0.66 (95% confidence interval 0.25 to 1.74), very low quality evidence.

AUTHORS' CONCLUSIONS

There is no evidence for managing adults, or children who do not have HbSS sickle cell disease. In children who are at higher risk of stroke and have not had previous long-term transfusions, there is moderate quality evidence that long-term red cell transfusions reduce the risk of stroke, and low quality evidence they also reduce the risk of other sickle cell disease-related complications. In primary and secondary prevention of stroke there is low quality evidence that switching to hydroxyurea with phlebotomy has little or no effect on the liver iron concentration. In secondary prevention of stroke there is low-quality evidence that switching to hydroxyurea with phlebotomy increases the risk of sickle cell disease-related events. All other evidence in this review is of very low quality.

Intermittent or uneven daily administration of low-dose hydroxyurea is effective in treating children with sickle cell anemia in Angola

BACKGROUND

Although hydroxyurea is proven effective in treatment of sickle cell anemia (SCA) and is widely prescribed in high-income countries, due to questions about feasibility of treating large numbers of patients in resource-limited health systems, its use is limited in sub-Saharan Africa (SSA), where most children with SCA live. We assessed hematological response and toxicity of hydroxyurea treatment for SCA in Angola.

METHODS

Retrospective study of children with SCA (not selected for clinical severity) treated on a fixed dose of hydroxyurea for at least 6 months. Because only the 500 mg capsule was available, dose was averaged weekly. We evaluated toxicity events and magnitude of hydroxyurea-induced changes in blood counts and compared patients who received a uniform daily dose to those prescribed intermittent or uneven daily doses.

RESULTS

Only 13% of 303 patients received a uniform dose of hydroxyurea daily. Dose ranged from 16.5 to 22.8 mg/kg/day. Hydroxyurea increased HGB and mean cell volume values by 0.5 g/dL (P < 0.0001) and 8 fL (P < 0.0001), while ANC, PLT, and ARC decreased 1.1 × 10⁹ /L (P < 0.0001), 34 × 10⁹ /L (P = < 0.0001), and 19 × 10⁹ /L (P = 0.0008), respectively. There were no differences in magnitude of hydroxyurea-induced changes between patients prescribed intermittent or uneven doses and uniform daily doses, or between those treated in the lower and higher dose quartiles. Hematological toxicity events were mild and reversible.

CONCLUSION

Intermittent or uneven daily dosing of hydroxyurea is as effective as fixed daily doses in treating SCA. This strategy may enable treatment of additional children with SCA in SSA.

Sickle cell disease

Sickle cell disease is a common and life-threatening haematological disorder that affects millions of people worldwide. Abnormal sickle-shaped erythrocytes disrupt blood flow in small vessels, and this vaso-occlusion leads to distal tissue ischaemia and inflammation, with symptoms defining the acute painful sickle-cell crisis. Repeated sickling and ongoing haemolytic anaemia, even when subclinical, lead to parenchymal injury and chronic organ damage, causing substantial morbidity and early mortality. Currently available treatments are limited to transfusions and hydroxycarbamide, although stem cell transplantation might be a potentially curative therapy. Several new therapeutic options are in development, including gene therapy and gene editing. Recent advances include systematic universal screening for stroke risk, improved management of iron overload using oral chelators and non-invasive MRI measurements, and point-of-care diagnostic devices. Controversies include the role of haemolysis in sickle cell disease pathophysiology, optimal management of pregnancy, and strategies to prevent cerebrovascular disease.

Hydroxycarbamine: from an Old Drug Used in Malignant Hemopathies to a Current Standard in Sickle Cell Disease

While hydroxycarbamide (hydroxyurea, HU) has less and fewer indications in malignant hemopathies, it represents the only widely used drug which modifies sickle cell disease pathogenesis. Clinical experience with HU for patients with sickle cell disease has been accumulated over the past 25 years in Western countries. The review of the literature provides increasing support for safety and efficacy in both children and adults for reducing acute vaso-occlusive events including pain episodes and acute chest syndrome. No increased incidence of leukemia and teratogenicity was demonstrated. HU has become the standard-of-care for sickle cell anemia but remains underused. Barriers to its use should be identified and overcome.

Blood transfusion for preventing primary and secondary stroke in people with sickle cell disease

BACKROUND

Sickle cell disease is one of the commonest severe monogenic disorders in the world, due to the inheritance of two abnormal haemoglobin (beta globin) genes. Sickle cell disease can cause severe pain, significant end-organ damage, pulmonary complications, and premature death. Stroke affects around 10% of children with sickle cell anaemia (HbSS). Chronic blood transfusions may reduce the risk of vaso-occlusion and stroke by diluting the proportion of sickled cells in the circulation.This is an update of a Cochrane Review first published in 2002, and last updated in 2013.

OBJECTIVES

To assess risks and benefits of chronic blood transfusion regimens in people with sickle cell disease for primary and secondary stroke prevention (excluding silent cerebral infarcts).

SEARCH METHODS

We searched for relevant trials in the Cochrane Library, MEDLINE (from 1946), Embase (from 1974), the Transfusion Evidence Library (from 1980), and ongoing trial databases; all searches current to 04 April 2016.We searched the Cochrane Cystic Fibrosis and Genetic Disorders Group Haemoglobinopathies Trials Register: 25 April 2016.

SELECTION CRITERIA

Randomised controlled trials comparing red blood cell transfusions as prophylaxis for stroke in people with sickle cell disease to alternative or standard treatment. There were no restrictions by outcomes examined, language or publication status.

DATA COLLECTION AND ANALYSIS

Two authors independently assessed trial eligibility and the risk of bias and extracted data.

MAIN RESULTS

We included five trials (660 participants) published between 1998 and 2016. Four of these trials were terminated early. The vast majority of participants had the haemoglobin (Hb)SS form of sickle cell disease.Three trials compared regular red cell transfusions to standard care in primary prevention of stroke: two in children with no previous long-term transfusions; and one in children and adolescents on long-term transfusion.Two trials compared the drug hydroxyurea (hydroxycarbamide) and phlebotomy to long-term transfusions and iron chelation therapy: one in primary prevention (children); and one in secondary prevention (children and adolescents).The quality of the evidence was very low to moderate across different outcomes according to GRADE methodology. This was due to the trials being at a high risk of bias due to lack of blinding, indirectness and imprecise outcome estimates. Red cell transfusions versus standard care Children with no previous long-term transfusionsLong-term transfusions probably reduce the incidence of clinical stroke in children with a higher risk of stroke (abnormal transcranial doppler velocities or previous history of silent cerebral infarct), risk ratio 0.12 (95% confidence interval 0.03 to 0.49) (two trials, 326 participants), moderate quality evidence.Long-term transfusions may: reduce the incidence of other sickle cell disease-related complications (acute chest syndrome, risk ratio 0.24 (95% confidence interval 0.12 to 0.48)) (two trials, 326 participants); increase quality of life (difference estimate -0.54, 95% confidence interval -0.92 to -0.17) (one trial, 166 participants); but make little or no difference to IQ scores (least square mean: 1.7, standard error 95% confidence interval -1.1 to 4.4) (one trial, 166 participants), low quality evidence.We are very uncertain whether long-term transfusions: reduce the risk of transient ischaemic attacks, Peto odds ratio 0.13 (95% confidence interval 0.01 to 2.11) (two trials, 323 participants); have any effect on all-cause mortality, no deaths reported (two trials, 326 participants); or increase the risk of alloimmunisation, risk ratio 3.16 (95% confidence interval 0.18 to 57.17) (one trial, 121 participants), very low quality evidence. Children and adolescents with previous long-term transfusions (one trial, 79 participants)We are very uncertain whether continuing long-term transfusions reduces the incidence of: stroke, risk ratio 0.22 (95% confidence interval 0.01 to 4.35); or all-cause mortality, Peto odds ratio 8.00 (95% confidence interval 0.16 to 404.12), very low quality evidence.Several review outcomes were only reported in one trial arm (sickle cell disease-related complications, alloimmunisation, transient ischaemic attacks).The trial did not report neurological impairment, or quality of life. Hydroxyurea and phlebotomy versus red cell transfusions and chelationNeither trial reported on neurological impairment, alloimmunisation, or quality of life. Primary prevention, children (one trial, 121 participants)Switching to hydroxyurea and phlebotomy may have little or no effect on liver iron concentrations, mean difference -1.80 mg Fe/g dry-weight liver (95% confidence interval -5.16 to 1.56), low quality evidence.We are very uncertain whether switching to hydroxyurea and phlebotomy has any effect on: risk of stroke (no strokes); all-cause mortality (no deaths); transient ischaemic attacks, risk ratio 1.02 (95% confidence interval 0.21 to 4.84); or other sickle cell disease-related complications (acute chest syndrome, risk ratio 2.03 (95% confidence interval 0.39 to 10.69)), very low quality evidence. Secondary prevention, children and adolescents (one trial, 133 participants)Switching to hydroxyurea and phlebotomy may: increase the risk of sickle cell disease-related serious adverse events, risk ratio 3.10 (95% confidence interval 1.42 to 6.75); but have little or no effect on median liver iron concentrations (hydroxyurea, 17.3 mg Fe/g dry-weight liver (interquartile range 10.0 to 30.6)); transfusion 17.3 mg Fe/g dry-weight liver (interquartile range 8.8 to 30.7), low quality evidence.We are very uncertain whether switching to hydroxyurea and phlebotomy: increases the risk of stroke, risk ratio 14.78 (95% confidence interval 0.86 to 253.66); or has any effect on all-cause mortality, Peto odds ratio 0.98 (95% confidence interval 0.06 to 15.92); or transient ischaemic attacks, risk ratio 0.66 (95% confidence interval 0.25 to 1.74), very low quality evidence.

AUTHORS' CONCLUSIONS

There is no evidence for managing adults, or children who do not have HbSS sickle cell disease.In children who are at higher risk of stroke and have not had previous long-term transfusions, there is moderate quality evidence that long-term red cell transfusions reduce the risk of stroke, and low quality evidence they also reduce the risk of other sickle cell disease-related complications.In primary and secondary prevention of stroke there is low quality evidence that switching to hydroxyurea with phlebotomy has little or no effect on the liver iron concentration.In secondary prevention of stroke there is low-quality evidence that switching to hydroxyurea with phlebotomy increases the risk of sickle cell disease-related events.All other evidence in this review is of very low quality.

Hydroxycarbamide versus chronic transfusion for maintenance of transcranial doppler flow velocities in children with sickle cell anaemia-TCD With Transfusions Changing to Hydroxyurea (TWiTCH): a multicentre, open-label, phase 3, non-inferiority trial

BACKGROUND

For children with sickle cell anaemia and high transcranial doppler (TCD) flow velocities, regular blood transfusions can effectively prevent primary stroke, but must be continued indefinitely. The efficacy of hydroxycarbamide (hydroxyurea) in this setting is unknown; we performed the TWiTCH trial to compare hydroxyurea with standard transfusions.

METHODS

TWiTCH was a multicentre, phase 3, randomised, open-label, non-inferiority trial done at 26 paediatric hospitals and health centres in the USA and Canada. We enrolled children with sickle cell anaemia who were aged 4-16 years and had abnormal TCD flow velocities (≥ 200 cm/s) but no severe vasculopathy. After screening, eligible participants were randomly assigned 1:1 to continue standard transfusions (standard group) or hydroxycarbamide (alternative group). Randomisation was done at a central site, stratified by site with a block size of four, and an adaptive randomisation scheme was used to balance the covariates of baseline age and TCD velocity. The study was open-label, but TCD examinations were read centrally by observers masked to treatment assignment and previous TCD results. Participants assigned to standard treatment continued to receive monthly transfusions to maintain 30% sickle haemoglobin or lower, while those assigned to the alternative treatment started oral hydroxycarbamide at 20 mg/kg per day, which was escalated to each participant's maximum tolerated dose. The treatment period lasted 24 months from randomisation. The primary study endpoint was the 24 month TCD velocity calculated from a general linear mixed model, with the non-inferiority margin set at 15 cm/s. The primary analysis was done in the intention-to-treat population and safety was assessed in all patients who received at least one dose of assigned treatment. This study is registered with ClinicalTrials.gov, number NCT01425307.

FINDINGS

Between Sept 20, 2011, and April 17, 2013, 159 patients consented and enrolled in TWiTCH. 121 participants passed screening and were then randomly assigned to treatment (61 to transfusions and 60 to hydroxycarbamide). At the first scheduled interim analysis, non-inferiority was shown and the sponsor terminated the study. Final model-based TCD velocities were 143 cm/s (95% CI 140-146) in children who received standard transfusions and 138 cm/s (135-142) in those who received hydroxycarbamide, with a difference of 4·54 (0·10-8·98). Non-inferiority (p=8·82 × 10(-16)) and post-hoc superiority (p=0·023) were met. Of 29 new neurological events adjudicated centrally by masked reviewers, no strokes were identified, but three transient ischaemic attacks occurred in each group. Magnetic resonance brain imaging and angiography (MRI and MRA) at exit showed no new cerebral infarcts in either treatment group, but worsened vasculopathy in one participant who received standard transfusions. 23 severe adverse events in nine (15%) patients were reported for hydroxycarbamide and ten serious adverse events in six (10%) patients were reported for standard transfusions. The most common serious adverse event in both groups was vaso-occlusive pain (11 events in five [8%] patients with hydroxycarbamide and three events in one [2%] patient for transfusions).

INTERPRETATION

For high-risk children with sickle cell anaemia and abnormal TCD velocities who have received at least 1 year of transfusions, and have no MRA-defined severe vasculopathy, hydroxycarbamide treatment can substitute for chronic transfusions to maintain TCD velocities and help to prevent primary stroke.

FUNDING

National Heart, Lung, and Blood Institute, National Institutes of Health.

Optimizing hydroxyurea therapy for sickle cell anemia

Hydroxyurea has proven efficacy in numerous clinical trials as a disease-modifying treatment for patients with sickle cell anemia (SCA) but is currently under-used in clinical practice. To improve the effectiveness of hydroxyurea therapy, efforts should be directed toward broadening the clinical treatment indications, optimizing the daily dosage, and emphasizing the benefits of early and extended treatment. Here, various issues related to hydroxyurea treatment are discussed, focusing on both published evidence and clinical experience. Specific guidance is provided regarding important but potentially unfamiliar aspects of hydroxyurea treatment for SCA, such as escalating to maximum tolerated dose, treating in the setting of cerebrovascular disease, switching from chronic transfusions to hydroxyurea, and using serial phlebotomy to alleviate iron overload. Future research directions to optimize hydroxyurea therapy are also discussed, including personalized dosing based on pharmacokinetic modeling, prediction of fetal hemoglobin responses based on pharmacogenomics, and the risks and benefits of hydroxyurea for non-SCA genotypes and during pregnancy/lactation. Another critical initiative is the introduction of hydroxyurea safely and effectively into global regions that have a high disease burden of SCA but limited resources, such as sub-Saharan Africa, the Caribbean, and India. Final considerations emphasize the long-term goal of optimizing hydroxyurea therapy, which is to help treatment become accepted as standard of care for all patients with SCA.

Optimizing hydroxyurea therapy for sickle cell anemia

Hydroxyurea has proven efficacy in numerous clinical trials as a disease-modifying treatment for patients with sickle cell anemia (SCA) but is currently under-used in clinical practice. To improve the effectiveness of hydroxyurea therapy, efforts should be directed toward broadening the clinical treatment indications, optimizing the daily dosage, and emphasizing the benefits of early and extended treatment. Here, various issues related to hydroxyurea treatment are discussed, focusing on both published evidence and clinical experience. Specific guidance is provided regarding important but potentially unfamiliar aspects of hydroxyurea treatment for SCA, such as escalating to maximum tolerated dose, treating in the setting of cerebrovascular disease, switching from chronic transfusions to hydroxyurea, and using serial phlebotomy to alleviate iron overload. Future research directions to optimize hydroxyurea therapy are also discussed, including personalized dosing based on pharmacokinetic modeling, prediction of fetal hemoglobin responses based on pharmacogenomics, and the risks and benefits of hydroxyurea for non-SCA genotypes and during pregnancy/lactation. Another critical initiative is the introduction of hydroxyurea safely and effectively into global regions that have a high disease burden of SCA but limited resources, such as sub-Saharan Africa, the Caribbean, and India. Final considerations emphasize the long-term goal of optimizing hydroxyurea therapy, which is to help treatment become accepted as standard of care for all patients with SCA.

Systematic and Meta-Analytic Review: Medication Adherence Among Pediatric Patients With Sickle Cell Disease

OBJECTIVE

To provide a comprehensive summary (systematic review) of medication adherence rates by assessment method and medication type for pediatric patients with sickle cell disease (SCD), as well as identify important correlates for future research.

METHODS

Articles assessing medication adherence and published between 1982 and February 2015 (n = 49) were identified using electronic databases. A meta-analysis of 14 studies examining demographic, medical, and psychosocial factors and medication adherence was conducted.

RESULTS

Adherence rates ranged from 12% to 100% across all medications. Approximately 30% of studies reported associations between adherence and key demographic, medical, and psychosocial correlates. Mean effect sizes were small to moderate (r = .02-.53).

CONCLUSIONS

The wide range of adherence rates reported in the literature may be because of, in part, the use of variable assessment strategies. Future studies examining pediatric SCD adherence should incorporate key correlates with the goal of replication.

Hydroxyurea therapy for sickle cell anemia

INTRODUCTION

Sickle cell anemia (SCA) is a severe, inherited hemoglobin disorder affecting 100,000 persons in the US and millions worldwide. Hydroxyurea, a once daily oral medication, has emerged as the primary disease-modifying therapy for SCA. The accumulated body of evidence over 30 years demonstrates that hydroxyurea is a safe and effective therapy for SCA, but hydroxyurea remains underutilized for a variety of reasons.

AREAS COVERED

In this review, we summarize the available evidence regarding the pharmacology, clinical, and laboratory benefits, and safety of hydroxyurea therapy for the treatment of SCA. The purpose of this review is to provide the reader a comprehensive understanding of hydroxyurea and to reinforce the fact that hydroxyurea is a safe and effective medication for the treatment of SCA.

EXPERT OPINION

In our opinion, hydroxyurea therapy should be considered standard-of-care for SCA, representing an essential component of patient management. Early initiation and broader use of hydroxyurea will alter the natural history of SCA, so affected children can live longer and healthier lives. In addition, hydroxyurea use should be extended to low-resource settings such as sub-Saharan Africa, where the burden of SCA and the need for hydroxyurea is arguably the greatest.

Therapeutic phlebotomy is safe in children with sickle cell anaemia and can be effective treatment for transfusional iron overload

Serial phlebotomy was performed on sixty children with sickle cell anaemia, stroke and transfusional iron overload randomized to hydroxycarbamide in the Stroke With Transfusions Changing to Hydroxyurea trial. There were 927 phlebotomy procedures with only 33 adverse events, all of which were grade 2. Among 23 children completing 30 months of study treatment, the net iron balance was favourable (-8·7 mg Fe/kg) with significant decrease in ferritin, although liver iron concentration remained unchanged. Therapeutic phlebotomy was safe and well-tolerated, with net iron removal in most children who completed 30 months of protocol-directed treatment.

Magnetic resonance imaging/angiography and transcranial Doppler velocities in sickle cell anemia: results from the SWiTCH trial

The Stroke With Transfusions Changing to Hydroxyurea (SWiTCH) trial compared standard (transfusions/chelation) to alternative (hydroxyurea/phlebotomy) treatment to prevent recurrent stroke and manage iron overload in children chronically transfused over 7 years before enrollment. Standardized brain magnetic resonance imaging/magnetic resonance angiography (MRA) and transcranial Doppler (TCD) exams were performed at entry and exit, with a central blinded review. A novel MRA vasculopathy grading scale demonstrated frequent severe baseline left/right vessel stenosis (53%/41% ≥Grade 4); 31% had no vessel stenosis on either side. Baseline parenchymal injury was prevalent (85%/79% subcortical, 53%/37% cortical, 50%/35% subcortical and cortical). Most children had low or uninterpretable baseline middle cerebral artery TCD velocities, which were associated with worse stenoses (incidence risk ratio [IRR] = 5.1, P ≤ .0001 and IRR = 4.1, P < .0001) than normal velocities; only 2% to 12% had any conditional/abnormal velocity. Patients with adjudicated stroke (7) and transient ischemic attacks (19 in 11 standard/8 alternative arm subjects) had substantial parenchymal injury/vessel stenosis. At exit, 1 child (alternative arm) had a new silent infarct, and another had worse stenosis. SWiTCH neuroimaging data document severe parenchymal and vascular abnormalities in children with SCA and stroke and support concerns about chronic transfusions lacking effectiveness for preventing progressive cerebrovascular injury. The novel SWiTCH vasculopathy grading scale warrants validation testing and consideration for use in future clinical trials. This trial was registered at www.clinicaltrials.gov as #NCT00122980.

Cerebrovascular complications in children with sickle cell disease

Cerebrovascular accidents were until recently responsible for much mortality and morbidity in children with sickle cell disease; the likelihood of a child with HbSS having a stroke was 11% before age 20 years, with a peak incidence of ischemic stroke between 2 and 5 years of age, and of hemorrhagic strokes between 20 and 29 years of age. Vessels occlusion is likely initiated by intimal proliferation and amplified by inflammation, excessive adhesion of cells to activated endothelium, hypercoagulable state, and vascular tone dysregulation. Silent infarcts may occur and are associated with decreased cognitive functions. Transcranial Doppler ultrasonography (TCD) was more recently demonstrated able to achieve early detection of the children at high risk for clinical strokes. A randomized study demonstrated that a first stroke may be prevented by monthly transfusion in children with abnormal TCD, leading to a recommendation for annual TCD screening of children aged between 2 and 16 years and monthly transfusion for those with abnormal results. In children who have had a first stroke, the risk of recurrence is more than 50% and is greatly reduced by chronic transfusion, although not completely abolished. Hematopoietic stem cell transplant is indicated in children with cerebral vasculopathy who have an HLA-identical sibling.

Neurologic complications of sickle cell disease

Sickle cell disease (SCD) is a group of genetic blood disorders that vary in severity, but the most severe forms, primarily homozygous sickle cell anemia, are associated with neurologic complications. Over the last 90 years it has become established that some patients will develop severe arterial disease of the intracranial brain arteries and suffer brain infarction. Smaller infarctions and brain atrophy may also be seen and over time there appear to be negative cognitive effects in some patients, with or without abnormal brain imaging. Focal mononeuropathies and pneumococcal meningitis are also more common in these patients. Brain infarction in children can largely be prevented screening children beginning at age 2 years and instituting regular blood transfusion when the Doppler indicates high stroke risk (>200cm/sec). Iron overload and the uncertain duration of transfusion are disadvantages but overall this approach, tested in a randomized clinical trial, reduced first stroke by over 90%. Secondary stroke prevention has not been subjected to a randomized controlled trial except for one recently stopped comparison of regular transfusions compared to hydroxuyrea (results favored transfusion). The usual stroke prevention agents (such as aspirin or warfarin) have not been rigorously tested. Magnetic resonance imaging and positron emission tomography give evidence of subtle and sometimes overt brain injury due to stroke in many adults, but a preventive strategy for adults with SCD has not been developed. Bone marrow transplantation is the only cure, but some non-neurologic symptoms can be controlled in adults with hydroxuyrea.

Blood transfusion for preventing primary and secondary stroke in people with sickle cell disease

BACKGROUND

In sickle cell disease, a common inherited haemoglobin disorder, abnormal haemoglobin distorts red blood cells, causing anaemia, vaso-occlusion and dysfunction in most body organs. Without intervention, stroke affects around 10% of children with sickle cell anaemia (HbSS) and recurrence is likely. Chronic blood transfusion dilutes the sickled red blood cells, reducing the risk of vaso-occlusion and stroke. However, side effects can be severe.

OBJECTIVES

To assess risks and benefits of chronic blood transfusion regimens in people with sickle cell disease to prevent first stroke or recurrences.

SEARCH METHODS

We searched the Cochrane Cystic Fibrosis and Genetic Disorders Group Trials Register, comprising references identified from comprehensive electronic database searches and handsearches of relevant journals and conference proceedings.Date of the latest search of the Group's Haemoglobinopathies Trials Register: 28 January 2013.

SELECTION CRITERIA

Randomised and quasi-randomised controlled trials comparing blood transfusion as prophylaxis for stroke in people with sickle cell disease to alternative or no treatment.

DATA COLLECTION AND ANALYSIS

Both authors independently assessed the risk of bias of the included trials and extracted data.

MAIN RESULTS

Searches identified three eligible randomised trials (n = 342). The first two trials addressed the use of chronic transfusion to prevent primary stroke; the third utilized the drug hydroxycarbamide (hydroxyurea) and phlebotomy to prevent both recurrent (secondary) stroke and iron overload in patients who had already experienced an initial stroke. In the first trial (STOP) a chronic transfusion regimen for maintaining sickle haemoglobin lower than 30% was compared with standard care in 130 children with sickle cell disease judged (through transcranial Doppler ultrasonography) as high-risk for first stroke. During the trial, 11 children in the standard care group suffered a stroke compared to one in the transfusion group, odds ratio 0.08 (95% confidence interval 0.01 to 0.66). This meant the trial was terminated early. The transfusion group had a high complications rate, including iron overload, alloimmunisation, and transfusion reactions. The second trial (STOP II) investigated risk of stroke when transfusion was stopped after at least 30 months in this population. The trial closed early due to a significant difference in risk of stroke between participants who stopped transfusion and those who continued as measured by reoccurrence of abnormal velocities on Doppler examination or the occurrence of overt stroke in the group that stopped transfusion. The third trial (SWiTCH) was a non-inferiority trial comparing transfusion and iron chelation (standard management) with hydroxyurea and phlebotomy (alternative treatment) with the combination endpoint of prevention of stroke recurrence and reduction of iron overload. This trial was stopped early after enrolment and follow up of 133 children because of analysis showing futility in reaching the composite primary endpoint. The stroke rate (seven strokes on hydroxyurea and phlebotomy, none on transfusion and chelation, odds ratio 16.49 (95% confidence interval 0.92 to 294.84)) was within the non-inferiority margin, but the liver iron content was not better in the alternative arm.

AUTHORS' CONCLUSIONS

The STOP trial demonstrated a significantly reduced risk of stroke in participants with abnormal transcranial Doppler ultrasonography velocities receiving regular blood transfusions. The follow-up trial (STOP 2) indicated that individuals may revert to former risk status if transfusion is discontinued. The degree of risk must be balanced against the burden of chronic transfusions. The combination of hydroxyurea and phlebotomy is not as effective as "standard" transfusion and chelation in preventing secondary stroke and iron overload. Ongoing multicentre trials are investigating the use of chronic transfusion to prevent silent infarcts, the use of hydroxyurea as an alternative to transfusion in children with abnormal transcranial Doppler ultrasonography velocities, and the use of hydroxyurea to prevent conversion of transcranial Doppler ultrasonography velocities from conditional (borderline) to abnormal values.

Pain and other non-neurological adverse events in children with sickle cell anemia and previous stroke who received hydroxyurea and phlebotomy or chronic transfusions and chelation: results from the SWiTCH clinical trial

To compare the non-neurological events in children with sickle cell anemia (SCA) and previous stroke enrolled in SWiTCH. The NHLBI-sponsored Phase III multicenter randomized clinical trial stroke with transfusions changing to hydroxyurea (SWiTCH) (ClinicalTrials.gov NCT00122980) compared continuation of chronic blood transfusion/iron chelation to switching to hydroxyurea/phlebotomy for secondary stroke prevention and management of iron overload. All randomized children were included in the analysis (intention to treat). The Fisher's Exact test was used to compare the frequency of subjects who experienced at least one SCA-related adverse event (AE) or serious adverse event (SAE) in each arm and to compare event rates. One hundred and thirty three subjects, mean age 13 ± 3.9 years (range 5.2-19.0 years) and mean time of 7 years on chronic transfusion at study entry, were randomized and treated. Numbers of subjects experiencing non-neurological AEs were similar in the two treatment arms, including SCA-related events, SCA pain events, and low rates of acute chest syndrome and infection. However, fewer children continuing transfusion/chelation experienced SAEs (P = 0.012), SCA-related SAEs (P = 0.003), and SCA pain SAEs (P = 0.016) as compared to children on the hydroxyurea/phlebotomy arm. The timing of phlebotomy did not influence SAEs. Older age at baseline predicted having at least 1 SCA pain event. Patients with recurrent neurological events during SWiTCH were not more likely to experience pain. In children with SCA and prior stroke, monthly transfusions and daily iron chelation provided superior protection against acute vaso-occlusive pain SAEs when compared to hydroxyurea and monthly phlebotomy.

Current management of sickle cell anemia

Proper management of sickle cell anemia (SCA) begins with establishing the correct diagnosis early in life, ideally during the newborn period. The identification of affected infants by neonatal screening programs allows early initiation of prophylactic penicillin and pneumococcal immunizations, which help prevent overwhelming sepsis. Ongoing education of families promotes the early recognition of disease-released complications, which allows prompt and appropriate medical evaluation and therapeutic intervention. Periodic evaluation by trained specialists helps provide comprehensive care, including transcranial Doppler examinations to identify children at risk for primary stroke, plus assessments for other parenchymal organ damage as patients become teens and adults. Treatment approaches that previously highlighted acute vaso-occlusive events are now evolving to the concept of preventive therapy. Liberalized use of blood transfusions and early consideration of hydroxyurea treatment represent a new treatment paradigm for SCA management.

National trends in incidence rates of hospitalization for stroke in children with sickle cell disease

BACKGROUND

The success of primary stroke prevention for children with sickle cell disease (SCD) throughout the United States is unknown. Therefore, we aimed to generate national incidence rates of hospitalization for stroke in children with sickle cell disease (SCD) before and after publication of the Stroke Prevention Trial in Sickle Cell Anemia (STOP trial) in 1998.

PROCEDURE

We performed a retrospective trend analysis of the 1993-2009 Nationwide Inpatient Sample and Kids' Inpatient Databases. Hospitalizations for SCD patients 0-18 years old with stroke were identified by ICD-9CM code. The primary outcome, the trend in annual incidence rate of hospitalization for stroke in children with SCD, was analyzed by linear regression. Incidence rates of hospitalization for stroke before and after 1998 were compared by the Wilcoxon rank-sum test.

RESULTS

From 1993 to 2009, 2,024 hospitalizations were identified for stroke. Using the mean annual incidence rate of hospitalization for stroke from 1993 to 1998 as the baseline, the rate decreased from 1993 to 2009 (point estimate = -0.022/100 patient years [95% CI, -0.039, -0.005], P = 0.027). The mean annual incidence rate of hospitalization stroke decreased by 45% from 0.51 per 100 patient years in 1993-1998 to 0.28 per 100 patient years in 1999-2009 (P = 0.008). Total hospital days and charges attributed to stroke also decreased by 45% and 24%, respectively.

CONCLUSIONS

After publication of the STOP trial and hydroxyurea licensure in 1998, the incidence of hospitalization for stroke in children with SCD decreased across the United States, suggesting that primary stroke prevention has been effective nationwide, but opportunity for improvement remains.

Brazilian Guidelines for transcranial doppler in children and adolescents with sickle cell disease

BACKGROUND

Sickle cell disease is the most common monogenic hereditary disease in Brazil. Although strokes are one of the main causes of morbidity and mortality in these patients, the use of transcranial Doppler to identify children at risk is not universally used.

OBJECTIVE

To develop Brazilian guidelines for the use of transcranial Doppler in sickle cell disease children and adolescents, so that related health policies can be expanded, and thus contribute to reduce morbidity and mortality.

METHODS

The guidelines were formulated in a consensus meeting of experts in transcranial Doppler and sickle cell disease. The issues discussed were previously formulated and scientific articles in databases (MEDLINE, SciELO and Cochrane) were carefully analyzed. The consensus for each question was obtained by a vote of experts on the specific theme.

RESULTS

Recommendations were made, including indications for the use of transcranial Doppler according to the sickle cell disease genotype and patients age; the necessary conditions to perform the exam and its periodicity depending on exam results; the criteria for the indication of blood transfusions and iron chelation therapy; the indication of hydroxyurea; and the therapeutic approach in cases of conditional transcranial Doppler.

CONCLUSION

The Brazilian guidelines on the use of transcranial doppler in sickle cell disease patients may reduce the risk of strokes, and thus reduce the morbidity and mortality and improve the quality of life of sickle cell disease patients.

Transfusion practices in the management of sickle cell disease: a survey of Florida hematologists/oncologists

The purpose of this study was to characterize transfusion practices in the management of sickle cell disease and to identify factors attributing to differences in prescribing practices among Florida hematologists/oncologists. A cross-sectional study was performed in 2005-2006 utilizing a mail survey. The survey instrument addressed practice characteristics, sickle cell patient populations, transfusion settings, indications and techniques, red blood cell phenotype specifications/modifications, use of practice guidelines, and educational resource utilization. One hundred fifty two physicians (75% adult-oriented, 25% pediatric) completed the survey. Non-academic practice settings (78 %) were the primary location. Pediatric practices had a larger percentage of patients with overt strokes, and receiving hydroxyurea therapy than adult-oriented practices. The majority of survey respondents did not request limited phenotypically matched red blood cells on a routine basis. The majority of pediatric practices (60%) had individually defined transfusion practice guidelines in contrast to 8% of adult-oriented practices. There were statistically significant differences for pediatric and adult-oriented practices in managing certain acute and chronic transfusion indications. Analysis of clinical vignette data revealed variation among hematologists/oncologists in the transfusion management of common clinical scenarios. The study underscores the need for the development and dissemination of comprehensive sickle cell transfusion guidelines and protocols.

Hydroxyurea for the treatment of sickle cell disease: efficacy, barriers, toxicity, and management in children

Hydroxyurea is the only approved medication in the United States for the treatment of sickle cell anemia (HbSS) and is widely used in children despite an indication limited to adults. We review the evidence of efficacy and safety in children with reference to pivotal adult studies. This evidence and expert opinion form the basis for recommended guidelines for the use of hydroxyurea in children including indications, dosing, therapeutic and safety monitoring, and interventions to improve adherence. However, there are substantial gaps in our knowledge to be addressed by on-going and planned studies in children.

Stroke With Transfusions Changing to Hydroxyurea (SWiTCH)

Stroke is a devastating complication of sickle cell anemia (SCA) with high recurrence if untreated. Chronic transfusions reduce recurrent strokes but have associated morbidities including iron overload. Stroke With Transfusions Changing to Hydroxyurea (SWiTCH) was a multicenter phase 3 randomized trial comparing standard treatment (transfusions/chelation) to alternative treatment (hydroxyurea/phlebotomy) for children with SCA, stroke, and iron overload. SWiTCH was a noninferiority trial with a composite primary end point, allowing an increased stroke risk but requiring superiority for removing iron. Subjects on standard treatment received monthly transfusions plus daily deferasirox iron chelation. Subjects on alternative treatment received hydroxyurea plus overlap transfusions during dose escalation to maximum tolerated dose (MTD), followed by monthly phlebotomy. Subjects on standard treatment (N = 66) maintained 30% sickle hemoglobin (HbS) and tolerated deferasirox at 28.2 ± 6.0 mg/kg/d. Subjects on alternative treatment (N = 67) initiated hydroxyurea and 60 (90%) reached MTD at 26.2 ± 4.9 mg/kg/d with 29.1% ± 6.7% fetal hemoglobin (HbF). Adjudication documented no strokes on transfusions/chelation but 7 (10%) on hydroxyurea/phlebotomy, still within the noninferiority stroke margin. The National Heart, Lung, and Blood Institute closed SWiTCH after interim analysis revealed equivalent liver iron content, indicating futility for the composite primary end point. Transfusions and chelation remain a better way to manage children with SCA, stroke, and iron overload.

What Is the Evidence for Using Hydroxyurea for Secondary Stroke Prevention?

A 10-year-old male patient with hemoglobin SS suffered a stroke at 7 years of age and was initially transfused at the time of presentation to lower the hemoglobin S concentration to < 30%. You are asked by the family if their child can be treated with oral hydroxyurea rather than monthly transfusions for the secondary prevention of strokes.

Stroke With Transfusions Changing to Hydroxyurea (SWiTCH): a phase III randomized clinical trial for treatment of children with sickle cell anemia, stroke, and iron overload

BACKGROUND

Stroke occurs in 5-10% of children with sickle cell anemia (SCA) and has a high (>50%) risk of recurrence without therapy. Chronic monthly erythrocyte transfusions effectively prevent recurrent stroke, but their long-term use is limited by serious side effects, including iron overload. An alternative to transfusion for secondary stroke prevention in SCA is needed, especially one that also improves the management of iron overload.

METHODS

Stroke With Transfusions Changing to Hydroxyurea (SWiTCH) is an NHLBI-sponsored Phase III multicenter randomized controlled clinical trial for children with SCA, stroke, and iron overload (NCT00122980). The primary goal of SWiTCH is to compare 30 months of alternative therapy (hydroxyurea and phlebotomy) with standard therapy (transfusions and chelation) for the prevention of secondary stroke and reduction of transfusional iron overload.

DISCUSSION

SWiTCH has several distinctive study features including novel methodological and design components: (1) composite primary endpoint including both stroke recurrence rate and iron burden; (2) non-inferiority design with an "acceptable" increased stroke risk; (3) transfusion goals based on current academic community practices; (4) special oversight for the enrollment and randomization process; (5) overlap treatment period within the alternative treatment arm; (6) masking of the overall trial Principal Investigator to treatment results; (7) inclusive independent stroke adjudication process for all suspected new neurological events; and (8) periodic therapeutic phlebotomy program to alleviate iron overload.

CONCLUSION

Investigation of alternative treatments in SWiTCH could lead to changes in the management of cerebrovascular disease for selected patients with SCA, stroke, and iron overload.

Stroke recurrence in children with sickle cell disease treated with hydroxyurea following first clinical stroke

Chronic transfusion therapy is the treatment of choice for preventing stroke recurrence in children with sickle cell disease (SCD). The majority of children affected by this devastating complication live in the developing world where access to regular blood transfusions may be impractical. Since 2000, in the absence of regular blood supplies, all children at the Sickle Cell Unit who had experienced a first clinical stroke were offered hydroxyurea (HU) as the only intervention to prevent stroke recurrence. Forty-four children were identified as having experienced a first clinical stroke between January 1, 2000 and September 30, 2009; one died at that presentation. Forty-three children were therefore followed for 111 person-years, of whom 10 (23.3%) agreed to start HU. Only one child in the HU group, incidence rate 2/100 person-years, had clinical stroke recurrence, compared to 20/33 in the non-HU group, incidence rate 29/100 person-years (Hazard ratio (HR) 9.4 [95% Confidence interval (CI): 1.3-70.6]; P = 0.03). When the groups were compared, in the non-HU group, four died (vs. zero), 13 (53% vs. 10%) had moderate-severe physical disability (P = 0.017), and 12 (44% vs. 20%) required special education or were too disabled to attend school. Our data support the role of HU as a useful intervention for prevention of stroke recurrence in SCD when transfusion programs are not available or practical.

Current concepts in the management of stroke in children with sickle cell disease

Stroke is the most significant complication of sickle cell disease (SCD) in children with the potential for major morbidity and mortality. The recent two decades have witnessed tremendous advancements in understanding the pathophysiology of stroke, risk stratification of children and the role of timely preventative interventions. The aetiopathogenesis, types of stroke and specific risk factors are reviewed here with special emphasis on the role of transcranial Doppler ultrasonogram in the early identification of at-risk children. Published studies on primary and secondary prevention of stroke in children with SCD are analysed with respect to the levels of evidence, in favour of preventative and therapeutic strategies. The roles of the neurologist and the neurosurgeon are highlighted.

Current strategies for the management of children with sickle cell disease

Children with sickle cell disease may present to doctors anywhere in the world. In developed countries, neonatal screening allows early identification and management of the disease, mostly through daily antibioprophylaxis, immunizations and education of the parents. Stroke prevention relies on the detection of high-risk patients by annual transcranial Doppler ultrasonography from 2 to 16 years of age. Annual check-ups aim to detect early organ deficiencies. The most frequent complications are pain, infections and acute anemia; they may occur in combination. Approximately 10% of children have severe sickle cell disease that may require chronic blood transfusion, hydroxyurea or hematopoietic stem cell transplantation. Comprehensive management programs have dramatically increased survival, and most patients now reach adulthood.

Long-term results using hydroxyurea/phlebotomy for reducing secondary stroke risk in children with sickle cell anemia and iron overload

Children with sickle cell anemia (SCA) and a primary overt stroke are at high risk of recurrent (secondary) stroke. Chronic transfusion therapy dramatically reduces but does not eliminate this high risk, and inevitably results in transfusion-related hemosiderosis. We previously reported the use of hydroxyurea/phlebotomy as an alternative to transfusions to reduce the risk of secondary stroke and improve management of iron overload in 35 children with SCA. To report long-term results, we retrospectively reviewed clinical and laboratory data through October 2008. With a median of 5.6 years and total of 219 patient-years of follow-up, 10 of 35 patients (29%) had recurrent stroke after switching to hydroxyurea; seven were previously reported and three new strokes occurred during extended follow-up. The overall secondary stroke event rate was 4.6 per 100 patient-years. Children on hydroxyurea received serial phlebotomy and had lower mean serum ferritin values than children on transfusions (591 ng/mL vs. 3410 ng/mL, P = 0.02). In this cohort, long-term hydroxyurea treatment reduced but did not eliminate the risk of stroke recurrence and, uniquely, allowed phlebotomy to reduce iron overload. Long-term assessments of this therapy should evaluate risk factors for secondary stroke and assessments of hemosiderosis, neurocognitive outcome, and health-related quality of life.

Diagnosis and management of pediatric arterial ischemic stroke

Pediatric stroke is among the top 10 causes of death in children and an important cause of chronic morbidity, with an incidence of 3.3/100,000 children/year. Risk factors associated with stroke in children include cardiac diseases, hematologic and vascular disorders, and infection. Clinical presentation varies depending on age, underlying cause, and stroke location. Antithrombotics and anticoagulants are used in the treatment of pediatric stroke; however, there are no established guidelines for the use of these agents in children. In this article we review the cause, pathophysiology, clinical presentation, diagnosis, acute management, secondary prevention, and outcome of children with stroke. The approach to patients with sickle cell disease and Moyamoya disease is also discussed. Up to date studies to determine the optimal acute treatment of childhood stroke and secondary prevention and risk factor modification are critically needed.

How I use hydroxyurea to treat young patients with sickle cell anemia

Hydroxyurea has many characteristics of an ideal drug for sickle cell anemia (SCA) and provides therapeutic benefit through multiple mechanisms of action. Over the past 25 years, substantial experience has accumulated regarding its safety and efficacy for patients with SCA. Early proof-of-principle studies were followed by prospective phase 1/2 trials demonstrating efficacy in affected adults, then adolescents and children, and more recently infants and toddlers. The phase 3 National Heart, Lung and Blood Institute-sponsored Multicenter Study of Hydroxyurea trial proved clinical efficacy for preventing acute vaso-occlusive events in severely affected adults. Based on this cumulative experience, hydroxyurea has emerged as an important therapeutic option for children and adolescents with recurrent vaso-occlusive events; recent evidence documents sustained long-term benefits with prevention or reversal of chronic organ damage. Despite abundant evidence for its efficacy, however, hydroxyurea has not yet translated into effective therapy for SCA. Because many healthcare providers have inadequate knowledge about hydroxyurea, patients and families are not offered treatment or decline because of unrealistic fears. Limited support for hydroxyurea by lay organizations and inconsistent medical delivery systems also contribute to underuse. Although questions remain regarding its long-term risks and benefits, current evidence suggests that many young patients with SCA should receive hydroxyurea treatment.