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Hydroxyurea for sickle cell disease: a systematic review for efficacy and toxicity in children
John J Strouse1, Sophie Lanzkron, Mary Catherine Beach
1Department of Pediatrics, Johns Hopkins University School of Medicine, Division of Pediatric Hematology, 720 Rutland Ave, Ross 1125, Baltimore, MD 21205, USA. jstrous1@jhmi.edu
Insights
Hydroxyurea significantly reduces hospitalizations and pain crises in children with sickle cell anemia, increasing hemoglobin levels. While generally safe, long-term toxicity data in pediatric patients remains limited.
Area of Science:
- Pediatric Hematology
- Pharmacology
- Clinical Trials
Background:
- Hydroxyurea is the sole approved medication for adult sickle cell disease.
- No approved drug treatments currently exist for pediatric sickle cell disease.
Purpose of the Study:
- To synthesize existing literature on hydroxyurea's efficacy, effectiveness, and toxicity in pediatric sickle cell disease patients.
- To evaluate the impact of hydroxyurea on clinical outcomes and adverse events in children.
Main Methods:
- Systematic literature review of Medline, Embase, TOXLine, and CINAHL up to June 2007.
- Inclusion of randomized trials, observational studies, and case reports evaluating hydroxyurea in pediatric sickle cell disease.
- Sequential data abstraction and independent quality assessment by two reviewers.
Main Results:
- Hydroxyurea increased fetal hemoglobin (HbF) from 5-10% to 15-20% and modestly increased overall hemoglobin.
- Hospitalizations decreased by 56-87%, and pain crises and neurologic events were reduced in observational studies.
- Common adverse events included reversible neutropenia and mild thrombocytopenia; severe events were rare.
Conclusions:
- Hydroxyurea effectively reduces hospitalizations and increases hemoglobin levels in children with severe sickle cell anemia.
- Evidence for efficacy in other sickle cell disease groups is insufficient.
- Limited long-term studies hinder definitive conclusions on late toxicities in children.
Context:
Hydroxyurea is the only approved medication for the treatment of sickle cell disease in adults; there are no approved drugs for children.
Objective:
Our goal was to synthesize the published literature on the efficacy, effectiveness, and toxicity of hydroxyurea in children with sickle cell disease.
Methods:
Medline, Embase, TOXLine, and the Cumulative Index to Nursing and Allied Health Literature through June 2007 were used as data sources. We selected randomized trials, observational studies, and case reports (English language only) that evaluated the efficacy and toxicity of hydroxyurea in children with sickle cell disease. Two reviewers abstracted data sequentially on study design, patient characteristics, and outcomes and assessed study quality independently.
Results:
We included 26 articles describing 1 randomized, controlled trial, 22 observational studies (11 with overlapping participants), and 3 case reports. Almost all study participants had sickle cell anemia. Fetal hemoglobin levels increased from 5%-10% to 15%-20% on hydroxyurea. Hemoglobin concentration increased modestly (approximately 1 g/L) but significantly across studies. The rate of hospitalization decreased in the single randomized, controlled trial and 5 observational studies by 56% to 87%, whereas the frequency of pain crisis decreased in 3 of 4 pediatric studies. New and recurrent neurologic events were decreased in 3 observational studies of hydroxyurea compared with historical controls. Common adverse events were reversible mild-to-moderate neutropenia, mild thrombocytopenia, severe anemia, rash or nail changes (10%), and headache (5%). Severe adverse events were rare and not clearly attributable to hydroxyurea.
Conclusions:
Hydroxyurea reduces hospitalization and increases total and fetal hemoglobin levels in children with severe sickle cell anemia. There was inadequate evidence to assess the efficacy of hydroxyurea in other groups. The small number of children in long-term studies limits conclusions about late toxicities.
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