1. Among sub-Saharan African children with sickle cell anemia (SCA) treated with hydroxyurea, 5.1% experienced dose-limiting toxic events, well below the protocol-specified allowable rate of 30%.
2. Compared to pretreatment rates, children treated with hydroxyurea had significantly reduced rates of vaso-occlusive pain, infection, malaria, transfusion, and death after one year.
Evidence Rating Level: 1 (Excellent)
Study Rundown: The majority of individuals with SCA are born in sub-Saharan Africa, where public screening and access to quality care are limited. Though hydroxyurea is an established treatment in both children and adults with SCA, data is limited on safety in Africa, where co-existing conditions and malnutrition could impact toxicity thresholds. The prospective Realizing Effectiveness across Continents with Hydroxyurea (REACH) trial was designed to investigate the safety, efficacy, and feasibility of hydroxyurea treatment for children in sub-Saharan Africa with SCA. The primary end point, hematologic dose-limiting toxic effects in the first three months, was well below the protocol-specified safety threshold. Compared to the pretreatment period, one year of treatment with hydroxyurea led to significant increases in hemoglobin and fetal hemoglobin levels and significant decreases in vaso-occlusive pain, malaria and nonmalaria infection, transfusions, and death. Adherence and retention rates were high throughout the trial period. The results emphasize the importance of providing wider access to hydroxyurea for this patient population, where disease burden is the greatest.
This was a large, two-staged, prospective trial with full enrollment retention of participants, high rates of adherence to trial visits and medication use, and nearly 95% retention rate over three years. The trial also importantly demonstrated a significant reduction in rates of malaria, despite a lack of chemoprophylaxis programs at all the clinical sites. Given the lack of randomization and placebo control, the trial was limited in ability to show survival benefits. Additionally, more data is needed to determine if the high adherence can be maintained with less monitoring and to observe for any long-term adverse effects.
In-Depth [prospective cohort]: Children age one to ten completed screening and initiated hydroxyurea treatment (n=606) at four trial sites in sub-Saharan Africa. Enrollment was paused at each site to evaluate the three-month hematologic toxicities among the first 53 children enrolled. Hydroxyurea was initiated at a dose of 15 to 20 mg/kg/day, and after six months was escalated by 2.5 to 5 mg/kg/day every two months to determine a maximum tolerated dose. The primary end point was hematologic dose-limiting toxic effects in the first three months of treatment in the first 133 children enrolled at each site (expected rate of primary end point, 20%; allowable rate, 30%). Additional end points included feasibility (enrollment, retention, and adherence) and benefits (laboratory values, sickle cell-related events, transfusions, and survival).
Among the children who began treatment, 600 (99.0%) completed three months and the overall retention rate at three years was 94.2% (33 children [5.4%] withdrew after initiation). The initial mean dose of hydroxyurea was 17.5±1.8 mg/kg/day and mean maximum tolerated dose was 22.5±4.9 mg/kg/day (range, 18.9±4.2 mg/kg/day in Angola to 25.3±4.8 mg/kg/day in Uganda). The primary end point occurred in 5.1% of children overall and significantly differed across sites, ranging from 0.8% to 8.3% (P=0.01), with a random-effects pooled estimate of 4.5% (95% confidence interval [CI], 2.3% to 8.8%). Significant increases in hemoglobin (mean increase, 1.0 g/dL; 95% confidence interval [CI], 0.8 to 1.0), mean corpuscular volume (mean increase, 13 fl; 95% CI,12 to 13), and fetal hemoglobin levels (mean increase, 12.5%; 95% CI, 11.8 to 13.1) were found after one year of hydroxyurea treatment. The white cell count, absolute neutrophil count, and absolute reticulocyte count all significantly decreased during treatment. There were significant reductions in the incidence of all clinical adverse events (308.4 vs. 170.7 events per 100 patient-years; incidence rate ratio, 0.54; 95% CI, 0.48 to 0.62). Significant reductions in event rates over time were found for all sickle cell-related clinical events: malaria, vaso-occlusive pain, transfusion, acute chest syndrome, and death from any cause.
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