32P Brachytherapy in the Treatment of Complex Cypher In-Stent Restenosis

Comparison of drug-eluting stents and drug-coated balloon for the treatment of drug-eluting coronary stent restenosis: A randomized RESTORE trial

BACKGROUND

This study sought to evaluate the optimal treatment for in-stent restenosis (ISR) of drug-eluting stents (DESs).

METHODS

This is a prospective, multicenter, open-label, randomized study comparing the use of drug-eluting balloon (DEB) versus second-generation everolimus-eluting stent for the treatment of DES ISR. The primary end point was in-segment late loss at 9-month routine angiographic follow-up.

RESULTS

A total of 172 patients were enrolled, and 74 (43.0%) patients underwent the angiographic follow-up. The primary end point was not different between the 2 treatment groups (DEB group 0.15±0.49 mm vs DES group 0.19±0.41 mm, P=.54). The secondary end points of in-segment minimal luminal diameter (MLD) (1.80±0.69 mm vs 2.09±0.46 mm, P=.03), in-stent MLD (1.90±0.71 mm vs 2.29±0.48 mm, P=.005), in-segment percent diameter stenosis (34%±21% vs 26%±15%, P=.05), and in-stent percent diameter stenosis (33%±21% vs 21%±15%, P=.002) were more favorable in the DES group. The composite of death, myocardial infarction, or target lesion revascularization at 1 year was comparable between the 2 groups (DEB group 7.0% vs DES group 4.7%, P=.51).

CONCLUSIONS

Treatment of DES ISR using DEB or second-generation DES did not differ in terms of late loss at 9-month angiographic follow-up, whereas DES showed better angiographic results regarding minimal MLD and percent diameter stenosis. Both treatment strategies were safe and effective up to 1year after the procedure.

Verification and uniformity control of doses for Sr/Y intravascular brachytherapy sources using radiochromic film dosimetry

Intravascular brachytherapy (IVBT) is a useful treatment modality for the recurrence of in-stent restenosis following drug-eluting stents (DES) or IVBT failure. The objective of this study was to measure the dose rate of (90)Sr/(90)Y IVBT sources for comparison with that given by the manufacturer and to control the dose uniformities of these sources along the source axis. The dose rates of (90)Sr/(90)Y beta sources were measured with a radiochromic film in a custom-made phantom. The films for calibration were irradiated using (60)Co photon beams. The results for the three sources were 4.5%, 2.3%, and 3.5% higher than the corresponding certificate values. Maximum and minimum of the dose rates varied within +/-10% of those at source center; and maximum dose discrepancy for the first (90)Sr/(90)Y source train was 8.2%; for the second source train, 7.1%; and for the third source train, 5.1%. Our study showed that the dose rates given by the manufacturer for the three (90)Sr/(90)Y IVBT sources were reliable and dose uniformities were within +/-10% along two thirds of the treatment length.

Combining sirolimus-eluting stents and external irradiation in cholesterol-fed rabbits increased incomplete stent apposition and decreased re-endothelialization

Restenosis after the implantation of a drug-eluting stent or after vascular irradiation therapy shares similar physiopathological mechanisms. No experimental data are currently available on vascular wall behavior after external irradiation on arteries stented with sirolimus-eluting stents (SES). Ten New Zealand white rabbits received a 0.5% cholesterol-enriched chow for 1 month. Bilateral iliac artery stent implantation was then performed with an SES (Cypher; Cordis Corp). The animals were randomized into either an irradiated group (I, 2 Gy external x-ray irradiation, n = 5) or a control group (C, n = 5). The cholesterol-enriched chow was continued for 1 additional month after stent implantation. The stented arteries were harvested for histological analyses. The number and the percentage of incompletely apposed stents struts (IASS) were significantly higher in irradiated versus control group (3.05 +/- 0.46 vs. 1.57 +/- 0.27 IASS, P < 0.01, and 28.44% +/- 3.97% vs. 15.2% +/- 2.46% of IASS, P < 0.01, respectively). The mean neointimal thickness behind the IASS was also higher in the irradiated group (I: 28.3 +/- 2.5 microm vs. C: 18.2 +/- 2.3 microm, P < 0.01). Re-endothelialization was lower in irradiated group (I: 44.6% +/- 17.5% vs. C: 75.2% +/- 5.7%, P < 0.01). The present study revealed that low-dose external irradiation increased incomplete stent apposition and reduced re-endothelialization of SES. These results underscore the potential deleterious cumulative side effects of these 2 procedures to prevent restenosis.

The use of gel dosimetry to measure the 3D dose distribution of a 90Sr/90Y intravascular brachytherapy seed

Absorbed dose distributions in 3D imparted by a single (90)Sr/(90)Y beta particle seed source of the type used for intravascular brachytherapy were investigated. A polymer gel dosimetry medium was used as a dosemeter and phantom, while a special high-resolution laser CT scanner with a spatial resolution of 100 microm in all dimensions was used to quantify the data. We have measured the radial dose function, g(L)(r), observing that g(L)(r) increases to a maximum value and then decreases as the distance from the seed increases. This is in good agreement with previous data obtained with radiochromic film and thermoluminescent dosemeters (TLDs), even if the TLDs underestimate the dose at distances very close to the seed. Contrary to the measurements, g(L)(r) calculated through Monte Carlo simulations and reported previously steadily decreases without a local maximum as a function of the distance from the seed. At distances less than 1.5 mm, differences of more than 20% are observed between the measurements and the Monte Carlo calculations. This difference could be due to a possible underestimation of the energy absorbed into the seed core and encapsulation in the Monte Carlo simulation, as a consequence of the unknown precise chemical composition of the core and its respective density for this seed. The results suggest that g(L)(r) can be measured very close to the seed with a relative uncertainty of about 1% to 2%. The dose distribution is isotropic only at distances greater than or equal to 2 mm from the seed and is almost symmetric, independent of the depth. This study indicates that polymer gel coupled with the special small format laser CT scanner are valid and accurate methods for measuring the dose distribution at distances close to an intravascular brachytherapy seed.

Comparison with conventional therapies of repeated sirolimus-eluting stent implantation for the treatment of drug-eluting coronary stent restenosis

This study compared the safety and efficacy of repeat percutaneous coronary intervention (PCI) using sirolimus-eluting stents (SESs) with conventional therapies for restenosis after drug-eluting stent placement. Fifty-five consecutive patients with 58 restenotic lesions (31 treated with SESs and 27 treated with paclitaxel-eluting stents) underwent PCI using SESs (33 lesions) or conventional therapies comprising cutting balloon angioplasty alone (11 lesions) or intracoronary brachytherapy (14 lesions). Baseline characteristics were similar for the 2 groups, except for greater edge involvement (75.8% vs 36.0%, p = 0.002) and less stent expansion (0.74 +/- 0.17 vs 0.95 +/- 0.21, p = 0.006) in the SES group than in the conventional group. The SES group achieved a greater postprocedural luminal gain than the conventional group (1.98 +/- 0.50 vs 1.22 +/- 0.48 mm, p <0.001). Follow-up angiography showed that late luminal loss (0.27 +/- 0.56 vs 0.76 +/- 0.84 mm, p = 0.021) and recurrent angiographic restenosis rate (3.6% vs 35.0%, p = 0.006) were lower in the SES group than in the conventional group. The repeated target lesion revascularization-free survival rates at 1 year were 96.7 +/- 3.2% for the SES group and 91.7 +/- 5.6% for the conventional group (p = 0.399). In conclusion, use of SESs was associated with a lower recurrent restenosis rate compared with conventional therapies.

Repeat intracoronary beta-brachytherapy using a rhenium-188-filled balloon catheter for recurrent restenosis in patients who failed intracoronary radiation therapy

BACKGROUND

Conventional percutaneous coronary intervention (PCI) in restenotic lesions after brachytherapy failure is associated with a high recurrence rate of restenoses and revascularizations. Intracoronary brachytherapy using a liquid rhenium-188-filled balloon in de novo or restenotic lesions safely and effectively reduced restenosis rates. We report clinical and angiographic data regarding the safety and efficacy of rhenium-188 brachytherapy in restenoses after brachytherapy failure.

METHODS

Fourteen patients with restenosis after brachytherapy failure received rhenium-188 beta-brachytherapy. Follow-up was performed angiographically after 6 months and clinically after 12 months. Primary clinical endpoint was the incidence of major adverse cardiac events (MACE) defined as any death, myocardial infarction or repeat revascularization in the target vessel within 12 months. Secondary angiographic endpoints were the binary restenosis rate and late loss in the total segment including edge effects at 6 months.

RESULTS

The prescribed dose of 22.5 Gy (n=12) or 30 Gy (n=2) was successfully delivered in all patients. In two lesions, a bare-metal stent was implanted. The mean length of the irradiated segment was 40.0+/-15.7 mm. The mean diameter of the irradiation balloon was 2.96+/-0.37 mm. Angiographic follow-up was done in 13 of 14 patients. There was no edge stenosis or coronary aneurysm. Within the total segment, late loss was 0.39+/-0.64 mm and late loss index was 0.18+/-0.40 with a binary restenosis rate of 23%. Twelve months' clinical follow-up was available in all patients, which showed a MACE rate of 7% due to one target lesion revascularization (TLR).

CONCLUSIONS

Intracoronary beta-brachytherapy with a liquid rhenium-188-filled balloon in restenoses after intracoronary radiation therapy failure including 12 months combined antiplatelet therapy is safe with respect to vessel thrombosis, late coronary occlusion or aneurysm formation. With limited use of stenting, angiographic and clinical follow-up for repeat brachytherapy were favorable and it is associated with low restenosis and target vessel revascularization rate.

Intracoronary radiation therapy for multi-drug resistant in-stent restenosis: Initial clinical experience

While randomized clinical trials have demonstrated the excellent efficacy of sirolimus-eluting stents (SES) for de novo lesions, the optimal treatment for SES-restenosis is not known. Management may include stand-alone balloon angioplasty, repeat SES implantation, or placement of a drug-eluting stent (DES) with an alternative antiproliferative agent (i.e., a paclitaxel-eluting stent, PES). The appropriate management strategy for recurrent restenosis after PES implantation for SES restenosis is even less clear. We report the initial clinical experience with intracoronary radiation therapy (ICRT) for multi-DES resistant restenosis. We performed ICRT in five patients with recurrent restenosis after treatment with both SES and PES. Over a median follow-up of 256 days (range 75-489 days), one patient had a target lesion revascularization at 182 days and subsequently died at 483 days following the procedure. Our findings support the further study of this management approach.