ALBERT

Description: Transcranial Doppler (TCD) screening in children with sickle cell anemia (SCA) identifies abnormally elevated cerebral artery flow velocities that confer an elevated risk for primary stroke. Chronic transfusions offer effective stroke prophylaxis in this setting, but must be continued indefinitely and lead to transfusional iron overload. An alternative treatment strategy that offers similar effective protection against primary stroke, and provides control of iron overload, is needed. TCD With Transfusions Changing to Hydroxyurea (TWiTCH, NCT01425307) was an NHLBI-funded Phase III multicenter randomized clinical trial comparing 24-months of standard treatment (transfusions) to alternative treatment (hydroxyurea) in children with SCA and abnormal TCD velocities. All eligible children had received at least 12 months of transfusions. TWiTCH had a non-inferiority trial design; the primary study endpoint was the 24-month TCD velocity obtained from a linear mixed model, controlling for baseline (enrollment) values, with a non-inferiority margin of 15 cm/sec. The transfusion arm maintained children at HbS

Description: Children with sickle cell disease (SCD) and stroke receive chronic transfusions to prevent stroke recurrence. Transfusion risks including infection, erythrocyte allosensitization, and iron overload suggest a need for alternative therapies. We previously used hydroxyurea (HU) and phlebotomy in two young adults with SCD and stroke as an alternative to transfusions. We have now prospectively discontinued transfusions in 16 pediatric patients with SCD and stroke. Reasons to discontinue transfusions included erythrocyte alloantibodies or autoantibodies, recurrent stroke on transfusions, iron overload, noncompliance, and deferoxamine allergy. HU was started at 15 mg/kg/d and escalated to 30 mg/kg/d based on hematologic toxicity. Patients with iron overload underwent phlebotomy. The children have been off transfusions 22 months, (range, 3 to 52 months). Their average HU dose is 24.9 ± 4.2 mg/kg/d, hemoglobin concentration is 9.4 ± 1.3 g/dL, and mean corpuscular volume (MCV) is 112 ± 9 fL. Maximum percentage fetal hemoglobin (%HbF) is 20.6% ± 8.0% and percentage HbF-containing erythrocytes (%F cells) is 79.3% ± 14.7%. Fourteen patients underwent phlebotomy with an average of 8,993 mL (267 mL/kg) removed. Serum ferritin has decreased from 2,630 to 424 ng/mL, and 4 children have normal ferritin values. Three patients (19%) had neurological events considered recurrent stroke, each 3 to 4 months after discontinuing transfusions, but before maximal HU effects. These preliminary data suggest some children with SCD and stroke may discontinue chronic transfusions and use HU therapy to prevent stroke recurrence. Phlebotomy is well-tolerated and significantly reduces iron overload. Modifications in HU therapy to raise HbF more rapidly might increase protection against stroke recurrence.

Description: Introduction: The multicenter phase 3 randomized clinical trial TCD With Transfusions Changing to Hydroxyurea (TWiTCH, NCT01425307) investigated whether hydroxyurea could maintain TCD velocities and prevent stroke in children with sickle cell anemia and abnormal TCD velocities. The trial was stopped early after reaching the primary endpoint, when the average TCD velocity in the alternative (hydroxyurea) arm was found to be non-inferior and even slightly better (138 versus 143 cm/sec) than the standard (transfusion) arm. A planned secondary analysis was to determine the variation in serial TCD velocity measurements for individual study participants, to document the normal TCD velocity fluctuations that occur and to inform the need for frequent TCD evaluations in this clinical setting. Methods: All TCD examinations collected in TWiTCH were analyzed for the maximum time-averaged mean velocity (TAMV) measured in the main intracranial arteries. TCD studies were performed by certified examiners using identical non-imaging instruments, no more than one week before a scheduled transfusion or phlebotomy procedure. Measurements on the index side, defined as the cerebral hemisphere with the higher mean arterial velocity at baseline assessment, were used for these statistical analyses. TCD values were analyzed according to four phases of the trial: (1) screening with three monthly TCD examinations performed at Weeks -8, -4, and 0 before randomization; (2) initial treatment period (hydroxyurea dose escalation with overlap transfusions or transfusions only) with three quarterly TCD measurements at Weeks 12, 24, and 36; (3) steady-state treatment period (hydroxyurea only or transfusions only) with four quarterly TCD measurements at Weeks 48, 60, 72, and 84; and (4) study exit with three monthly TCD examinations performed at Weeks 96, 100, and 104 or during the accelerated close-out period. The within-patient variance and standard deviation of the TAMV values were found using a linear mixed model, which was calculated using SAS Version 9.3. Results: TAMV measurements on the index side from 1458 TCD examinations on 121 randomized patients formed the overall dataset. TAMV values ≥170 cm/sec were identified in 140 measurements on 40 children (9.6% of TCD values) and exceeded 200 cm/sec in 1.8% of examinations (26 values, 8 children) during the study treatment phase. The within-patient TCD variation, representing fluctuation of repeated TCD measurements in the same study participant, was 12.0 cm/sec for the entire cohort during the initial screening phase (363 TCD measurements). In the initial treatment phase, TCD variation in the hydroxyurea arm (180 values, 60 children) was 10.5 cm/sec, similar to 10.2 cm/sec on the transfusion arm (183 values, 61 children). In the steady-state treatment phase, the TCD variation in the hydroxyurea arm was 10.2 cm/sec (207 values, 57 children), compared to 12.3 cm/sec on the transfusion arm (212 values, 58 children). In the final exit phase, TCD variation in the hydroxyurea arm was 9.8 cm/sec (155 values, 58 children), similar to 10.2 cm/sec on the standard arm (155 values, 57 children). TCD variation was greater with higher baseline TCD velocity and shorter transfusion duration, but was not affected by age or gender. For example, participants with baseline TCD velocity of

Description: Introduction: TCD with Transfusions Changing toHydroxyurea (TWiTCH Clinical Trials.gov NCT01425307), an NHLBI-sponsored multicenter trial, compared transfusion pluschelation (Standard Arm) tohydroxyurea (HU) plus phlebotomy (Alternative Arm) in children with sickle cell disease at high risk for stroke. Alternative arm patients underwent serial phlebotomy (10mL/kg, maximum 500mL) every 4 weeks after reaching maximal tolerated dose (MTD) of HU and discontinuing transfusions. Changes in liver iron concentration (dLIC), measured as mg Fe per gram dry weight liver, by both MRI R2 (FerriScan) and R2* were key secondary outcome measures. R2 and R2* are two, different MRI techniques that exploit the magnetic properties of tissue iron to estimate iron concentration. We previously reported significant differences between the two approaches at the baselinetimepoint. The purpose of this investigation was to determine the limits of agreement between measurements ofdLIC over a period of one year by R2 and R2* methods in both arms of the study. Methods: MRI R2 and R2* data were collected prior to randomization, and after 1 year (midpoint) and 2 years of therapy (study exit). dLIC between baseline to midpoint and midpoint to study completion was calculated for both R2 and R2* LIC values. Since LIC measurement variability increases with iron burden, each dLIC pair (R2 and R2*) were normalized to the patients iron burden at the start of the observation interval. That is, dLIC from baseline to midpoint was normalized to baseline LIC, while dLIC from midpoint to study end was normalized to midpoint LIC. The geometric mean of LICR2 and LICR2* was used to represent the baseline and midpoint LIC. Bland Altman analysis was performed on measurements of the percent change of dLICR2 and dLICR2* to determine the limits of agreement between the two techniques. Results: R2 measurements were performed in 104 patients at baseline, 94 at midpoint and 99 at study end, while R2* measurements were performed in 101, 87, and 89 patients, respectively. However, missing data limited Bland Altman comparisons ofdLIC to 74 patients between baseline to midpoint and 69 patients from midpoint to study end. Figure 1 (left) plots the measureddLIC using R2 (vertical axis) against the measureddLIC change by R2* (horizontal axis) for the Standard Arm participants. Dots represent LIC change over the first year and open circles represent LIC changes over the second year. The dotted line represents perfect agreement. Figure 1 (right) demonstrates the corresponding relationship for the patients in the Alternative Arm. Although the alternative arm appears to have greater disagreement, this represents an artifactcause by the transient increases in LIC that occurred as patients bridged from standard to alternative therapy. Iron chelationwas stopped when patients began hydroxyureabut patients required an overlap period of transfusions for stroke prophylaxis. Figure 2 demonstrates the difference in dLIC measured by R2 and R2*, expressed as a percentage of starting LIC, plotted against the starting LIC value. The standard arm (open circles) and alternative arms (dots) completely overlap. 95% limits of agreement between the two measures ofdLIC were -45.7% to 63.7% (light lines). At LIC values 〉 8.3 mg/g,dLIC predicted by R2 was larger than predicted by R2*, while the converse was true for LIC values below 8.3 mg/g, similar to our published baseline findings for LIC measurements. Conclusions: LIC by R2 and R2* tracked one another closely over time in patients in both study arms. These data indicate that either technique can be used with confidence to monitor patients on iron removal therapy (chelation or phlebotomy), but that the techniques should not be interchanged. Figure 1 Figure 1. Figure 2 Figure 2. Disclosures Wood: Vifor: Consultancy; Ionis Pharmaceuticals: Consultancy; Vifor: Consultancy; Biomed Informatics: Consultancy; World Care Clinical: Consultancy; Ionis Pharmaceuticals: Consultancy; World Care Clinical: Consultancy; AMAG: Consultancy; AMAG: Consultancy; Celgene: Consultancy; Celgene: Consultancy; Biomed Informatics: Consultancy; Apopharma: Consultancy; Apopharma: Consultancy. St Pierre:Resonance Health: Consultancy, Equity Ownership. Piccone:Novartis: Other: Speaker. Hankins:Novartis: Research Funding. Rogers:Apopharma: Consultancy. Ware:Bayer Pharmaceuticals: Consultancy; Global Blood Therapeutics: Consultancy; Biomedomics: Research Funding; Addmedica: Research Funding; Nova Laboratories: Consultancy; Bristol Myers Squibb: Research Funding.

Description: Hydroxyurea has hematologic and clinical efficacy in sickle cell anemia (SCA), but its effects on transcranial Doppler (TCD) flow velocities remain undefined. Fifty-nine children initiating hydroxyurea therapy for clinical severity had pretreatment baseline TCD measurements; 37 with increased flow velocities (≥ 140 cm/s) were then enrolled in an institutional review board (IRB)–approved prospective phase 2 trial with TCD velocities measured at maximum tolerated dose (MTD) and one year later. At hydroxyurea MTD (mean ± 1 SD = 27.9 ± 2.7 mg/kg per day), significant decreases were observed in the right middle cerebral artery (MCA) (166 ± 27 cm/s to 135 ± 27 cm/s, P 〈 .001) and left (MCA) (168 ± 26 cm/s to 142 ± 27 cm/s, P 〈 .001) velocities. The magnitude of TCD velocity decline was significantly correlated with the maximal baseline TCD value. At hydroxyurea MTD, 14 of 15 children with conditional baseline TCD values improved, while 5 of 6 with abnormal TCD velocities whose families refused transfusions became less than 200 cm/s. TCD changes were sustained at follow-up. These prospective data indicate that hydroxyurea can significantly decrease elevated TCD flow velocities, often into the normal range. A multicenter trial is warranted to determine the efficacy of hydroxyurea for the management of increased TCD values, and ultimately for primary stroke prevention in children with SCA.

Description: Key Points Children with SCA and stroke show severe parenchymal and vascular abnormalities that can be assessed using a vasculopathy grading scale. Results from the SWiTCH Trial support concerns about ineffectiveness of transfusion therapy in preventing cerebrovascular injury progression.

Description: Hydroxyurea improves hematologic parameters for children with sickle cell disease (SCD), but its long-term efficacy at maximum tolerated dose (MTD) has not been determined. Between 1995 and 2002, hydroxyurea therapy was initiated for 122 pediatric patients with SCD including 106 with homozygous sickle cell anemia (HbSS), 7 with sickle hemoglobin C (HbSC), 7 with sickle/β-thalassemia (HbS/ β-thalassemia [6 HbS/β0, 1 HbS/β+]), and 2 with sickle hemoglobin OArab (HbS/OArab). Median age at initiation of therapy was 11.1 years. Hydroxyurea was escalated to MTD, with an average dose of 25.4 ± 5.4 mg/kg per day; the average duration of hydroxyurea therapy has been 45 ± 24 months (range, 6-101 months). Hydroxyurea was discontinued for 15 (12%) children with poor compliance. Mild transient neutropenia occurred, but no hepatic or renal toxicity was noted. Hydroxyurea therapy led to significant increases in hemoglobin level, mean corpuscular volume, and fetal hemoglobin (HbF) level, whereas significant decreases occurred in reticulocyte, white blood cell, and platelet counts and serum bilirubin levels. Children with variant SCD genotypes also had hematologic responses to hydroxyurea. HbF induction has been sustained for up to 8 years without adverse effects on growth or increased numbers of acquired DNA mutations. Long-term hydroxyurea therapy at MTD is well tolerated by pediatric patients with SCD and has sustained hematologic efficacy with apparent long-term safety.

Description: Stroke is a devastating complication of sickle cell anemia (SCA), affecting 5% to 10% of patients before adulthood. Several candidate genetic polymorphisms have been proposed to affect stroke risk, but few have been validated, mainly because previous studies were hampered by relatively small sample sizes and the absence of additional patient cohorts for validation testing. To verify the accuracy of proposed genetic modifiers influencing stroke risk in SCA, we performed genotyping for 38 published single nucleotide polymorphisms (SNPs), as well as α-thalassemia, G6PD A− variant deficiency, and β-globin haplotype in 2 cohorts of children with well-defined stroke phenotypes (130 stroke, 103 nonstroke). Five polymorphisms had significant influence (P 〈 .05): SNPs in the ANXA2, TGFBR3, and TEK genes were associated with increased stroke risk, whereas α-thalassemia and a SNP in the ADCY9 gene were linked with decreased stroke risk. Further investigation at these genetic regions may help define mutations that confer stroke risk or protection in children with SCA.

Description: Children with sickle cell disease (SCD) and stroke receive chronic transfusions to prevent stroke recurrence. Transfusion risks including infection, erythrocyte allosensitization, and iron overload suggest a need for alternative therapies. We previously used hydroxyurea (HU) and phlebotomy in two young adults with SCD and stroke as an alternative to transfusions. We have now prospectively discontinued transfusions in 16 pediatric patients with SCD and stroke. Reasons to discontinue transfusions included erythrocyte alloantibodies or autoantibodies, recurrent stroke on transfusions, iron overload, noncompliance, and deferoxamine allergy. HU was started at 15 mg/kg/d and escalated to 30 mg/kg/d based on hematologic toxicity. Patients with iron overload underwent phlebotomy. The children have been off transfusions 22 months, (range, 3 to 52 months). Their average HU dose is 24.9 ± 4.2 mg/kg/d, hemoglobin concentration is 9.4 ± 1.3 g/dL, and mean corpuscular volume (MCV) is 112 ± 9 fL. Maximum percentage fetal hemoglobin (%HbF) is 20.6% ± 8.0% and percentage HbF-containing erythrocytes (%F cells) is 79.3% ± 14.7%. Fourteen patients underwent phlebotomy with an average of 8,993 mL (267 mL/kg) removed. Serum ferritin has decreased from 2,630 to 424 ng/mL, and 4 children have normal ferritin values. Three patients (19%) had neurological events considered recurrent stroke, each 3 to 4 months after discontinuing transfusions, but before maximal HU effects. These preliminary data suggest some children with SCD and stroke may discontinue chronic transfusions and use HU therapy to prevent stroke recurrence. Phlebotomy is well-tolerated and significantly reduces iron overload. Modifications in HU therapy to raise HbF more rapidly might increase protection against stroke recurrence.

Description: Children with sickle cell anemia have a 5–10% incidence of primary stroke, after which they have a 50–90% risk of stroke recurrence. Monthly transfusions with a goal of maintaining sickle hemoglobin (HbS) 7 days after the scheduled date) occurring once in 22% and twice or more in 12% of children. The average pre-transfusion Hb was 9.0 ± 0.7 gm/dL. The average pre-transfusion %HbS was 35 ± 11 %, with a median %HbS value of 34%. Potential "cutoff " %HbS values for SWiTCH included 34% (50th percentile of reported values), 43% (75th percentile), and 52% HbS (90th percentile). These data indicate that transfusions to prevent recurrent stroke vary among academic pediatric institutions and 30% HbS may not be a realistic goal for this study. Although the goal for transfusions in the SWiTCH standard treatment arm will remain 30% HbS, maintaining an average pre-transfusion HbS value of ≤ 45% will be required to reflect the academic community standard.