Solitaire flow restoration device versus (1)
Articles
Solitaire flow restoration device versus the Merci Retriever in
patients with acute ischaemic stroke (SWIFT): a randomised,
parallel-group, non-inferiority trial
Jeffrey L Saver, Reza Jahan, Elad I Levy, Tudor G Jovin, Blaise Baxter, Raul G Nogueira, Wayne Clark, Ronald Budzik, Osama O Zaidat, for the
SWIFT Trialists
Summary
Background The Solitaire Flow Restoration Device is a novel, self-expanding stent retriever designed to yield rapid
flow restoration in acute cerebral ischaemia. We compared the efficacy and safety of Solitaire with the standard,
predicate mechanical thrombectomy device, the Merci Retrieval System.
Methods In this randomised, parallel-group, non-inferiority trial, we enrolled patients from 18 sites (17 in the USA
and one in France). Patients were eligible for inclusion if they had acute ischaemic stroke with moderate to severe
neurological deficits and were treatable by thrombectomy within 8 h of stroke symptom onset. We used a computergenerated randomisation sequence to randomly allocate patients to receive thrombectomy treatment with either
Solitaire or Merci (1:1; block sizes of four and stratified by centre and stroke severity). The primary endpoint was
Thrombolysis In Myocardial Ischemia (TIMI) scale 2 or 3 flow in all treatable vessels without symptomatic intracranial
haemorrhage, after up to three passes of the assigned device, as assessed by an independent core laboratory, which
was masked to study assignment. Primary analysis was done by intention to treat. A prespecified efficacy stopping
rule triggered an early halt to the trial. The study is registered with ClinicalTrials.gov, number NCT 01054560.
Results Between February, 2010, and February, 2011, we randomly allocated 58 patients to the Solitaire group and
55 patients to the Merci group. The primary efficacy outcome was achieved more often in the Solitaire group than it
was in the Merci group (61% vs 24%; difference 37% [95% CI 19–53], odds ratio [OR] 4·87 [95% CI 2·14–11·10];
pnon-inferiority17), with blocks sizes of four.
Allocation concealment was implemented by use of
sequentially numbered, opaque, sealed envelopes.
An independent central core imaging laboratory,
unaware of the study group assignments, assessed final
revascularisation grades on outcome angiograms and
haemorrhagic transformation on outcome CT and MR
1242
examinations. A central, independent clinical events
committee, whose members were unaware of the study
group assignments, categorised all adverse events by
severity and relatedness to the study device and to the
interventional procedure.
Procedures
Once a patient was assigned to either Solitaire or Merci,
the neurointerventionalist selected the proper study
device size per device-specific instructions for use. A
minimum of one deployment of the assigned study
device was required to be achieved within 8 h of symptom
onset. The neurointerventionalist attempted recanalisation using the assigned device type, continuing until
successful recanalisation was achieved or until three
passes of the study group device through any vessel had
been done. The primary endpoint outcome angiogram
was then done. Intravenous sedation or general
anaesthesia was allowed to be used, if deemed appropriate
by the attending neurointerventionalist, to assure the
comfort and safety of patients.
After the primary endpoint outcome angiogram was
done, rescue treatment was permitted in patients in
whom adequate recanalisation had not been achieved.
All cases requiring rescue treatment were regarded as
device treatment failures. Permitted rescue treatment
interventions were as follows: a regulatory-agencycleared neurovascular thrombectomy device different
than the initially assigned study device, intra-arterial
fibrinolysis according to US guidelines,4 or both. If any
rescue treatment had been done, an additional, final,
diagnostic angiogram (after all procedures had been
done) was obtained.
Follow-up assessment was done at 24 h, 7–10 days
(or discharge if earlier), 30 days, and 90 days. The
24-h assessment included a repeat NIHSS score and
repeat brain CT or MRI, allowing ascertainment of the
symptomatic intracranial haemorrhage component of
the composite primary endpoint. The later assessments
included the NIHSS, the Barthel Index assessing
instrumental activities of daily living, and the modified
Rankin Scale (mRS) assessing global disability.
The primary efficacy endpoint of the study was
successful recanalisation with the assigned study device
(no use of rescue treatment) and with no symptomatic
intracranial haemorrhage. Successful recanalisation was
defined as the achievement of Thrombolysis In Myocardial Ischemia (TIMI) scale 2 or 3 flow in all treatable
vessels.8 Successful recanalisation of the middle cerebral
artery required reperfusion through all M1 and M2
segments. Successful recanalisation of internal carotid
artery terminus lesions required reperfusion through the
internal carotid artery and all M1 and M2 branches.
Successful recanalisation of a vertebral artery required
reperfusion through both the target vertebral artery and
the basilar artery. Symptomatic intracranial haemorrhage was defined as any parenchymal haematoma,
www.thelancet.com Vol 380 October 6, 2012
Articles
subarachnoid haemorrhage, or intraventricular haemorrhage associated with a worsening of the NIHSS score by
four or more within 24 h.
Secondary efficacy outcomes included the following:
time to achieve initial recanalisation, defined as the time
from baseline guide catheter run to visualisation of TIMI
2 or 3 flow in all treatable vessels; good neurological
outcome at 90 days, defined as an mRS of 2 or less, or
equal to the prestroke mRS if the prestroke mRS was
greater than 2, or NIHSS score improvement of 10 points
or more; and neurological condition at 90 days, including
NIHSS, Barthel Index, and mRS. The primary safety
endpoint was the incidence of device-related and
procedure-related serious adverse events. Additional
safety endpoints included mortality and symptomatic
intracranial haemorrhage.
Statistical analysis
We designed the trial to show that the proportion of
patients with successful recanalisation with no symptomatic haemorrhage would be non-inferior in the
Solitaire group compared with the control group, the
Merci group, using a clinically relevant non-inferiority
margin that was defined before starting the trial to be
10%. Superiority analysis of the primary endpoint was
undertaken only if non-inferiority was achieved. Efficacy
endpoints were assessed in the intention-to-treat
population, which included all patients who consented
and were randomly assigned to treatment. We did the
primary efficacy analysis using a one-sided test under
Blackwelder’s method of testing non-inferiority at the
0·025 level of significance.20 We did the nested superiority
analysis using a two-sided test at the 0·05 level of
537 patients assessed for eligibility
391 excluded
359 did not meet entry criteria
11 unable to consent
21 other reasons
32 roll-in patients
32 allocated to SOLITAIRE
32 received allocated intervention
114 randomly assigned
58 allocated to Solitaire
58 received allocated intervention
56 allocated to Merci
56 received allocated intervention
1 no HIPAA
1 no HIPAA
29 primary endpoint angiographic
data available from core laboratory
(2 angiographic data not available)
56 primary endpoint angiographic data
available from core laboratory
(2 angiographic data not available)
54 primary endpoint angiographic data
available from core laboratory
(1 angiographic data not available)
29 in primary analysis
56 in primary analysis
54 in primary analysis
31 in sensitivity analysis
58 in sensitivity analysis (missing data
as failures)
55 in sensitivity analysis (missing data
as failures)
27 died or completed 90-day follow-up
(4 lost to follow-up)
31 in sensitivity analysis one (imputed as
failure)
31 in sensitivity two (last observation
carried forward)
55 died or completed 90-day follow-up
(2 lost to follow-up, 1 withdrawn by
investigator)
58 in sensitivity analysis one (imputed as
failure)
58 in sensitivity two (last observation
carried forward)
48 died or completed 90-day follow-up
(5 lost to follow-up, 2 withdrew)
55 in sensitivity analysis one (imputed as
failure)
55 in sensitivity two (last observation
carried forward)
Figure 1: Trial profile
Two patients signed study consents but not Health Insurance Portability and Accountability Act (HIPAA) consents, including one roll-in patient and one patient
randomly allocated to treatment. These patients were excluded from all analyses. Angiographic outcome images forwarded to the core laboratory were insufficient to
allow Thrombolysis In Myocardial Ischemia outcome assessment in two roll-in and three randomised patients. These patients were censored in the primary analysis. In
sensitivity analyses, they were analysed as failures in analysis one, and according to site readings in analysis two.
www.thelancet.com Vol 380 October 6, 2012
1243
Articles
significance. We did a sensitivity analysis to assess the
effect of any between-group differences in baseline
features on the primary efficacy endpoint, using univariate
logistic regression of variables with a p value of 0·1 or less
reduced to a final model by backward elimination, with
variables used as randomisation stratification factors
required to be included. For secondary efficacy endpoint
analyses, statistical tests of non-inferiority were one-sided
Solitaire
(roll-in; n=31)
Merci (randomly
Solitaire
allocated; n=55)
(randomly
allocated; n=58)
Age (years; mean [SD])
65·4 (14·5)
67·1 (12·0)
67·1 (11·1)
Sex (% male)
42%
48%
51%
Mean (SD)
17·5 (4·6)
17·3 (4·5)
17·4 (4·8)
Median (range)
18·0 (8·0–26·0)
18·0 (9·0–28·0)
18·0 (8·0–26·0)
≤17 (%)
45%
48%
47%
NIHSS score
Pre-stroke modified Rankin Scale
Median (range)
2 or better
0 (0–4)
0 (0–3)
0 (0–5)
84%
96%
94%
Body-mass index (mean [SD])
29·9 (9·4)
29·3 (6·8)
29·4 (5·5)
Intravenous rt-PA failure
74%
33%
47%
69%
Medical history
Hypertension
55%
72%
Diabetes mellitus
32%
24%
31%
Hyperlipidaemia
52%
53%
56%
Current or ex-smoker
36%
40%
40%
Atrial fibrillation
39%
45%
67%
Myocardial infarction
36%
33%
35%
Peripheral arterial disease
10%
2%
7%
10%
14%
18%
Haemorrhagic stroke
3%
2%
9%
Transient ischaemic attack
5%
6%
5%
Visual disturbance
7%
0%
9%
Motor disturbance
10%
5%
6%
Sudden numbness
94%
97%
96%
Sudden confusion
68%
57%
82%
Sudden trouble seeing
29%
22%
33%
Sudden trouble walking
32%
36%
36%
Sudden severe headache
0%
9%
2%
25%
Stroke symptoms at presentation
Most proximal occlusion location
Internal carotid artery
22%
21%
M1 middle cerebral artery
61%
66%
51%
M2 middle cerebral artery
13%
10%
19%
Posterior circulation
6%
2%
2%
Other
0%
2%
4%
47%
47%
48%
Occlusion side (left)
Largest occluded vessel size (mm; mean [SD])
3·0 (1·0)
2·9 (0·9)
2·8 (0·9)
Time to arterial puncture (min; mean [SD])
301·6 (71·2)
293·5 (85·6)
319·9 (88·1)
NIHSS=National Institutes of Health Stroke Scale. rt-PA=recombinant tissue plasminogen activator.
Table 1: Baseline demographic and clinical characteristics of the patients
1244
Role of the funding source
An academic principal investigator (JLS), academic lead
interventional investigator (RJ), and academic steering
committee supervised trial design and operations. A
publications committee (principal investigator, lead
interventional investigator, steering committee, and
academic principal investigators the sites that enrolled
most patients interpreted the results and wrote the
report. The sponsor of the study was responsible for site
management, data management, and safety reporting.
Key statistical analyses, including the primary endpoint
analysis, were validated by an independent external
statistician (J Schafer, MS, Integra Group, Brooklyn Park,
MN, USA). The corresponding author had full access to
all the data in the study and had final responsibility for
the decision to submit for publication.
Results
Neurological history
Previous ischaemic stroke
and all other tests were two-sided. Resulting p values are
shown without multiplicity adjustment.
We calculated the sample size by assuming that the true
proportions of patients with successful recanalisation
without symptomatic intracranial haemorrhage would be
0·54 in the Merci group and 0·65 in the Solitaire group. A
total of 174 assessable patients for this endpoint would
give 80% power and a final sample size of 200 was selected
to ensure the recruitment of at least 174 assessable
patients.20 We planned one formal interim efficacy analysis
according to the method of alpha-spending of Lan-DeMets
using a Pocock-type alpha-spending function.
The trial is registered with ClinicalTrials.gov, number
NCT 01054560.
Between February, 2010, and February, 2011, 18 sites
(17 in the USA and one in France) consented and
enrolled 144 patients, including 31 roll-in patients who
received Solitaire and 113 patients who were randomly
allocated to one of the two treatment groups (58 to
Solitaire and 55 to Merci; figure 1). After a safety review
in February, 2011, the data and safety monitoring board
recommended that enrolment be placed on hold and the
interim efficacy analysis be undertaken earlier than
initially planned. In September, 2011, after the interim
efficacy analysis was done and pre-specified criteria on
which to stop the trial were met, the data safety and
monitoring board recommended halting the trial, and
the trial steering committee concurred.
Baseline demographic and clinical characteristics of
the two randomised treatment groups were much the
same across 35 variables, including age and presenting
stroke severity (NIHSS), except that there were more
patients with atrial fibrillation, history of previous visual
disturbance, and presentation with confusion in the
Merci group (before adjustment for multiple comparisons; table 1).
The mean number of passes with the assigned study
device was lower in the Solitaire group than it was in the
www.thelancet.com Vol 380 October 6, 2012
Articles
Solitaire
(roll-in; n=31)
Odds ratio
Merci
Solitaire
(95% CI) for
(randomly
(randomly
allocated; n=58) allocated; n=55) comparison
between
randomised
groups
Non-inferiority
p value for
comparison
between
randomised
groups
Superiority
p value for
randomised
comparison
55% (16/29)
61% (34/56)
24% (13/54)
4·87 (2·14–11·10)
Solitaire flow restoration device versus the Merci Retriever in
patients with acute ischaemic stroke (SWIFT): a randomised,
parallel-group, non-inferiority trial
Jeffrey L Saver, Reza Jahan, Elad I Levy, Tudor G Jovin, Blaise Baxter, Raul G Nogueira, Wayne Clark, Ronald Budzik, Osama O Zaidat, for the
SWIFT Trialists
Summary
Background The Solitaire Flow Restoration Device is a novel, self-expanding stent retriever designed to yield rapid
flow restoration in acute cerebral ischaemia. We compared the efficacy and safety of Solitaire with the standard,
predicate mechanical thrombectomy device, the Merci Retrieval System.
Methods In this randomised, parallel-group, non-inferiority trial, we enrolled patients from 18 sites (17 in the USA
and one in France). Patients were eligible for inclusion if they had acute ischaemic stroke with moderate to severe
neurological deficits and were treatable by thrombectomy within 8 h of stroke symptom onset. We used a computergenerated randomisation sequence to randomly allocate patients to receive thrombectomy treatment with either
Solitaire or Merci (1:1; block sizes of four and stratified by centre and stroke severity). The primary endpoint was
Thrombolysis In Myocardial Ischemia (TIMI) scale 2 or 3 flow in all treatable vessels without symptomatic intracranial
haemorrhage, after up to three passes of the assigned device, as assessed by an independent core laboratory, which
was masked to study assignment. Primary analysis was done by intention to treat. A prespecified efficacy stopping
rule triggered an early halt to the trial. The study is registered with ClinicalTrials.gov, number NCT 01054560.
Results Between February, 2010, and February, 2011, we randomly allocated 58 patients to the Solitaire group and
55 patients to the Merci group. The primary efficacy outcome was achieved more often in the Solitaire group than it
was in the Merci group (61% vs 24%; difference 37% [95% CI 19–53], odds ratio [OR] 4·87 [95% CI 2·14–11·10];
pnon-inferiority17), with blocks sizes of four.
Allocation concealment was implemented by use of
sequentially numbered, opaque, sealed envelopes.
An independent central core imaging laboratory,
unaware of the study group assignments, assessed final
revascularisation grades on outcome angiograms and
haemorrhagic transformation on outcome CT and MR
1242
examinations. A central, independent clinical events
committee, whose members were unaware of the study
group assignments, categorised all adverse events by
severity and relatedness to the study device and to the
interventional procedure.
Procedures
Once a patient was assigned to either Solitaire or Merci,
the neurointerventionalist selected the proper study
device size per device-specific instructions for use. A
minimum of one deployment of the assigned study
device was required to be achieved within 8 h of symptom
onset. The neurointerventionalist attempted recanalisation using the assigned device type, continuing until
successful recanalisation was achieved or until three
passes of the study group device through any vessel had
been done. The primary endpoint outcome angiogram
was then done. Intravenous sedation or general
anaesthesia was allowed to be used, if deemed appropriate
by the attending neurointerventionalist, to assure the
comfort and safety of patients.
After the primary endpoint outcome angiogram was
done, rescue treatment was permitted in patients in
whom adequate recanalisation had not been achieved.
All cases requiring rescue treatment were regarded as
device treatment failures. Permitted rescue treatment
interventions were as follows: a regulatory-agencycleared neurovascular thrombectomy device different
than the initially assigned study device, intra-arterial
fibrinolysis according to US guidelines,4 or both. If any
rescue treatment had been done, an additional, final,
diagnostic angiogram (after all procedures had been
done) was obtained.
Follow-up assessment was done at 24 h, 7–10 days
(or discharge if earlier), 30 days, and 90 days. The
24-h assessment included a repeat NIHSS score and
repeat brain CT or MRI, allowing ascertainment of the
symptomatic intracranial haemorrhage component of
the composite primary endpoint. The later assessments
included the NIHSS, the Barthel Index assessing
instrumental activities of daily living, and the modified
Rankin Scale (mRS) assessing global disability.
The primary efficacy endpoint of the study was
successful recanalisation with the assigned study device
(no use of rescue treatment) and with no symptomatic
intracranial haemorrhage. Successful recanalisation was
defined as the achievement of Thrombolysis In Myocardial Ischemia (TIMI) scale 2 or 3 flow in all treatable
vessels.8 Successful recanalisation of the middle cerebral
artery required reperfusion through all M1 and M2
segments. Successful recanalisation of internal carotid
artery terminus lesions required reperfusion through the
internal carotid artery and all M1 and M2 branches.
Successful recanalisation of a vertebral artery required
reperfusion through both the target vertebral artery and
the basilar artery. Symptomatic intracranial haemorrhage was defined as any parenchymal haematoma,
www.thelancet.com Vol 380 October 6, 2012
Articles
subarachnoid haemorrhage, or intraventricular haemorrhage associated with a worsening of the NIHSS score by
four or more within 24 h.
Secondary efficacy outcomes included the following:
time to achieve initial recanalisation, defined as the time
from baseline guide catheter run to visualisation of TIMI
2 or 3 flow in all treatable vessels; good neurological
outcome at 90 days, defined as an mRS of 2 or less, or
equal to the prestroke mRS if the prestroke mRS was
greater than 2, or NIHSS score improvement of 10 points
or more; and neurological condition at 90 days, including
NIHSS, Barthel Index, and mRS. The primary safety
endpoint was the incidence of device-related and
procedure-related serious adverse events. Additional
safety endpoints included mortality and symptomatic
intracranial haemorrhage.
Statistical analysis
We designed the trial to show that the proportion of
patients with successful recanalisation with no symptomatic haemorrhage would be non-inferior in the
Solitaire group compared with the control group, the
Merci group, using a clinically relevant non-inferiority
margin that was defined before starting the trial to be
10%. Superiority analysis of the primary endpoint was
undertaken only if non-inferiority was achieved. Efficacy
endpoints were assessed in the intention-to-treat
population, which included all patients who consented
and were randomly assigned to treatment. We did the
primary efficacy analysis using a one-sided test under
Blackwelder’s method of testing non-inferiority at the
0·025 level of significance.20 We did the nested superiority
analysis using a two-sided test at the 0·05 level of
537 patients assessed for eligibility
391 excluded
359 did not meet entry criteria
11 unable to consent
21 other reasons
32 roll-in patients
32 allocated to SOLITAIRE
32 received allocated intervention
114 randomly assigned
58 allocated to Solitaire
58 received allocated intervention
56 allocated to Merci
56 received allocated intervention
1 no HIPAA
1 no HIPAA
29 primary endpoint angiographic
data available from core laboratory
(2 angiographic data not available)
56 primary endpoint angiographic data
available from core laboratory
(2 angiographic data not available)
54 primary endpoint angiographic data
available from core laboratory
(1 angiographic data not available)
29 in primary analysis
56 in primary analysis
54 in primary analysis
31 in sensitivity analysis
58 in sensitivity analysis (missing data
as failures)
55 in sensitivity analysis (missing data
as failures)
27 died or completed 90-day follow-up
(4 lost to follow-up)
31 in sensitivity analysis one (imputed as
failure)
31 in sensitivity two (last observation
carried forward)
55 died or completed 90-day follow-up
(2 lost to follow-up, 1 withdrawn by
investigator)
58 in sensitivity analysis one (imputed as
failure)
58 in sensitivity two (last observation
carried forward)
48 died or completed 90-day follow-up
(5 lost to follow-up, 2 withdrew)
55 in sensitivity analysis one (imputed as
failure)
55 in sensitivity two (last observation
carried forward)
Figure 1: Trial profile
Two patients signed study consents but not Health Insurance Portability and Accountability Act (HIPAA) consents, including one roll-in patient and one patient
randomly allocated to treatment. These patients were excluded from all analyses. Angiographic outcome images forwarded to the core laboratory were insufficient to
allow Thrombolysis In Myocardial Ischemia outcome assessment in two roll-in and three randomised patients. These patients were censored in the primary analysis. In
sensitivity analyses, they were analysed as failures in analysis one, and according to site readings in analysis two.
www.thelancet.com Vol 380 October 6, 2012
1243
Articles
significance. We did a sensitivity analysis to assess the
effect of any between-group differences in baseline
features on the primary efficacy endpoint, using univariate
logistic regression of variables with a p value of 0·1 or less
reduced to a final model by backward elimination, with
variables used as randomisation stratification factors
required to be included. For secondary efficacy endpoint
analyses, statistical tests of non-inferiority were one-sided
Solitaire
(roll-in; n=31)
Merci (randomly
Solitaire
allocated; n=55)
(randomly
allocated; n=58)
Age (years; mean [SD])
65·4 (14·5)
67·1 (12·0)
67·1 (11·1)
Sex (% male)
42%
48%
51%
Mean (SD)
17·5 (4·6)
17·3 (4·5)
17·4 (4·8)
Median (range)
18·0 (8·0–26·0)
18·0 (9·0–28·0)
18·0 (8·0–26·0)
≤17 (%)
45%
48%
47%
NIHSS score
Pre-stroke modified Rankin Scale
Median (range)
2 or better
0 (0–4)
0 (0–3)
0 (0–5)
84%
96%
94%
Body-mass index (mean [SD])
29·9 (9·4)
29·3 (6·8)
29·4 (5·5)
Intravenous rt-PA failure
74%
33%
47%
69%
Medical history
Hypertension
55%
72%
Diabetes mellitus
32%
24%
31%
Hyperlipidaemia
52%
53%
56%
Current or ex-smoker
36%
40%
40%
Atrial fibrillation
39%
45%
67%
Myocardial infarction
36%
33%
35%
Peripheral arterial disease
10%
2%
7%
10%
14%
18%
Haemorrhagic stroke
3%
2%
9%
Transient ischaemic attack
5%
6%
5%
Visual disturbance
7%
0%
9%
Motor disturbance
10%
5%
6%
Sudden numbness
94%
97%
96%
Sudden confusion
68%
57%
82%
Sudden trouble seeing
29%
22%
33%
Sudden trouble walking
32%
36%
36%
Sudden severe headache
0%
9%
2%
25%
Stroke symptoms at presentation
Most proximal occlusion location
Internal carotid artery
22%
21%
M1 middle cerebral artery
61%
66%
51%
M2 middle cerebral artery
13%
10%
19%
Posterior circulation
6%
2%
2%
Other
0%
2%
4%
47%
47%
48%
Occlusion side (left)
Largest occluded vessel size (mm; mean [SD])
3·0 (1·0)
2·9 (0·9)
2·8 (0·9)
Time to arterial puncture (min; mean [SD])
301·6 (71·2)
293·5 (85·6)
319·9 (88·1)
NIHSS=National Institutes of Health Stroke Scale. rt-PA=recombinant tissue plasminogen activator.
Table 1: Baseline demographic and clinical characteristics of the patients
1244
Role of the funding source
An academic principal investigator (JLS), academic lead
interventional investigator (RJ), and academic steering
committee supervised trial design and operations. A
publications committee (principal investigator, lead
interventional investigator, steering committee, and
academic principal investigators the sites that enrolled
most patients interpreted the results and wrote the
report. The sponsor of the study was responsible for site
management, data management, and safety reporting.
Key statistical analyses, including the primary endpoint
analysis, were validated by an independent external
statistician (J Schafer, MS, Integra Group, Brooklyn Park,
MN, USA). The corresponding author had full access to
all the data in the study and had final responsibility for
the decision to submit for publication.
Results
Neurological history
Previous ischaemic stroke
and all other tests were two-sided. Resulting p values are
shown without multiplicity adjustment.
We calculated the sample size by assuming that the true
proportions of patients with successful recanalisation
without symptomatic intracranial haemorrhage would be
0·54 in the Merci group and 0·65 in the Solitaire group. A
total of 174 assessable patients for this endpoint would
give 80% power and a final sample size of 200 was selected
to ensure the recruitment of at least 174 assessable
patients.20 We planned one formal interim efficacy analysis
according to the method of alpha-spending of Lan-DeMets
using a Pocock-type alpha-spending function.
The trial is registered with ClinicalTrials.gov, number
NCT 01054560.
Between February, 2010, and February, 2011, 18 sites
(17 in the USA and one in France) consented and
enrolled 144 patients, including 31 roll-in patients who
received Solitaire and 113 patients who were randomly
allocated to one of the two treatment groups (58 to
Solitaire and 55 to Merci; figure 1). After a safety review
in February, 2011, the data and safety monitoring board
recommended that enrolment be placed on hold and the
interim efficacy analysis be undertaken earlier than
initially planned. In September, 2011, after the interim
efficacy analysis was done and pre-specified criteria on
which to stop the trial were met, the data safety and
monitoring board recommended halting the trial, and
the trial steering committee concurred.
Baseline demographic and clinical characteristics of
the two randomised treatment groups were much the
same across 35 variables, including age and presenting
stroke severity (NIHSS), except that there were more
patients with atrial fibrillation, history of previous visual
disturbance, and presentation with confusion in the
Merci group (before adjustment for multiple comparisons; table 1).
The mean number of passes with the assigned study
device was lower in the Solitaire group than it was in the
www.thelancet.com Vol 380 October 6, 2012
Articles
Solitaire
(roll-in; n=31)
Odds ratio
Merci
Solitaire
(95% CI) for
(randomly
(randomly
allocated; n=58) allocated; n=55) comparison
between
randomised
groups
Non-inferiority
p value for
comparison
between
randomised
groups
Superiority
p value for
randomised
comparison
55% (16/29)
61% (34/56)
24% (13/54)
4·87 (2·14–11·10)