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Rationale: Why do we still need a large trial? IST-3 The Third International Stroke Trial: National Coordinators’ Meet

Rationale: Why do we still need a large trial? IST-3 The Third International Stroke Trial: National Coordinators’ Meeting 25 May 2005, Bologna. Professor Richard Lindley, Co-Principal Investigator. Outline. Why large trials? Why do we need more randomised evidence? Small evidence base

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Rationale: Why do we still need a large trial? IST-3 The Third International Stroke Trial: National Coordinators’ Meet

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  1. Rationale: Why do we still need a large trial? IST-3 The Third International Stroke Trial: National Coordinators’ Meeting25 May 2005, Bologna Professor Richard Lindley, Co-Principal Investigator

  2. Outline • Why large trials? • Why do we need more randomised evidence? • Small evidence base • Variation in clinical practice • Areas of uncertainty • Current trials • IST3 design

  3. Rationale for large trials • Acute ischaemic stroke treatment currently unsatisfactory • Aspirin effective but has only modest benefit (approximately 1% absolute benefit) BUT currently has a greater public health impact than thrombolysis (large number of patients treated with a modestly effective treatment) • Thrombolysis proven to be effective for only highly selected patients (10-15% absolute benefit) BUT few treated and minimal public health benefit (small number of patients treated with a powerful treatment)

  4. History of acute stroke trials • Modern era dependent on wide-spread availability of CT (and MRI) scanners, therefore a short history • Only two “mega-trials” IST and CAST • Industry dominated acute stroke trials all seriously underpowered (in comparison to secondary prevention stroke trials)

  5. Lubeluzole • N = 3510 patients, confidence interval for death or dependency at the end of follow-up 0.91 to 1.19 • Trials only powered to detect a 10-15% absolute benefit

  6. Gavestinel (GAIN trials) • GAIN Americas, 90% power to detect a 10% absolute benefit (n = 1646), 2% absolute benefit observed for independent survival BUT 4% more dead • GAIN International, 90% power to detect a 6-10% absolute benefit (n=1800), - 0.8% absolute benefit observed for independent survival and 1.6% more dead (95% CI for odds ratio for worse outcome 0.81 to 1.26)

  7. Trials in acute stroke are far too small “It is still not sufficiently widely appreciated just how large clinical trials need to be to detect reliably the sort of moderate, but important, differences in major outcomes that might exist (especially if effects in different subgroups are to be assessed reliably).” Collins and MacMahon Lancet 2001; 357: 373-380

  8. Neuroprotectors unlikely to have a major treatment benefit You need to OPEN occluded arteries

  9. With trials of about 20,000 subjects, the pharmaceutical industry can be reassured that they have not missed an important new treatment for acute stroke

  10. Worthwhile reductions in stroke death and disability 60% dead or disabled at six months in control group 58% dead or disabled at six months in treatment group Sample sizePower 5000 50% 9000 80% 13000 90% 16000 95%

  11. Lessons from cardiology ISIS-2 Mortality in placebo group 13% TrialMortality in best treatment arm ISIS-2 8% ISIS-4 7% GUSTO 6% Message: Moderate cumulative treatment effects halved MI mortality over a 10 year period

  12. Lessons from stroke medicine IST Death/dependency in control group 64% TrialDeath/dependency in besttreatment arm IST 63% (aspirin) Stroke units 58% rt-PA 58% (i.e. current negligible impact) Message: Moderate cumulative treatment effects have potential impact in stroke

  13. Lessons from cardiology ISIS-1 1986 16,000 patients ISIS-2 1988 17,000 patients ISIS-3 1992 40,000 patients GUSTO 1993 41,000 patients ISIS-4 1995 60,000 patients

  14. Thrombolytic Time Window: Acute MI 60,000 patients from “mega-trials” Fibrinolytic Therapy Trialists’ Group. Lancet 1994;343:311-322

  15. Thrombolysis for acute ischaemic stroke • Standard accepted treatment for MI • Slow acceptance for acute stroke

  16. 624 patients Clinical inclusion criteria CT scan to exclude a bleed or mimic (no other exclusions) Treatment to begin within 3 hours of stroke i.v. rt-PA 0.9mg/kg over 1 hour Major treatment effect 120-160 more independent survivors per 1,000 treatment Independent re-analysis 2003 confirms results 10 years later treatment not widely implemented NINDS Trial Published in 1995

  17. 800 patients 18 to 80 years Clinical inclusion criteria CT scan to exclude a bleed, mimic and > 1/3 MCA ischaemia) Treatment to begin within 6 hours of stroke i.v. rt-PA 0.9mg/kg over 1 hour Non-significant modest benefit 37 more independent survivors per 1,000 treatment 7 years later treatment not implemented for 3-6 hour time window ECASS II Published in 1998

  18. Powered to detect a 10% absolute difference with 80% power Detected a 3.7% absolute difference ECASS II Published in 1998

  19. Aged 18 to 80 years 800 patients recruited 3-4 hours post stroke Still powered to detect a 10% absolute difference, this time with 90% power ECASS III Currently recruiting

  20. Evidence

  21. Randomised trials of thrombolysis vs control in acute myocardial infarction Total no. patients 1994 58,600 Randomised trials trials of thrombolysis vs control in acute ischaemic stroke Total (all agents) 2005 5,675 rt-PA 2005 2,700 rt-PA < 3hrs 2005 930 rt-PA aged > 80 years 42

  22. i.v. rt-PA benefit <6 hours: reduction in ‘death or dependency’ 20% reduction with rt-PA (95% CI 7-23%) BUT thesignificant between- trial heterogeneity (I2=62%) makes result unreliable

  23. Unacceptable variation in usage in clinical practice

  24. Only a small, variable proportion of patients get rt-PA in USA, Germany Author no. no. % treated hospitals patients rt-PA (range) USA Johnstone 42 1,195 4.1% (0-12%) Furlan 29 3,948 1.8% (0-10%) Reed 137 23,058 1.6% (0-5%) Germany Heuschmann 104 13,440 3.0% (0-18%)

  25. Effect of hospital, age and presence of neurologist on likelihood of receiving thrombolysis for acute ischaemic stroke among 23,058 acute stroke patients from 137 community hospitals in USA • In 35% of hospitals, no patients at all given rt-PA. • Strong trends to less rt-PA use: • with increasing age, • if no neurologist available Reed et al. Stroke 2001: 32; 1832-44

  26. Variation in use of rt-PA for acute ischaemic stroke ‘within licence’ in Europe SITS register (2003-5) March 2005

  27. ‘Grey areas’ of uncertainty: i.v. rt-PA promising but unproven for patients who: • Present < 3hrs & do not exactly meet NINDS criteria • All patients 3-6hours • Older patients (>75 years) • Severe stroke, mild stroke…... • Have subtle, early ischaemic change on CT • Etc etc …

  28. Sample size required to answer these questions about iv rt-PA reliably 0-1.5 1.5-3.0 3.0-4.5 4.5-6.0 hours rt-PA study group. Lancet 2004; 363: 768–74

  29. Current trials

  30. Current randomised trials of i.v. thrombolysis

  31. IA thrombolysis MELT SYNTHESIS GP IIb/IIIA AbESTT2 (n=1800) CLEAR ROSIE SETIS SATIS Mechanical MR-RESCUE Ultrasound +/- rt-PA CLOTBUST-2? MUST Small (n< 300) trials of other interventions

  32. None of these trials will reliably answer the main questions

  33. Main features of IST - 3 • International, multi-centre, Prospective, Randomised, Open, Blinded Endpoints study of i.v. rt-PA vs control. • Target 6000 patients • Primary outcome: the proportion of patients alive and independent at six months (Modified Rankin 0,1 or 2) • Central telephone randomisation with on-line minimisation to balance key prognostic factors. • Web-based blinded detailed central review of all scans (ASPECTS, 1/3 MCA rule, dense MCA etc) • Conducted to EU GCP standards. IST - 3 Protocol

  34. IST-3 Sample size: 6,000 patients • 1500 patients randomised within 3 hours will give >95% power (alpha 0.05) to detect a 10% increase in the proportion of patients alive and independent at 6 months (40% to 50%). • 4500 patients randomised from 3 to 6 hours will give >90% power (alpha 0.05) to detect a 5% increase in the proportion of patients alive and independent at 6 months (40% to 45%). IST - 3 Protocol

  35. IST-3 main eligibility criteria • Symptoms and signs of clinically definite acute stroke • Time of onset of stroke is known and treatment can be started within 6 hours of this onset • CT or MRI has reliably excluded both intracranial haemorrhage and structural brain lesions which can mimic stroke • Fuller details at: www.ist3.com

  36. IST-3 main exclusion criteria • Major surgery, trauma,GI or urinary tract haemorrhage within previous 21 days • Arterial puncture at a non-compressible site within the previous 7 days • Any known coagulation defect • Hypo- or hyperglycaemia sufficient to account for neurological symptoms

  37. Early infarct signs on CT Hypodensity : loss of grey/white differentiation, loss of the lentiform nucleus Swelling : effacement of sulci, squashing the ventricle 4 hours 24 hours

  38. IST-3: Training to read CT scans • web-based CT reading and feedback system: • Log on to www.neuroimage.co.uk • Register • Do first 20 scans (2 batches) • - get 1 CPD credit • get feedback • Do all six batches • - get 5 CPD credits what you, the reference standard, five experts and all other specialties said about that scan, and a follow-up scan to see where the infarct appeared

  39. IST-3 Imaging:Training materials to read scans

  40. IST-3 Imaging:Training materials to read scans

  41. IST-3 trial: randomisation If patient fits main eligibility/exclusion criteria, Clinician/patient/family discuss. If: • Clear INDICATION FOR rt-PA TREAT (i.e. meets terms of current licence and patient agrees) • Clear CONTRAINDICATION TO rt-PA  DON’T TREAT • rt-PA ‘PROMISING BUT UNPROVEN’ RANDOMISE

  42. Conclusion. Need to • Implement existing knowledge: redesign services to increase equity of access to thrombolysis within licence • Increase the evidence base; worldwide effort to randomise sufficient patients to in IST-3 (and other trials) to provide reliable evidence on current questions • Be aware of benefits of participating in IST-3: • It helps address a ‘real world’ intervention • You will get education on acute stroke care/CT scanning • If the trial result is positive, active trial centres more likely to be able to adopt new treatment quickly

  43. New UK centres needed: please encourage other centres to join the trial register at www.ist3.com

  44. Can we get 10-20% of ischaemic stroke treated with rt-PA? 999 Within 6 Hrs Nurse led Stroke Management process - Evaluation and Triage

  45. To achieve this we need seriously reliable data on: • Treatment effect to 6 hours (and maybe beyond) • Treatment effects by age, stroke subtype, severity, presence of aspirin and early ischaemic change on CT etc

  46. Such change requires a convincing trial! Impact of megatrials in cardiology on thrombolysis for MI

  47. IST-3: The window of opportunity • In 1998 acute stroke services were too under-developed for a thrombolysis “mega-trial” • Stroke services world-wide are being developed and maturing • rt-PA has a track record in an “effective but not useful” time window • It is now the most promising treatment to evaluate

  48. IST-3: Streamlined design • Methodology of large simple stroke trial developed over 15 years • IST-3 designed with consumers and collaborative group • Central organisation and delegated responsibilities share as much of the work as possible • Evidence based trial monitoring!

  49. AbESTT-2 IST-3 IST-3 is simple & streamlined! Compare the paperwork needed for AbESTT-2 trial vs IST-3

  50. So we need hospital teams to be treating stroke as an emergency… …and not lounging around drinking coffee!

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