Introduction. The burden of sickle cell anemia (SCA) is high across the Caribbean, including the Dominican Republic where the morbidity of SCA is substantial due to limited resources. Approximately 10% of affected children will develop primary stroke, with serious medical and neurocognitive sequelae. In the US, transcranial Doppler (TCD) ultrasonography is an effective screening tool to identify children at risk for primary stroke, which then allows preventive therapy with either hydroxyurea or blood transfusions. To date, however, no routine TCD screening and treatment program for stroke prevention has been established in the Dominican Republic. We designed a prospective screening and treatment study (SACRED, NCT02769845) for prevention of primary stroke in children with SCA using open-label hydroxyurea at maximum tolerated dose (MTD).
Methods. Children with SCA between age 3-15 years and receiving medical care at Robert Reid Cabral Children's Hospital in Santo Domingo, Dominican Republic were recruited over a 12-month period. Treatment depended on the baseline TCD examination: children with abnormal time-averaged mean velocities (≥200 cm/sec, high stroke risk) were recommended to receive monthly transfusions for primary stroke prevention, as per standard treatment preferences at the Robert Reid Hospital; those with conditional velocities (170-199 cm/sec, moderate stroke risk) were offered hydroxyurea study treatment unless they were currently receiving chronic transfusions for other clinical indications. Oral open-label hydroxyurea using 500mg capsules was prescribed at fixed-dose (20 mg/kg/day) for 6 months, followed by dose escalation to MTD. TCD examinations were repeated every 6 months, with the main study endpoints being changes in laboratory parameters and TCD velocities after 18 months of study treatment.
Results. A total of 283 children were enrolled with the following baseline TCD velocities: 200 (70.7%) normal, 63 (22.3%) conditional, 11 (3.9%) abnormal, and 9 (3.1%) inadequate velocities. Among 50 children eligible for hydroxyurea study treatment, the average age was 6.8 ± 2.8 years and included 27 males/23 females with evidence of substantial SCA-related morbidity (88% with previous transfusions, 60% with >5 hospitalizations). A total of 48 children initiated hydroxyurea at 20.2 ± 1.2 mg/kg/day, which was maintained for 6 months followed by dose escalation, reaching MTD at 24.1 ± 6.0 mg/kg/day. Laboratory changes from baseline to Month 18 included significant increases in hemoglobin (7.5 ± 0.9 to 8.9 ± 1.3 g/dL, P<0.0001) and fetal hemoglobin (16.4 ± 7.4 to 30.9 ± 13.6%, P<0.0001). Serial TCD examinations revealed a significant decline over the treatment period, with the average TCD velocity decreasing from 180 ± 8 cm/sec at baseline to 159 ± 21 cm/sec at Month 18, P<0.0001. At Month 18, 68% of the originally conditional TCD examinations had reverted to a normal velocity, while only 4% had converted to abnormal velocity. No clinical strokes occurred in the hydroxyurea treatment cohort.
Conclusion. Conditional TCD velocities are common (>20%) in the Dominican Republic, which documents an elevated stroke risk for children with SCA. The SACRED trial established a local TCD screening program and provided open-label hydroxyurea treatment for children with conditional TCD velocities. Hydroxyurea treatment at MTD led to improved hematological parameters, lower TCD velocities, and decreased stroke risk. SACRED represents an important international partnership and prospective collaborative research trial providing capacity building and valuable epidemiological data regarding TCD screening, stroke risk, and hydroxyurea effects for children with SCA. Hydroxyurea at MTD is a suitable treatment to reduce primary stroke risk for children with SCA living in the Dominican Republic or other low-resource settings.
Jeste:Jannsen: Employment. Ware:Novartis: Other: DSMB; Nova Laboratories: Membership on an entity's Board of Directors or advisory committees; CSL Behring: Membership on an entity's Board of Directors or advisory committees; Bristol Myers Squibb: Other: Research Drug Donation; Addmedica: Other: Research Drug Donation; Global Blood Therapeutics: Membership on an entity's Board of Directors or advisory committees; Agios: Membership on an entity's Board of Directors or advisory committees.
Asterisk with author names denotes non-ASH members.