Hydroxyurea appears to be safe and effective in patients 5 to 12 months of age with sickle cell disease and may lead to a more robust response compared with initiating hydroxyurea in older patients, according to a retrospective study published in Pediatric Blood & Cancer.

Researchers evaluated outcomes of 65 patients starting hydroxyurea at less than 5 years of age between January 1, 2008, and December 31, 2016. The patients were divided into 3 different age groups. Cohort 1 included 35 patients (mean age, 7.2 months) who started at less than 1 year of age, cohort 2 included 13 patients (mean age 19.5 months) who started between 1 and 2 years of age, and cohort 3 included 17 patients (mean age, 35.5 months) who started between 2 and 5 years of age. The researchers examined clinical events, laboratory data, and toxicity.

Patients in cohort 1 was found to have higher hemoglobin (P =.0003), higher mean corpuscular volume (P =.0199), and lower absolute reticulocyte count (P =.0304) at 24 months of age compared with patients in cohort 3. The absolute neutrophil count for patients in cohort 1 was lower compared with both older cohorts (P =.0364 for cohort 2, P =.0025 for cohort 3).

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The mean baseline fetal hemoglobin in cohort 1 was 31.5% compared with 19.7% in cohort 2 (P =.002) and 16.5% in cohort 3 (29.1 months; P <.0001). Mean fetal hemoglobin levels remained significantly higher in cohort 1 (29.9%) during the course of the therapy compared with cohort 2 (20.4%; P =.007) and cohort 3 (20.6%; P =.003).

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Patients in cohort 1 also fared better in terms of inpatient care. Overall, patients in cohort 1 experienced fewer hospitalizations, pain crises, and transfusions. The researchers found no difference in toxicity among the 3 groups; aside from 1 patient in cohort 1 who required a decreased dosage of hydroxyurea, no patients in any cohort experienced hematologic toxicity.

The researchers recommended starting hydroxyurea treatment as early as 5 months of age. However, because “neither neurocognitive testing nor brain MRI was routinely obtained,” they cautioned that “safety of hydroxyurea in this very young age group should be viewed with caution in this small, retrospective, single-center study.”


1. Schuchard SB, Lissick JR, Nickel A, et al. Hydroxyurea use in young infants with sickle cell disease [published online February 7, 2019]. Pediatr Blood Cancer. doi: 10.1002/pbc.27650