Radiation for restenosis: the dark side of arteries Robert S Schwartz MD Professor of Medicine Mayo Clinic Rochester, MN
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Radiation for restenosis:the dark side of arteries
Robert S Schwartz MDProfessor of MedicineMayo ClinicRochester, MN
Stimulation of neointima within an irradiated artery
Figure 1
Minimal neointimal neoplasia post stent placement
Figure 2
External beam radiation
• major US center• 11 patient pilot study• 8 Gy external beam radiation• 11/11 restenosis
the restenosis rate was 100%
Radiation injury to blood vessels
• capillary injury is greatest• obliteration of capillaries
one mechanism of anti-tumor action• thrombosis, rupture, fibrosis• occasionally lymphocytic vasculitis• venous lesions are uncommon
Induction of neointima post external beam radiation
Figure 3
Venezuelan study
the late loss is too high
Figure 4: late loss (millimeters)
0.44 0.400.33 0.32 0.28 0.27 0.26 0.25
Condado LRT MARCATOR BENESTENT HELVETICA CARPORT MERCATOR PARK
Condado J, Circulation 1997;96:727
3 questions on radiation
• Q: Is arterial radiation feasible?A: “Yes”
• Q: Is it safe?A: “We doubt it”
• Q: Is it efficacious?A:”We don’t think so”
Serruys et al, Circulation 1997;96:709-712
Neointimal hyperplasia at former sites of radiation
Figure 5
PREVENT trial
Figure 6Restenosis in the treated segment
Raizner et al, PREVENT trial 1998
9.1%
22.2%
0.0%
25.0%
P 32 Control
PREVENT trial
Figure 7Restenosis in the adjacent segment
Raizner et al, PREVENT trial 1998
22.7%
11.1%
0.0%
25.0%
P 32 Control
PREVENT trial
Figure 8Restenosis in the treated and adjacent segments
Raizner et al, PREVENT trial 1998
22.7% 22.2%
0.0%
25.0%
P 32 Control
BERT trial
• restenosis rate of 17%• 6 patients with an “edge problem”
• overall restenosis rate of 25%
Beta emitting stents and restenosis
Figure 9Restenosis in the treated and adjacent segments
56.0%(10/18)
39.0%(11/28)
45.0%(5/11)
50.0%(1/2)
0.75-3 uCi 3-6 uCi 6-12 uCi 12-20 uCi
Cellular neointimal hyperplasia of in-stent restenosis
Figure 10
Neointimal hyperplasia at former sites of radiation
Figure 11
• European registry, 150 patients• PTCA up to 2 vessels• Beta-Cath system, 90-Sr/Y• 12,14,16 Gy to 2 mm from source• target vessel restenosis 30%• late loss index 13%
Serruys, 1999
The BRIE trial
Human coronary artery thrombus in situ
Figure 12
Multi-layered thrombus in a pig coronary artery
Figure 13
Old thrombus
New thrombus
Absence of neointima
Intracoronary beta radiation
Figure 14Effects of intracoronary beta-radiation after 6 months in stented vessels
2.843.16
0
1
2
3
4
control treated
Neoin
tim
al
are
a (
mm
2)
P=NS
Figure 15Angiographic restenosis rate
54%
17%
control radiated
SCRIPPS trial
Figure 16The SCRIPPS radiated group, a long term analysis
0
1
2
3
post 6 months 3 years
Min
imu
m l
um
inal
dia
mete
r (m
m)
ControlRadiated
SCRIPPS trial
P=NS
Figure 17GAMMA-I 6 month follow-up
0
1
2
3
before pre post f/u
Min
imu
m l
um
inal
dia
mete
r (m
m)
ControlRadiated
GAMMA-I in-stent measures
EVG Actin
Heat injury
Figure 18
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