CLINICAL PHARMACOLOGY
Mechanism Of Action
In MRI, visualization of normal and pathological tissue depends in part on variations in the radiofrequency signal
intensity that occurs with:
- Differences in proton density
- Differences of the spin-lattice or longitudinal relaxation times (T1)
- Differences in the spin-spin or transverse relaxation time (T2)
When placed in a magnetic field, Gadavist shortens the T1 and T2 relaxation times. The extent of decrease of T1 and T2
relaxation times, and therefore the amount of signal enhancement obtained from Gadavist, is based upon several factors
including the concentration of Gadavist in the tissue, the field strength of the MRI system, and the relative ratio of the
longitudinal and transverse relaxation times. At the recommended dose, the T1 shortening effect is observed with greatest
sensitivity in T1-weighted magnetic resonance sequences. In T2*-weighted sequences the induction of local magnetic
field inhomogeneities by the large magnetic moment of gadolinium and at high concentrations (during bolus injection)
leads to a signal decrease.
Pharmacodynamics
Gadavist leads to distinct shortening of the relaxation times even in low concentrations. At pH 7, 37°C and 1.5 T, the
relaxivity (r1) - determined from the influence on the relaxation times (T1) of protons in plasma - is 5.2 L/(mmol·sec) and
the relaxivity (r2) - determined from the influence on the relaxation times (T2) - is 6.1 L/(mmol·sec). These relaxivities
display only slight dependence on the strength of the magnetic field. The T1 shortening effect of paramagnetic contrast
agents is dependent on concentration and r1 relaxivity (see Table 3). This may improve tissue visualization.
Table 3: Relaxivity (r1) of Gadolinium Chelates at 1.5 T
Gadolinium-Chelate |
r1 (L·mmol -1 ·s -1) |
Gadobenate |
6.3 |
Gadobutrol |
5.2 |
Gadodiamide |
4.3 |
Gadofosveset |
16 |
Gadopentetate |
4.1 |
Gadoterate |
3.6 |
Gadoteridol |
4.1 |
Gadoversetamide |
4.7 |
Gadoxetate |
6.9 |
r1 relaxivity in plasma at 37°C |
Compared to 0.5 molar gadolinium-based contrast agents, the higher concentration of Gadavist results in half the volume
of administration and a more compact contrast bolus injection. At the site of imaging, the relative height and width of the
time intensity curve for Gadavist varies as a function of imaging location and multiple patient, injection, and devicespecific
factors.
Gadavist is a water-soluble, hydrophilic compound with a partition coefficient between n-butanol and buffer at pH 7.6 of
about 0.006.
Pharmacokinetics
Distribution
After intravenous administration, gadobutrol is rapidly distributed in the extracellular space. After a gadobutrol dose of
0.1 mmol/kg body weight, an average level of 0.59 mmol gadobutrol/L was measured in plasma 2 minutes after the
injection and 0.3 mmol gadobutrol/L 60 minutes after the injection. Gadobutrol does not display any particular protein
binding. Following GBCA administration, gadolinium is present for months or years in brain, bone, skin, and other organs
[see WARNINGS AND PRECAUTIONS].
Metabolism
Gadobutrol is not metabolized.
Elimination
Values for AUC, body weight normalized plasma clearance and half-life are given in Table 4, below.
Gadobutrol is excreted in an unchanged form via the kidneys. In healthy subjects, renal clearance of gadobutrol is 1.1 to
1.7 mL/(min·kg) and thus comparable to the renal clearance of inulin, confirming that gadobutrol is eliminated by
glomerular filtration.
Within two hours after intravenous administration more than 50% and within 12 hours more than 90% of the given dose is
eliminated via the urine. Extra-renal elimination is negligible.
Specific Populations
Gender
Gender has no clinically relevant effect on the pharmacokinetics of gadobutrol.
Geriatric
A single IV dose of 0.1 mmol/kg Gadavist was administered to 15 elderly and 16 non-elderly subjects. AUC was slightly
higher and clearance slightly lower in elderly subjects as compared to non-elderly subjects [see Use In Specific Populations].
Pediatric
The pharmacokinetics of gadobutrol were evaluated in two studies in a total of 130 patients age 2 to less than 18 years and
in 43 patients less than 2 years of age (including term neonates). Patients received a single intravenous dose of 0.1
mmol/kg of Gadavist. The pharmacokinetic profile of gadobutrol in pediatric patients is similar to that in adults, resulting
in similar values for AUC, body weight normalized plasma clearance, as well as elimination half-life. Approximately 99%
(median value) of the dose was recovered in urine within 6 hours (this information was derived from the 2 to less than 18
year old age group).
Table 4: Pharmacokinetics by Age Group (Median [Range])
|
0 to < 2 years
N=43 |
2 to 6 years
N=45 |
7 to 11 years
N=39 |
12 to < 18 years
N=46 |
Adults
N=93 |
AUC (μmolxh/L) |
781
[513, 1891] |
846
[412, 1331] |
1025
[623, 2285] |
1237
[946, 2211] |
1072
[667, 1992] |
CL (L/h/kg) |
0.128
[0.053, 0.195] |
0.119
[0.080, 0.215] |
0.099
[0.043, 0.165] |
0.081
[0.046, 0.103] |
0.094
[0.051, 0.150] |
t1/2 (h) |
2.91
[1.60, 12.4] |
1.91
[1.04, 2.70] |
1.66
[0.91, 2.71] |
1.68
[1.31, 2.48] |
1.80
[1.20, 6.55] |
C20 (μmol/L) |
367
[280, 427] |
421
[369, 673] |
462
[392, 760] |
511
[387, 1077] |
441
[281, 829] |
Renal Impairment
In patients with impaired renal function, the serum half-life of gadobutrol is prolonged and correlated with the reduction
in creatinine clearance.
After intravenous injection of 0.1 mmol gadobutrol/kg body weight, the elimination half-life was 5.8 ± 2.4 hours in mild
to moderately impaired patients (80 > CLCR > 30 mL/min) and 17.6 ± 6.2 hours in severely impaired patients not on
dialysis (CLCR < 30 mL/min). The mean AUC of gadobutrol in patients with normal renal function was 1.1 ± 0.1
mmol·h/L, compared to 4.0 ± 1.8 mmol·h/L in patients with mild to moderate renal impairment and 11.5 ± 4.3 mmol·h/L
in patients with severe renal impairment.
Complete recovery in the urine was seen in patients with mild or moderate renal impairment within 72 hours. In patients
with severely impaired renal function about 80% of the administered dose was recovered in the urine within 5 days.
For patients receiving hemodialysis, physicians may consider the prompt initiation of hemodialysis following the
administration of Gadavist in order to enhance the contrast agent’s elimination. Sixty-eight percent (68%) of gadobutrol is
removed from the body after the first dialysis, 94% after the second dialysis, and 98% after the third dialysis session. [see WARNINGS AND PRECAUTIONS and Use In Specific Populations]
Animal Toxicology And/Or Pharmacology
Local intolerance reactions, including moderate irritation associated with infiltration of inflammatory cells was observed
after paravenous administration to rabbits, suggesting the possibility of occurrence of local irritation if the contrast
medium leaks around veins in a clinical setting [see WARNINGS AND PRECAUTIONS].
Clinical Studies
MRI Of The CNS
Patients referred for MRI of the central nervous system with contrast were enrolled in two clinical trials that evaluated the
visualization characteristics of lesions. In both studies, patients underwent a baseline, pre-contrast MRI prior to
administration of Gadavist at a dose of 0.1 mmol/kg, followed by a post-contrast MRI. In Study A, patients also
underwent an MRI before and after the administration of gadoteridol. The studies were designed to demonstrate
superiority of Gadavist MRI to non-contrast MRI for lesion visualization. For both studies, pre-contrast and pre-plus-post
contrast images (paired images) were independently evaluated by three readers for contrast enhancement and border
delineation using a scale of 1 to 4, and for internal morphology using a scale of 1 to 3 (Table 5). Lesion counting was also
performed to demonstrate non-inferiority of paired Gadavist image sets to pre-contrast MRI. Readers were blinded to
clinical information.
Table 5: Primary Endpoint Visualization Scoring System
Score |
Visualization Characteristics |
Contrast Enhancement |
Border Delineation |
Internal Morphology |
1 |
None |
None |
Poorly visible |
2 |
Weak |
Moderate |
Moderately visible |
3 |
Clear |
Clear but incomplete |
Sufficiently visible |
4 |
Clear and bright |
Clear and complete |
N/A |
Efficacy was determined in 657 subjects. The average age was 49 years (range 18 to 85 years) and 42% were male. The
ethnic representations were 39% Caucasian, 4% Black, 16% Hispanic, 38% Asian, and 3% of other ethnic groups.
Table 6 shows a comparison of visualization results between paired images and pre-contrast images. Gadavist provided a
statistically significant improvement for each of the three lesion visualization parameters when averaged across three
independent readers for each study.
Table 6: Visualization Endpoint Results of Central Nervous System Adult MRI Studies with 0.1 mmol/kg Gadavist
Endpoint |
Study A
N=336 |
Study B
N=321 |
Pre-contrast |
Paired |
Difference1 |
Pre-contrast |
Paired |
Difference |
Contrast Enhancement |
0.97 |
2.26 |
1.292 |
0.93 |
2.86 |
1.942 |
Border Delineation |
1.98 |
2.58 |
0.602 |
1.92 |
2.94 |
1.022 |
Internal Morphology |
1.32 |
1.93 |
0.602 |
1.57 |
2.35 |
0.782 |
Average # Lesions Detected |
8.08 |
8.25 |
0.174 |
2.65 |
2.97 |
0.323 |
1 Difference of means = (paired mean) – (pre-contrast mean)
2 p<0.001
3 Met noninferiority margin of -0.35
4 Did not meet noninferiority margin of -0.35 |
Performances of Gadavist and gadoteridol for visualization parameters were similar. Regarding the number of lesions
detected, Study B met the prespecified noninferiority margin of -0.35 for paired read versus pre-contrast read while in
Study A, Gadavist and gadoteridol did not.
For the visualization endpoints contrast enhancement, border delineation, and internal morphology, the percentage of
patients scoring higher for paired images compared to pre-contrast images ranged from 93% to 99% for Study A, and 95%
to 97% for Study B. For both studies, the mean number of lesions detected on paired images exceeded that of the precontrast
images; 37% for Study A and 24% for Study B. There were 29% and 11% of subjects in which the pre-contrast
images detected more lesions for Study A and Study B, respectively.
The percentage of patients whose average reader mean score changed by ≤ 0, up to 1, up to 2, and ≥ 2 scoring categories
presented in Table 5 is shown in Table 7. The categorical improvement of (≤ 0) represents higher (< 0) or identical (= 0)
scores for the pre-contrast read, the categories with scores > 0 represent the magnitude of improvement seen for the paired
read.
Table 7: Primary Endpoint Visualization Categorical Improvement for Average Reader
Endpoint |
Study A
N=336 |
Study B
N=321 |
Categorical Improvement
(Paired – Pre-Contrast) % |
Categorical Improvement
(Paired – Pre-Contrast) % |
|
≤ 0 |
> 0 – < 1 |
1 – < 2 |
≥ 2 |
≤ 0 |
> 0 – < 1 |
1 – < 2 |
≥ 2 |
Contrast
Enhancement |
1 |
30 |
55 |
13 |
3 |
6 |
34 |
57 |
Border Delineation |
7 |
73 |
18 |
1 |
5 |
38 |
51 |
5 |
Internal Morphology |
4 |
79 |
17 |
0 |
5 |
61 |
33 |
1 |
For both studies, the improvement of visualization endpoints in paired Gadavist images compared to pre-contrast images
resulted in improved assessment of normal and abnormal CNS anatomy.
Pediatric Patients
Two studies in 44 pediatric patients age younger than 2 years and 135 pediatric patients age 2 to less than 18 years with
CNS and non-CNS lesions supported extrapolation of adult CNS efficacy findings. For example, comparing pre vs paired
pre- and post-contrast images, investigators selected the best of four descriptors under the heading, “Visualization of
lesion-internal morphology (lesion characterization) or homogeneity of vessel enhancement” for 27/44 (62% = pre) vs
43/44 (98% = paired) MR images from patients age 0 to less than 2 years and 106/135 (78% = pre) vs 108/135 (80% =
paired) MR images from patients age 2 to less than 18 years.
MRI Of The Breast
Patients with recently diagnosed breast cancer were enrolled in two identical clinical trials to evaluate the ability of
Gadavist to assess the presence and extent of malignant breast disease prior to surgery. Patients underwent non-contrast
breast MRI (BMR) prior to Gadavist (0.1 mmol/kg) breast MRI. BMR images and Gadavist BMR (combined contrast
plus non-contrast) images were independently evaluated in each study by three readers blinded to clinical information. In
separate reading sessions the BMR images and Gadavist BMR images were also interpreted together with X-ray
mammography images (XRM).
The studies evaluated 787 patients: Study 1 enrolled 390 women with an average age of 56 years, 74% were white, 25%
Asian, 0.5% black, and 0.5% other; Study 2 enrolled 396 women and 1 man with an average age of 57 years, 71% were
white, 24% Asian, 3% black, and 2% other.
The readers assessed 5 regions per breast for the presence of malignancy using each reading modality. The readings were
compared to an independent standard of truth (SoT) consisting of histopathology for all regions where excisions were
made and tissue evaluated. XRM plus ultrasound was used for all other regions.
The assessment of malignant disease was performed using a region based within-subject sensitivity. Sensitivity for each
reading modality was defined as the mean of the percentage of malignant breast regions correctly interpreted for each
subject. The within-subject sensitivity of Gadavist BMR was superior to that of BMR. The lower bound of the 95%
Confidence Interval (CI) for the difference in within-subject sensitivity ranged from 19% to 42% for Study 1 and from
12% to 27% for Study 2. The within-subject sensitivity for Gadavist BMR and BMR as well as for Gadavist BMR plus
XRM and BMR plus XRM is presented in Table 8.
Table 8: Sensitivity of Gadavist BMR for Detection of Malignant Breast Disease
Study 1 |
Study 2 |
Sensitivity (%)
N=388 Patients |
Sensitivity (%)
N=390 Patients |
Reader |
BMR |
BMR + XRM |
Gadavist BMR |
Gadavist BMR +XRM |
Reader |
BMR |
BMR + XRM |
Gadavist BMR |
Gadavist BMR +XRM |
1 |
37 |
71 |
83 |
84 |
4 |
73 |
83 |
87 |
90 |
2 |
49 |
76 |
80 |
83 |
5 |
57 |
81 |
89 |
90 |
3 |
63 |
75 |
87 |
87 |
6 |
55 |
80 |
86 |
88 |
Specificity was defined as the percentage of non-malignant breasts correctly identified as non-malignant. The lower limit
of the 95% confidence interval for specificity of Gadavist BMR was greater than 80% for 5 of 6 readers. (Table 9)
Table 9: Specificity of Gadavist BMR in Non-Malignant Breasts
Study 1 |
Study 2 |
Specificity (%)
N=372 Patients |
Specificity (%)
N=367 Patients |
Reader |
Gadavist
BMR |
Lower Limit
95% CI |
Reader |
Gadavist
BMR |
Lower Limit
95% CI |
1 |
86 |
82 |
4 |
92 |
89 |
2 |
95 |
93 |
5 |
84 |
80 |
3 |
89 |
85 |
6 |
83 |
79 |
Three additional readers in each study read XRM alone. For these readers over both studies, sensitivity ranged from 68%
to 73% and specificity in non-malignant breasts ranged from 86% to 94%.
In breasts with malignancy, a false positive detection rate was calculated as the percentage of subjects for which the
readers assessed a region as malignant which could not be verified by SoT. The false positive detection rates for Gadavist
BMR ranged from 39% to 53% (95% CI Upper Bounds ranged from 44% to 58%).
MRA
Patients with known or suspected disease of the supra-aortic arteries (for evaluation up to but excluding the basilar artery)
were enrolled in Study C, and patients with known or suspected disease of the renal arteries were enrolled in Study D. In
both studies, non-contrast, 2D time-of-flight (ToF) magnetic resonance angiography (MRA) was performed prior to
Gadavist MRA using a single intravenous injection of 0.1 mmol/kg. The injection rate of 1.5 mL/second was selected to
extend the injection duration to at least half of the imaging duration. Imaging was performed with parallel-channel, 1.5T
MRI devices and an automatic bolus tracking technique to trigger the image acquisition following Gadavist administration
using elliptically encoded, T1-weighted, 3D gradient-echo image acquisition and single breath hold. Three central readers
blinded to clinical information interpreted the ToF and Gadavist MRA images. Three additional central readers interpreted
separately acquired computed tomographic angiography (CTA) images, which were used as the standard of reference
(SoR) in each study.
The studies included 749 subjects: 457 were evaluated in Study C, with an average age of 68 (range 25–93); 64% were
male; 80% white, 28% black, and 16% Asian. An additional 292 subjects were evaluated in Study D, with an average age
of 55 (range 18–88); 54% were male; 68% white, 7% black, and 22% Asian.
Efficacy was evaluated based on anatomical visualization and performance for distinguishing between normal and
abnormal anatomy. The visualization metric depended on whether readers selected, “Yes, it can be visualized along its
entire length...” when responding to the question, “Is this segment assessable?” Twenty-one segments in Study C and six
segments in Study D were presented per subject to each reader. The performance metrics, sensitivity and specificity,
depended on digital caliper-based quantitation of arterial narrowing in visualized, non-occluded, abnormal-appearing
segments. Significant stenosis was defined as at least 70% in Study C and 50% in Study D. Performance of Gadavist
MRA compared to ToF MRA was calculated using an imputation method for non-visualized segments by assigning them
as a 50% match with SoR and a 50% mismatch. Performance of Gadavist MRA compared to a pre-specified threshold of
50% was calculated after excluding non-visualized segments. Measurement variability and visualization of accessory
renal arteries was also evaluated.
Results were analyzed for each of the three central readers.
Table 10: Visualization, Sensitivity, Specificity
STUDY C: SUPRA-AORTIC ARTERIES (457 patients)
Performance at the segment level
95971 segments of which 1581 were positive for stenosis by SoR2 |
|
VISUALIZATION (%) |
SENSITIVITY (%) |
SPECIFICITY (%) |
READER |
GAD
MRA |
ToF
MRA |
GAD − ToF
(CI3) |
GAD
MRA |
ToF
MRA |
GAD − ToF
(CI4) |
GAD
MRA |
ToF
MRA |
GAD − ToF
(CI4) |
1 |
88 |
24 |
64
(61, 67) |
60 |
54 |
6
(-4, 14) |
92 |
62 |
30
(29, 32) |
2 |
95 |
75 |
20
(18, 21) |
60 |
54 |
6
(-3, 14) |
95 |
85 |
10
(9, 11) |
3 |
97 |
82 |
15
(13, 17) |
58 |
55 |
3
(-4, 11) |
97 |
89 |
8
(7, 9) |
STUDY D: RENAL ARTERIES (292 patients)
Performance at the segment level
17521 segments of which 1331 were positive for stenosis by SoR2 |
4 |
98 |
82 |
16
(13, 20) |
52 |
51 |
1(-9, 11) |
94 |
83 |
11
(9, 14) |
5 |
96 |
72 |
24
(21, 28) |
54 |
39 |
15
(6, 24) |
95 |
85 |
10
(8, 12) |
6 |
96 |
78 |
17
(14, 21) |
53 |
50 |
3
(-6, 12) |
94 |
81 |
13
(11, 16) |
1Number of segments varied between readers; number for majority-reader shown.
2Standard of Reference based on aggregate interpretation of three central CTA readers.
395.1/95% (Study C/D) confidence interval for two-sided comparison.
490.1/90% (Study C/D) confidence interval for one-sided comparison against non-inferiority margin of -7.5. |
GAD MRA = Post-contrast Gadavist Magnetic Resonance Angiography, ToF = Non-contrast 2D-Time of Flight.
For all three supra-aortic artery readers in Study C, the lower bound of confidence for the sensitivity of Gadavist MRA did
not exceed 54%. For all three renal artery readers in Study D, the lower bound of confidence for the sensitivity of
Gadavist MRA did not exceed 46%.
Measurement Variability
For both MRA and CTA, readers varied in the quantity of narrowing they assigned to the same arterial segments. Table 11
shows the percentage of patients in whom the measurement range was 30% or greater for the left or right internal carotid
and proximal renal artery segments. There were approximately four measurements per patient segment, one from the site
and three central readers. Measurement variability was high for both CTA and MRA, but numerically lower for Gadavist
compared to non-contrast ToF MRA.
Table 11: Percent of Patients with Range ≥ 30%, ≥ 50%, ≥ 70% for Measurement of
Stenoses and Normal Vessel Diameters
|
Internal Carotid |
Proximal Main Renal |
N |
≥ 30% |
≥ 50% |
≥ 70% |
N |
≥ 30% |
≥ 50% |
≥ 70% |
CTA |
456 |
40 |
11 |
4 |
292 |
59 |
33 |
9 |
ToF MRA |
443 |
55 |
22 |
9 |
270 |
44 |
22 |
9 |
Gadavist MRA |
454 |
47 |
13 |
4 |
286 |
34 |
14 |
4 |
Visualization Of Accessory Renal Arteries For Surgical Planning And Renal Donor Evaluation (Study D Only)
Of 1752 main arteries visualized by the central CTA readers, 266 (15%) were also associated with positive visualization
of at least one accessory (duplicate) artery. With the central MRA readers, the comparable rates were 232 of 1752 (13%)
for Gadavist MRA compared to 53 of 1752 (3%) for ToF MRA.
Cardiac MRI
Two studies similar in design, Study E and Study F, evaluated the sensitivity and specificity of Gadavist cardiac MRI
(CMRI) for detection of coronary artery disease (CAD) in adult patients with known or suspected CAD. Patients were
excluded from study if they had a history of coronary artery bypass grafting, or if it was known in advance that they were
unable to hold their breath, or had atrial fibrillation or other arrhythmia likely to prevent electrocardiogram-gated CMRI.
The studies were multi-center, open-label, and evaluated 764 subjects for efficacy: 376 in Study E, with an average age of
59 (range 20–84); 69% male; 74% white, 1% black, and 25% Asian; and 388 subjects in Study F, with an average age of
59 (range 23–82); 61% male; 67% white, 17% black, and 12% Asian.
All subjects underwent dynamic first-pass Gadavist imaging during vasodilator stress, followed ~10 minutes later by
dynamic first-pass Gadavist imaging at rest, followed ~5 minutes later with imaging during a period of gradual Gadavist
washout from the myocardium (late gadolinium enhancement, LGE). Imaging was performed on 1.5 T or 3.0 T MRI
devices equipped with multichannel surface coils to support accelerated acquisitions with parallel imaging, T1-weighted,
2D gradient-echo, dynamic acquisition of perfusion with at least 3 slices per heartbeat. Gadavist was administered
intravenously at a rate of ~4 mL/second as two separate bolus injections (0.05 mmol/kg each), the first at peak
pharmacologic stress (~3 minutes after start of ongoing adenosine infusion, or immediately after completion of
regadenoson administration, at approved doses). No additional Gadavist was administered for LGE imaging.
Images were read by three independent readers blinded to clinical information. Reader detection of CAD depended on
visually detecting defective perfusion or scar on Gadavist CMRI (stress, rest, LGE) imaging. Quantitative coronary
angiography (QCA) was used to measure intraluminal narrowing and served as the standard of reference (SoR).
Computed tomographic angiography (CTA) was used as the SoR if disease could be unequivocally excluded, and no
coronary angiography (CA) was available. The left ventricular myocardium was divided into six regions. Readers
provided per-region (CMRI, CTA) and per-artery (QCA) interpretations for each subject. Subject-level endpoints
reflected each subject’s most abnormal localized finding.
The sensitivity results for Gadavist CMRI to detect CAD defined as either maximum stenosis ≥ 50% or ≥ 70% by QCA
are presented in Table 12. For each reader, sensitivity of Gadavist CMRI larger than 60% can be concluded if the lower
95% confidence limit of the sensitivity estimate exceeds the pre-specified threshold of 60%.
Table 12: Sensitivity (%) of Gadavist-CMRI for Detection of CAD in Patients with Maximum Stenosis*
of ≥ 50% and ≥ 70%
|
Study E |
Study F |
≥ 50%
N=141 |
≥ 70%
N=108 |
≥ 50%
N=150 |
≥ 70%
N=105 |
Reader 1** |
77 (69, 83) |
90 (83, 95) |
65 (57, 72) |
77 (68, 85) |
Reader 2** |
65 (57, 73) |
80 (71, 87) |
56 (48, 64) |
71 (62, 80) |
Reader 3** |
65 (56, 72) |
79 (70, 86) |
61 (53, 69) |
76 (67, 84) |
* Stenosis determined by Quantitative Coronary Angiography (QCA)
** CMRI images were assessed by six independent blinded readers, three in each study.
*** The bolded value represents the lower limit of the 95% confidence interval, which is compared to a pre-specified threshold of 60% for evaluation of sensitivity. |
The specificity results for Gadavist CMRI to detect CAD defined as either maximum stenosis ≥ 50% or ≥ 70% by QCA
are presented in Table 13. For each reader, specificity of Gadavist CMRI larger than 55% can be concluded if the lower
95% confidence limit of the specificity estimate exceeds the pre-specified threshold of 55%.
Table 13: Specificity (%) of Gadavist CMRI for Exclusion of CAD in Patients with Maximum Stenosis*
of ≥ 50% and ≥ 70%
|
Study E |
Study F |
≥ 50%
N=235 |
≥ 70%
N=268 |
≥ 50%
N=238 |
≥ 70%
N=283 |
Reader 1** |
85 (80, 89)*** |
83 (78, 87) |
85 (80, 90) |
82 (77, 86) |
Reader 2** |
92 (88, 95) |
91 (87, 94) |
89 (84, 92) |
87 (83, 91) |
Reader 3** |
92 (88, 95) |
91 (87, 94) |
90 (85, 93) |
87 (82, 91) |
* Stenosis determined by Quantitative Coronary Angiography (QCA)
** CMRI images were assessed by six independent blinded readers, three in each study.
*** The bolded value represents the lower limit of the 95% confidence interval, which is compared to a pre-specified threshold of 55% for evaluation of specificity. |
In Study E, among the 33 patients with maximum stenosis by QCA between 50% and <70%, the proportion of Gadavist-
CMRI positive detections of CAD ranged from 15% to 33% . In Study F, among the 45 patients with maximum stenosis
by QCA between 50% and < 70%, the proportion of Gadavist-CMRI positive detections of CAD ranged from 20% to
35%. The results of Gadavist-CMRI reads to detect CAD in patients with maximum stenosis between 50% and < 70% are
summarized in Table 14.
Table 14: Gadavist-CMRI Detection of CAD in Patients with Maximum Stenosis* between 50% and <
70%
|
Study E (n=33) |
Study F (n=45) |
Reader 1** |
11 (33%) |
16 (35%) |
Reader 2** |
5(15%) |
9 (20%) |
Reader 3** |
6(18%) |
12 (26%) |
* Stenosis determined by Quantitative Coronary Angiography (QCA).
**CMRI images were assessed by six independent blinded readers, three in each study. |
Left Mainstem Stenosis (LMS)
The studies did not include sufficient numbers of subjects to characterize the performance of Gadavist CMRI for detection
of LMS, a subgroup at high risk from false negative reads. In Studies E and F, only three subjects had isolated LMS
stenosis >50%. In two of the three cases, the CMRI was interpreted as normal by at least two of the three readers (false
negative). Sixteen subjects had LMS stenosis >50% (including subjects with isolated LMS stenosis and subjects with
LMS stenosis in addition to stenoses elsewhere). . In five of these sixteen cases, the CMR was interpreted as normal by at
least two of the three readers (false negative).