The Virtual International Stroke Trials Archive (VISTA): promulgation of a clinial trial resource

Ali, Myzoon (2008) The Virtual International Stroke Trials Archive (VISTA): promulgation of a clinial trial resource. PhD thesis, University of Glasgow.

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Abstract

Abstract
Chapter 1 provides an introduction to stroke including its current prevalence both
nationally and globally, aetiology, global importance and social & financial burden. We
also describe here current acute stroke management practices, the role of clinical trials
in the development of therapies, the richness of data within clinical trials and changes
in regulatory thinking regarding data access. We provide recommendations for the use
of trial data for novel exploratory investigations of clinical trial design and
epidemiological studies.
In Chapter 2 we describe the establishment of the Virtual International Stroke Trials
Archive (VISTA) to address the need for reliable data on which to plan future clinical
trials. This chapter details the methodology and logistics of establishing the resource,
including details of regulatory policy for data collection and use, establishment of a
Steering Committee and development of a constitution to safeguard data access and
use.
As of June 2008, VISTA contains 28 acute stroke clinical trials and one acute stroke
registry. We collated data on over 27,500 patients with either ischaemic or
haemorrhagic stroke. Patient age ranges from 18 to 103 years and outcome measures
include Barthel Index, Scandinavian Stroke Scale, National Institutes of Health Stroke
Scale, Orgogozo Scale, and modified Rankin Scale. Medical history and onset to
treatment times are readily available and computed tomography (CT) lesion data are
available for selected trials. We discuss the establishment and potential uses of this
resource in the context of existing stroke resources.
Chapter 3 demonstrates how we utilised VISTA to investigate natural history patterns in
acute stroke. There are prominent differences in stroke incidence and outcome across
different geographical locations; these are not confined to the Eastern- Western axis.
We aimed to examine whether there were any differences in index stroke severity,
stroke risk factors, and stroke outcome between geographical locations, after adjusting
for case-mix.
We found that patients who were enrolled in the USA and Canada had the worst index
strokes, whilst patients enrolled in Austria and Switzerland had the mildest index
stroke, and better functional (p=0.023) and neurological outcome (p=0.034) at 90 days.
90 –day survival was greater in patients who were enrolled in Spain and Portugal
(p<0.0001).
Chapter 4 demonstrates the use of VISTA to inform stroke clinical trial design by
examining the impact of early follow up on adverse event and functional outcome
profiles. We aimed to assess the contribution of adverse complications unrelated to
stroke, to 30 and 90- day functional outcome. If fewer ‘stroke-unrelated’ adverse
events were seen at later time points, and if the absence of these events appeared to
influence functional outcome, then further investigation into shortening the follow up
period of clinical trials with a view to minimizing complications may be warranted.
We identified idiopathic post-stroke complications (deemed to be ‘stroke- unrelated’)
but their absence did not beneficially alter outcome at either 30 days (p<0.0001,
adjusted OR for good outcome =0.47, 95% CI [0.26, 0.67]), or 90 days (p=0.002, adjusted
OR for good outcome =0.38, 95% CI [0.14, 0.61]). We concluded that shortening the
follow up period with the aim of minimizing ‘stroke-unrelated’ complications did not
benefit functional outcome, however further investigation is required.
Chapter 5 illustrates the use of VISTA to investigate the natural history of complications
after intracerebral haemorrhage (ICH). Treatments available for ICH remain limited.
The use of haemostatic agents to promote local coagulation has had no significant
benefit on outcome. However promising results from a subgroup analysis of patients
from the FAST trial has raised the possibility of treatment with recombinant factor VIIa
(rFVIIa) in patients with ICH. We sought to document the natural history of
complications after ICH in order to inform safety in future trials of haemostatic agents
for ICH.
We found that the risk of thromboembolic complications after ICH was low (4 events
affecting 2% of patients). The absence of these thromboembolic complications did not
significantly affect the attainment of good functional outcome (p>0.05). The occurrence
of haemorrhagic expansion was common, affecting 14% of patients, and significantly
influenced attainment of good functional outcome at 90 days (p= p<0.0001, adjusted
odds ratio for good functional outcome=21.9, 95% confidence interval [5.5, 88.3]).
Although infection occurred in 11% of patients, this did not significantly influence
attainment of good functional outcome at 90 days (p=0.8). The complications
encountered in this investigation and their time to onset will serve to inform
prophylaxis in future ICH clinical trials.
Chapter 6 describes the processes involved in drug development from phase I, first- in –
man studies to phase III efficacy trials and identifies a key area in the drug development
process where use of VISTA as a historical comparator resource could be of benefit:
phase II studies. We detail here the types of conventional comparator groups available
for use in a phase II investigation, advantages and disadvantages of using each of these
comparator groups, the potential for use of historical comparators in some scenarios
where use of conventional comparator groups is infeasible, and possible solutions to
address the limitations associated with use of historical comparators.
Chapter 7 illustrates the use of VISTA as a resource for historical comparators in the
context of an acute stroke device trial conducted by a small company with limited
resources. BrainsGate, the manufacturers of the NeuroPath™ Device for treatment of
ischaemic stroke, sought to collaborate with the VISTA group to examine initial efficacy
of their device against outcomes derived from VISTA historical comparators. We discuss
the example of this device in early phase testing, where VISTA was primed for use as a
resource for historical comparators. We also describe the limitations associated with the
use of historical comparators, how these limitations could be overcome in practice
through use of matched patients, implementation of strict eligibility criteria and use of
similar follow up periods and stroke scales, as well as the measures taken to ensure the
validity of results.
Chapter 8 describes a collaboration with the DESTINY trial group to investigate stroke
outcomes after malignant middle cerebral artery occlusion (mMCAO). The DESTINY trial
examined the impact of decompressive hemicraniectomy on outcome after mMCAO,
compared with randomised controls. We compared the outcomes of operated patients
from the DESTINY trial with historical comparators from VISTA to determine whether
the findings could be replicated and if historical comparators could be used as an
alternative in a situation where a randomised controlled trial (RCT) is infeasible or
unethical.
We found that fewer patients in the VISTA comparator group achieved a good functional
outcome by mRS at final follow up (19%), when compared with the DESTINY surgical
group (47%, Chi- Square test p=0.04). This difference persisted after adjusting for
baseline NIHSS (logistic regression p=0.04). Analysis of Barthel Index at final follow up
revealed no significant difference between the two groups and we also found no
difference in 6 month survival rates between the surgical and VISTA comparator groups
(Cox Proportional Hazards model p>0.05). We concluded that for effective replication of
results, the database from which historical comparators are to be drawn should cover a
similar or broader spectrum of patient prognostic factors.
Chapter 9 discusses the implications of the investigations described in this thesis,
outlines the scope for expanding the resource and proposes areas for future research.

Item Type: Thesis (PhD)
Qualification Level: Doctoral
Keywords: Stroke, Clinical Trials, Resource, Database, Analyses, Trial Design
Subjects: R Medicine > R Medicine (General)
R Medicine > RZ Other systems of medicine
Colleges/Schools: College of Medical Veterinary and Life Sciences > Institute of Cardiovascular and Medical Sciences
Supervisor's Name: Lees, Prof. Kennedy R.
Date of Award: 2008
Depositing User: Miss Myzoon Ali
Unique ID: glathesis:2008-509
Copyright: Copyright of this thesis is held by the author.
Date Deposited: 18 Mar 2009
Last Modified: 10 Dec 2012 13:19
URI: http://theses.gla.ac.uk/id/eprint/509

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