Challenge and Yield of Enrolling Racially and Ethnically Diverse Patient Populations in Low Event Rate Clinical Trials.

BACKGROUND AND PURPOSE: We report patient enrollment and retention by race and ethnicity in the CREST (Carotid Revascularization Endarterectomy Versus Stent Trial) and assess potential effect modification by race/ethnicity. In addition, we discuss the challenge of detecting differences in study outcomes when subgroups are small and the event rate is low. METHODS: We compared 2502 patients by race, ethnicity, baseline characteristics, and primary outcome (any periprocedural stroke, death, or myocardial infarction and subsequent ipsilateral stroke up to 10 years). RESULTS: Two hundred forty (9.7%) patients were minority by race (6.1%) or ethnicity (3.6%); 109 patients (4.4%) were black, 32 (1.3%) Asian, 2332 (93.4%) white, 11 (0.4%) other, and 18 (0.7%) unknown. Ninety (3.6%) were Hispanic, 2377 (95%) non-Hispanic, and 35 (1.4%) unknown. The rate of the primary end point for all patients was 10.9%±0.9% at 10 years and did not differ by race or ethnicity (Pinter>0.24). CONCLUSIONS: The proportion of minorities recruited to CREST was below their representation in the general population, and retention of minority patients was lower than for whites. Primary outcomes did not differ by race or ethnicity. However, in CREST (like other studies), the lack of evidence of a racial/ethnic difference in the treatment effect should be interpreted with caution because of low statistical power to detect such a difference. CLINICAL TRIAL REGISTRATION: URL: http://www.clinicaltrials.gov. Unique identifier: NCT00004732.

Factors Associated With Time to Site Activation, Randomization, and Enrollment Performance in a Stroke Prevention Trial.

BACKGROUND AND PURPOSE: Multicenter clinical trials attempt to select sites that can move rapidly to randomization and enroll sufficient numbers of patients. However, there are few assessments of the success of site selection. METHODS: In the CREST-2 (Carotid Revascularization and Medical Management for Asymptomatic Carotid Stenosis Trials), we assess factors associated with the time between site selection and authorization to randomize, the time between authorization to randomize and the first randomization, and the average number of randomizations per site per month. Potential factors included characteristics of the site, specialty of the principal investigator, and site type. RESULTS: For 147 sites, the median time between site selection to authorization to randomize was 9.9 months (interquartile range, 7.7, 12.4), and factors associated with early site activation were not identified. The median time between authorization to randomize and a randomization was 4.6 months (interquartile range, 2.6, 10.5). Sites with authorization to randomize in only the carotid endarterectomy study were slower to randomize, and other factors examined were not significantly associated with time-to-randomization. The recruitment rate was 0.26 (95% confidence interval, 0.23-0.28) patients per site per month. By univariate analysis, factors associated with faster recruitment were authorization to randomize in both trials, principal investigator specialties of interventional radiology and cardiology, pre-trial reported performance >50 carotid angioplasty and stenting procedures per year, status in the top half of recruitment in the CREST trial, and classification as a private health facility. Participation in StrokeNet was associated with slower recruitment as compared with the non-StrokeNet sites. CONCLUSIONS: Overall, selection of sites with high enrollment rates will likely require customization to align the sites selected to the factor under study in the trial. CLINICAL TRIAL REGISTRATION: URL: http://www.clinicaltrials.gov. Unique identifier: NCT02089217.

Mediators of the Age Effect in the Carotid Revascularization Endarterectomy Versus Stenting Trial (CREST).

BACKGROUND AND PURPOSE: There is higher combined risk of stroke or death (S+D) at older ages with carotid stenting. We assess whether this can be attributed to patient or arterial characteristics that are in the pathway between older age and higher risk. METHODS: Mediation analysis of selected patient (hypertension, diabetes mellitus, and dyslipidemia) and arterial characteristics assessed at the clinical sites and the core laboratory (plaque length, eccentric plaque, ulcerated plaque, percent stenosis, peak systolic velocity, and location) was performed in 1123 carotid artery stenting-treated patients in the Carotid Revascularization Endarterectomy Versus Stenting Trial (CREST). We assessed the association of age with these characteristics, the association of these characteristics with stroke risk, and the amount of mediation of the association of age on the combined risk of periprocedural S+D with adjustment for these factors. RESULTS: Only plaque length as measured at the sites increased with age, was associated with increased S+D risk and significantly mediated the association of age on S+D risk. However, adjustment for plaque length attenuated the increased risk per 10 years of age from 1.72 (95% confidence interval, 1.26-2.37) to 1.66 (95% confidence interval, 1.20-2.29), accounting for only 8% of the increased risk. CONCLUSIONS: Plaque length seems to be in the pathway between older age and higher risk of S+D among carotid artery stenting-treated patients, but it mediated only 8% of the age effect excess risk of carotid artery stenting in CREST. Other factors and mechanisms underlying the age effect need to be identified as plaque length will not identify elderly patients for whom stenting is safe relative to endarterectomy. CLINICAL TRIAL REGISTRATION: URL: http://www.clinicaltrials.gov. Unique identifier: NCT00004732.

Characteristics of participants consenting versus declining follow-up for up to 10 years in a randomized clinical trial.

BACKGROUND: With patients living a decade or longer post-procedure, long-term data are needed to assess the durability of carotid artery stenting versus carotid endarterectomy. Identifying characteristics of those consenting or declining to continue in long-term follow-up may suggest strategies to improve retention in clinical trials. PURPOSE: This report describes differences between patients choosing or declining to continue follow-up for up to 10 years in the Carotid Revascularization Endarterectomy versus Stenting Trial. METHODS: Following completion of the primary outcome, patients who were in active Carotid Revascularization Endarterectomy versus Stenting Trial follow-up were asked to continue beyond their original 4-year commitment for a maximum of 10 years. The characteristics of those who consented were compared with those who declined. Univariate and multivariable logistic regression were used for analysis, and backwards stepwise logistic regression (the most parsimonious model) was used to determine the factors associated with continuation. RESULTS: Of the 1921 active Carotid Revascularization Endarterectomy versus Stenting Trial participants for whom consent to extend follow-up was requested, 1695 (88%; mean age: 68.4) consented; 226 (12%; mean age: 69.6) declined. Of those who did not consent versus those who consented, 66% versus 48% were symptomatic at baseline (p<0.0001), at follow-up 28% versus 20% were smokers (p=0.009), 85% versus 90% were hypertensive (p=0.01), and 84% versus 94% were dyslipidemic (p<0.0001). Additional factors that differed between those who did not consent and those who consented included the mean number of years in the study at time of consent (4.8 years vs 3.7 years (p=<0.0001)) and patients from sites that enrolled <30 patients compared to sites randomizing 30 or more (70% vs 52% (p<0.0001)). Multivariable logistic regression indicated that those with lesser odds of consenting to the extended follow-up were older (odds ratio: 0.80; 95% confidence interval: 0.67, 0.96), more likely to be symptomatic (odds ratio: 0.58; 95% confidence interval: 0.42, 0.80), smokers (odds ratio: 0.48; 95% confidence interval: 0.34, 0.70), were in the study 5+ years versus <3 (odds ratio: 0.21; 95% confidence interval: 0.13, 0.34), and at a site that randomized <30 patients (odds ratio: 0.46; 95% confidence interval: 0.33, 0.63), while patients with dyslipidemia at follow-up had increased odds of consenting (odds ratio: 2.28 (1.47, 3.54)). CONCLUSION: Symptomatic status, increasing age, randomized at lower volume centers, and longer time in follow-up were associated with reduced odds of consenting to long-term follow-up. Identifying factors associated with reduced willingness to extend participation long-term can suggest targeted strategies to improve retention in future clinical trials.

Management of vascular risk factors in the Carotid Revascularization Endarterectomy Versus Stenting Trial (CREST).

BACKGROUND: The Carotid Revascularization Endarterectomy Versus Stenting Trial (CREST) is a multicenter randomized trial of stenting versus endarterectomy in patients with symptomatic and asymptomatic carotid disease. This study assesses management of vascular risk factors. METHODS AND RESULTS: Management was provided by the patient's physician, with biannual monitoring results collected by the local site. Therapeutic targets were low-density lipoprotein, cholesterol <100 mg/dL, systolic blood pressure <140 mm Hg, fasting blood glucose <126 mg/dL, and nonsmoking status. Optimal control was defined as achieving all 4 goals concurrently. Generalized estimating equations were used to compare risk factors at baseline with those observed in scheduled follow-up visits for up to 48 months. In the analysis cohort of 2210, significant improvements in risk-factor control were observed across risk factors for all follow-up visits compared with baseline. At 48 months, achievement of the low-density lipoprotein cholesterol goal improved from 59.1% to 73.6% (P<0.001), achievement of the systolic blood pressure goal improved from 51.6% to 65.1% (P<0.001), achievement of the glucose goal improved from 74.9% to 80.7% (P=0.0101), and nonsmoking improved from 74.4% to 80.9% (P<0.0001). The percentage with optimal risk-factor control also improved significantly, from 16.7% to 36.2% (P<0.001), but nearly 2 of 3 study participants did not achieve optimal control during the study. CONCLUSIONS: Site-based risk-factor control improved significantly in the first 6 months and over the long term in CREST but was often suboptimal. Intensive medical management should be considered for future trials of carotid revascularization. CLINICAL TRIAL REGISTRATION URL: ClinicalTrials.gov. Unique identifier: NCT00004732.

Financial management of a large multisite randomized clinical trial.

BACKGROUND: The Carotid Revascularization Endarterectomy versus Stenting Trial (CREST) received five years' funding ($21 112 866) from the National Institutes of Health to compare carotid stenting to surgery for stroke prevention in 2500 randomized participants at 40 sites. AIMS: Herein we evaluate the change in the CREST budget from a fixed to variable-cost model and recommend strategies for the financial management of large-scale clinical trials. METHODS: Projections of the original grant's fixed-cost model were compared to the actual costs of the revised variable-cost model. The original grant's fixed-cost budget included salaries, fringe benefits, and other direct and indirect costs. For the variable-cost model, the costs were actual payments to the clinical sites and core centers based upon actual trial enrollment. We compared annual direct and indirect costs and per-patient cost for both the fixed and variable models. Differences between clinical site and core center expenditures were also calculated. RESULTS: Using a variable-cost budget for clinical sites, funding was extended by no-cost extension from five to eight years. Randomizing sites tripled from 34 to 109. Of the 2500 targeted sample size, 138 (5·5%) were randomized during the first five years and 1387 (55·5%) during the no-cost extension. The actual per-patient costs of the variable model were 9% ($13 845) of the projected per-patient costs ($152 992) of the fixed model. CONCLUSIONS: Performance-based budgets conserve funding, promote compliance, and allow for additional sites at modest additional cost. Costs of large-scale clinical trials can thus be reduced through effective management without compromising scientific integrity.

Stroke after carotid stenting and endarterectomy in the Carotid Revascularization Endarterectomy versus Stenting Trial (CREST).

BACKGROUND: Stroke occurs more commonly after carotid artery stenting than after carotid endarterectomy. Details regarding stroke type, severity, and characteristics have not been reported previously. We describe the strokes that have occurred in the Carotid Revascularization Endarterectomy versus Stenting Trial (CREST). METHODS AND RESULTS: CREST is a randomized, open-allocation, controlled trial with blinded end-point adjudication. Stroke was a component of the primary composite outcome. Patients who received their assigned treatment within 30 days of randomization were included. Stroke was adjudicated by a panel of board-certified vascular neurologists with secondary central review of clinically obtained brain images. Stroke type, laterality, timing, and outcome were reported. A periprocedural stroke occurred among 81 of the 2502 patients randomized and among 69 of the 2272 in the present analysis. Strokes were predominantly minor (81%, n=56), ischemic (90%, n=62), in the anterior circulation (94%, n=65), and ipsilateral to the treated artery (88%, n=61). There were 7 hemorrhages, which occurred 3 to 21 days after the procedure, and 5 were fatal. Major stroke occurred in 13 (0.6%) of the 2272 patients. The estimated 4-year mortality after stroke was 21.1% compared with 11.6% for those without stroke. The adjusted risk of death at 4 years was higher after periprocedural stroke (hazard ratio, 2.78; 95% confidence interval, 1.63-4.76). CONCLUSIONS: Stroke, particularly severe stroke, was uncommon after carotid intervention in CREST, but stroke was associated with significant morbidity and was independently associated with a nearly 3-fold increased future mortality. The delayed timing of major and hemorrhagic stroke after revascularization suggests that these strokes may be preventable.

Interventions to increase enrollment in a large multicenter phase 3 trial of carotid stenting vs. endarterectomy.

BACKGROUND: Randomized clinical trials often encounter slow enrollment. Failing to meet sample size requirements has scientific, financial, and ethical implications. AIMS: We report interventions used to accelerate recruitment in a large multicenter clinical trial that was not meeting prespecified enrollment commitments. METHODS: The Carotid Revascularization Endarterectomy vs. Stenting Trial began randomization in December 2000. To accelerate enrollment, multiple recruitment tactics were initiated, which included expanding the number of sites, hiring a recruitment director (May 2003), broadening eligibility criteria (April 2005), branding with a study logo, Web site, and recruitment materials, increasing site visits by study leadership, sending e-mails to the site teams after every enrollment, distributing electronic newsletters, and implementing investigator and coordinator conferences. RESULTS: From December 2000 through May 2003, 14 sites became active (54 patients randomized), from June 2003 through April 2005, 44 sites were added (404 patients randomized), and from May 2005 through July 2008, 54 sites were added (2044 patients randomized). During these time intervals, the number of patients enrolled per site per year was 1·5, 3·6, and 5·6. For the single years 2004 to 2008, the mean monthly randomization rates per year were 19·7, 38·1, 56·4, 53·0, and 54·7 (annualized), respectively. Enrollment was highest after recruitment tactics were implemented: 677 patients in 2006, 636 in 2007, and 657 in 2008 (annualized). The prespecified sample size of 2502 patients, 47% asymptomatic, was accomplished on July 2008. CONCLUSIONS: Aggressive recruitment tactics and investment in a full-time recruitment director who can lead implementation may be effective in accelerating recruitment in multicenter trials.

Does sex matter? Thirty-day stroke and death rates after carotid artery stenting in women versus men: results from the Carotid Revascularization Endarterectomy versus Stenting Trial (CREST) lead-in phase.

BACKGROUND AND PURPOSE: Several carotid endarterectomy randomized, controlled trials and series have reported higher perioperative stroke and death rates for women compared with men. The potential for this same relationship with carotid artery stenting was examined in the lead-in phase of the Carotid Revascularization Endarterectomy versus Stenting Trial (CREST). METHODS: CREST compares efficacy of carotid endarterectomy and carotid artery stenting in preventing stroke, myocardial infarction, and death in the periprocedural period and ipsilateral stroke over the follow-up period. CREST included a "lead-in" phase of symptomatic (>or=50% stenosis) and asymptomatic (>or=70% stenosis) patients. Patients were examined by a neurologist preprocedure, at 24 hours, and at 30 days. Review of stroke and death was by an independent events committee. The association of sex with periprocedural stroke and death was examined in 1564 patients undergoing carotid artery stenting (26.5% symptomatic). RESULTS: Women comprised 37% of the lead-in cohort and did not differ from men by age, symptomatic status, or characteristics of the internal carotid artery. The 30-day stroke and death rate for women was 4.5% (26 of 579; 95% CI, 3.0% to 6.5%) compared with 4.2% (41 of 985; 95% CI, 3.0% to 5.6%) for men. The difference in stroke and death rate was not significant nor were there any significant differences by sex after adjustment for age, arterial characteristics, or cardiovascular risk factors. CONCLUSIONS: These results do not provide evidence that women have a higher carotid artery stenting stroke and death rate compared with men. The potential differential periprocedural risk by sex will be prospectively addressed in the randomized phase of CREST.