Is blood pressure reduction a valid surrogate endpoint for stroke prevention? an analysis incorporating a systematic review of randomised controlled trials, a by-trial weighted errors-in-variables regression, the surrogate threshold effect (STE) and the biomarker-surrogacy (BioSurrogate) evaluation schema (BSES)

<p>Abstract</p> <p>Background</p> <p>Blood pressure is considered to be a leading example of a valid surrogate endpoint. The aims of this study were to (i) formally evaluate systolic and diastolic blood pressure reduction as a surrogate endpoint for stroke prevention and (ii) determine what blood pressure reduction would predict a stroke benefit.</p> <p>Methods</p> <p>We identified randomised trials of at least six months duration comparing any pharmacologic anti-hypertensive treatment to placebo or no treatment, and reporting baseline blood pressure, on-trial blood pressure, and fatal and non-fatal stroke. Trials with fewer than five strokes in at least one arm were excluded. Errors-in-variables weighted least squares regression modelled the reduction in stroke as a function of systolic blood pressure reduction and diastolic blood pressure reduction respectively. The lower 95% prediction band was used to determine the minimum systolic blood pressure and diastolic blood pressure difference, the surrogate threshold effect (STE), below which there would be no predicted stroke benefit. The STE was used to generate the surrogate threshold effect proportion (STEP), a surrogacy metric, which with the R-squared trial-level association was used to evaluate blood pressure as a surrogate endpoint for stroke using the Biomarker-Surrogacy Evaluation Schema (BSES3).</p> <p>Results</p> <p>In 18 qualifying trials representing all pharmacologic drug classes of antihypertensives, assuming a reliability coefficient of 0.9, the surrogate threshold effect for a stroke benefit was 7.1 mmHg for systolic blood pressure and 2.4 mmHg for diastolic blood pressure. The trial-level association was 0.41 and 0.64 and the STEP was 66% and 78% for systolic and diastolic blood pressure respectively. The STE and STEP were more robust to measurement error in the independent variable than R-squared trial-level associations. Using the BSES3, assuming a reliability coefficient of 0.9, systolic blood pressure was a B + grade and diastolic blood pressure was an A grade surrogate endpoint for stroke prevention. In comparison, using the same stroke data sets, no STEs could be estimated for cardiovascular (CV) mortality or all-cause mortality reduction, although the STE for CV mortality approached 25 mmHg for systolic blood pressure.</p> <p>Conclusions</p> <p>In this report we provide the first surrogate threshold effect (STE) values for systolic and diastolic blood pressure. We suggest the STEs have face and content validity, evidenced by the inclusivity of trial populations, subject populations and pharmacologic intervention populations in their calculation. We propose that the STE and STEP metrics offer another method of evaluating the evidence supporting surrogate endpoints. We demonstrate how surrogacy evaluations are strengthened if formally evaluated within specific-context evaluation frameworks using the Biomarker- Surrogate Evaluation Schema (BSES3), and we discuss the implications of our evaluation of blood pressure on other biomarkers and patient-reported instruments in relation to surrogacy metrics and trial design.</p

Rituximab for induction and maintenance treatment of ANCA-associated vasculitides: a multicentre retrospective study on 80 patients

International audienceOBJECTIVES: Rituximab has been shown to induce remission of ANCA-associated vasculitides (AAVs). Our study was undertaken to describe AAV clinical responses to rituximab used for remission-induction and/or maintenance therapy, assess rituximab's safety profile and evaluate French clinical practices. METHODS: This retrospective study concerned AAV patients who had received one or more rituximab infusion between 2002 and January 2011 and had follow-up lasting ≥12 months. RESULTS: Eighty patients were included, most with refractory or relapsing AAV: 70 (88%) with granulomatosis with polyangiitis (GPA), 9 (11%) with microscopic polyangiitis and 1 (1%) with eosinophilic GPA. Rituximab was the first agent used to induce remission in 73 patients. The two most commonly administered regimens were an infusion of 375 mg/m(2)/week for 4 weeks (54 patients) and an infusion of 1 g every 2 weeks for a month (16 patients). Rituximab was first prescribed to maintain remission in seven patients. Respective 1-, 2-, and 3-year relapse-free survival rates after the first infusion were 80% (95% CI 72, 89), 63% (51, 77) and 52% (39, 70). Relapse-free survival was longer for patients receiving rituximab maintenance therapy (P = 0.002). Among 22 (28%) rituximab-treated patients experiencing severe adverse events, 12 (15%) had infectious complications leading to 4 (5%) deaths. Only 15 (19%) patients had received anti-pneumococcal vaccine before rituximab. CONCLUSION: Rituximab was able to induce AAV remission and seemed to maintain remission better than other agents, but caution is needed concerning its safety, especially regarding bacterial infections, in this population