High dose rate intracoronary radiation for inhibition of neointimal formation in the stented and balloon-injured porcine models of restenosis: Angiographic, morphometric, and histopathologic analyses

Mazur, Wojciech; Ali, M. Nadir; Khan, Myrna M.; Dabaghi, Salim F.; DeFelice, Clement A.; Paradis, Pierre; Butler, E. Brian; Wright, Ann E.; Fajardo, Luis F.; French, Brent A.; Raizner, Albert E.

doi:10.1016/s0360-3016(96)00298-2

Cited by 123 publications

(42 citation statements)

References 22 publications

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“…It has been demonstrated in animal models [3][4][5][6][7] and more recently in clinical studies that intracoronary irradiation significantly reduces restenosis, presumably by inhibiting smooth muscle cell proliferation and neointima formation. Irradiation of human femoral arteries appears to confirm these findings.…”

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confidence: 99%

Intracoronary Radiation for Prevention of Restenosis

1998

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Background-Intravascular irradiation with ␤-emitters has been proposed for inhibition of restenosis in coronary arteries after balloon angioplasty or stent implantation. Previous studies have shown the effectiveness of ␥-radiation to prevent recurrent restenosis, even in the presence of an implanted stent. The limited range of ␤-particles compared with ␥-radiation, however, opens the question of whether absorption and scattering of ␤-particles by stent struts will cause significant perturbations in the uniformity and magnitude of the radiation dose, which may in turn compromise treatment. Methods and Results-Nine different stents were deployed with a balloon filled with a ␤-emitting radioactive liquid. Dose distributions were measured with Gafchromic film. Stents varied significantly in their absorption of ␤-particles. Some stents, constructed of fine meshed wires, produced minimal dose perturbations. Others, with thicker, high-atomicnumber struts, induced cold spots in the dose distribution adjacent to the wires of Յ35%. Average dose reduction varied from 4% to 14% in the presence of various stents. Conclusions-Radiation strategy may have to be tailored to stent design. Stents that minimally perturb the dose distribution may be deployed before irradiation. Those that significantly alter the radiation dose might be better deployed after irradiation. Dose prescriptions may require modification if such perturbations prove clinically significant. Observed dose perturbations, however, decreased rapidly with increasing distance from the stent, which may mitigate the clinical impact of these findings. This, as well as the effects of stents on ␥-dose distributions, requires further investigation.

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confidence: 99%

Intracoronary Radiation for Prevention of Restenosis

1998

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“…The prescribed dose positively correlated with inhibition of neointimal proliferation in animal studies 6,7 and in human pilot trials. 8,9 As a result, current dose-prescription protocols were organized in reference to these initial studies.…”

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Delivered Dose and Vascular Response After β-Radiation for In-Stent Restenosis

et al. 2002

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Background-Observations from previous intracoronary radiation therapy trials noted a considerable discrepancy between the prescribed radiation dose and the dose actually delivered. The aims of this study were to investigate the effect of actual delivered dose on vascular changes and to test the appropriateness of the current dose prescription. Methods and Results-Serial volumetric intravascular ultrasound (IVUS) analysis was performed in 30 in-stent restenosis cases treated with a 40-mm 90 Sr/Y source train. The fixed dose was prescribed at 2 mm from the centerline of the source train (18.4 Gy at 2 mm for reference diameter Յ3.35 mm and 23 Gy for diameter Ն3.36 mm). Only stent segments with full radiation coverage and device injury were enrolled and divided into 2-mm-long subsegments (nϭ202). D S90 EEM (the minimum dose absorbed by 90% of the external elastic membrane surface) was calculated as the delivered dose corresponding to each segment, assuming that the radiation catheter occupied the same position in the vessel as the IVUS catheter. Mean D S90 EEM of 23.5Ϯ5.82 Gy (range 12.3 to 41.7 Gy) was delivered to these subsegments. Overall, intimal hyperplasia volume remained constant from postintervention to follow-up (2.23Ϯ1.10 to 2.32Ϯ1.09 mm 3 /m; PϭNS). Regression analysis revealed there was no correlation between delivered dose intensity and changes in intimal hyperplasia volume. No particular dose-dependent complications were appreciated in this delivered dose range. Conclusions-The current dose-prescription protocol of 90 Sr/Y radiation to native in-stent restenosis lesions may provide substantial inhibition of neointimal reproliferation regardless of the actual delivered dose intensity.

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“…Mazur, et al found that 10-25 Gy of 192 Ir using a high dose-rate afterloader inhibited the 4-week post-injury intimal thickening in left coronary arteries treated by balloon angioplasty but had no effect on the stented right coronary artery. 98) Wiedermann, et al also reported that neointima from aggressive oversize stenting did not respond to radiation therapy. The mixed results of these preliminary studies may be due either to the differences in doses or dose rates, variance in the healing response to stent injury, or some combination of these factors.…”

Section: Clinical Trials Using Gamma-irradiation (Table Ii)mentioning

confidence: 99%

<b>Irradiation and Postangioplasty Restenosis</b>

et al. 2000

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SUMMARYOne of the most intriguing developments in recent years towards prevention of restenosis after angioplasty is the use of ionizing radiation. The background for the use of radiation treatment for this application is sound, since radiation is used not only to treat malignant cancerous growths but also is used for treatment of benign hyperplastic disorders such as post-surgical keloid formation and recurrence of pterygium after surgical removal. Restenosis can be considered a form of overexuberant wound healing triggered by angioplasty. Ionizing radiation inhibits serum-stimulated proliferation of many cell types including fibroblasts and smooth muscle cells in vitro and also suppresses the synthesis of collagen by cultured fibroblasts. Liermann who showed inhibition of post-stent restenosis first used ionizing radiation for restenosis prevention clinically in iliac and iliofemoral arteries. Subsequently, extensive animal studies in various restenosis models have shown a profound inhibitory effect of catheter-based radiation (endovascular brachytherapy) on neointima formation and overall vessel shrinkage (negative remodeling). 1) performed the first coronary balloon angioplasty. After more than 20 years, percutaneous transluminal coronary angioplasty (PTCA) is now widely accepted as an effective therapy for selected patients with symptomatic coronary artery disease. However, the over-compensatory wound healing response to angioplasty causing restenosis significantly limits the long-

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High dose rate intracoronary radiation for inhibition of neointimal formation in the stented and balloon-injured porcine models of restenosis: Angiographic, morphometric, and histopathologic analyses

Cited by 123 publications

References 22 publications

Intracoronary Radiation for Prevention of Restenosis

Intracoronary Radiation for Prevention of Restenosis

Delivered Dose and Vascular Response After β-Radiation for In-Stent Restenosis

<b>Irradiation and Postangioplasty Restenosis</b>

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