Clinical and angiographic outcomes after use of 90Strontium/90Yttrium beta radiation for the treatment of in-stent restenosis: results from the Stents and Radiation Therapy 40 (START 40) registry

The Ongoing Saga of the Evolution of Percutaneous Coronary Intervention: From Balloon Angioplasty to Recent Innovations to Future Prospects

The advances in percutaneous coronary intervention (PCI) have been, above all, dependent on the work of pioneers in surgery, radiology, and interventional cardiology. From Grüntzig's first balloon angioplasty, PCI has expanded through technology development, improved protocols, and dissemination of best-practice techniques. We can nowadays treat more complex lesions in higher-risk patients with favourable results. Guide wires, balloon types and profiles, debulking techniques such as atherectomy or lithotripsy, stents, and scaffolds all represent evolutions that have allowed us to tackle complex lesions such as an unprotected left main coronary artery, complex bifurcations, or chronic total occlusions. Best-practice PCI, including physiology assessment, imaging, and optimal lesion preparation are now the gold standard when performing PCI for sound indications, and new technologies such as intravascular lithotripsy for lesion preparation, or artificial intelligence, are innovations in the steps of 4 decades of pioneers to improve patient care in interventional cardiology. In the present review, major innovations in PCI since the first balloon angioplasty and also uncertainties and obstacles inherent to such medical advances are described.

Coronary intravascular brachytherapy for in-stent restenosis: A review of the contemporary literature

Intracoronary stent restenosis (ISR) is a clinically relevant challenge in the modern era. Heterogeneity in patient- and lesion-specific factors can further compound this clinical challenge. Coronary intravascular brachytherapy (IVBT) was the standard therapeutic approach for ISR prior to the advent of drug-eluting stents (DES). Despite prospective data describing the superiority of DES over IVBT for treating de novo ISR, IVBT remains a treatment option for patients with complex disease. The purpose of this review is to evaluate the historical and contemporary literature surrounding IVBT in order to elucidate its role in modern cardiac care and to describe opportunities for future investigations to improve patient selection. Herein, we provide a review of the contemporary literature describing IVBT as a safe and effective treatment option for patients with recurrent, refractory ISR after multilayer DES and no good surgical or mechanical option. Combination therapy with emerging technologies such as DCBs may further increase efficacy.

The birth, decline, and contemporary re-emergence of endovascular brachytherapy for prevention of in-stent restenosis

Despite the advent of drug-eluting stents and dual antiplatelet therapy in the interventional management of cardiovascular disease, restenosis rates remain high with significant sequelae. Endovascular brachytherapy-popular in the 1990s and early 2000s-has recently resurfaced as a cost-effective treatment option. In this work, we outline the history of endovascular brachytherapy starting with its earliest promise in the 1990s. We discuss the development of drug-eluting stents and dual antiplatelet strategies and their impact on the perceived benefit of endovascular brachytherapy. For the contemporary era, we propose novel roles for endovascular brachytherapy in complex coronary artery disease and in high-risk patients managed with drug-eluting stents. We discuss the impetus for reducing the requirement and duration of dual antiplatelet therapy using endovascular brachytherapy. We also review innovative opportunities for endovascular brachytherapy after bare-metal stent placement in both coronary and noncoronary territories and offer economic arguments in favor of endovascular brachytherapy. Trials of endovascular brachytherapy in these regimes are merited.

In-stent restenosis

The introduction of coronary stents marked a major turning point in the practice of interventional cardiology. Whereas the efficacy of balloon angioplasty was challenged both by immediate mechanical complications and by a high incidence of restenosis, coronary stents offered cardiologists a means by which to not only augment immediate procedural success, but also to reduce the incidence of restenosis following coronary intervention. However, despite technological advances and an improved understanding of the restenotic process, the overall rate of in-stent restenosis following bare metal stent implantation remains high. Although the introduction of drug-eluting stents has further reduced the incidence of restenosis, the "real-world" application of drug-eluting stents in increasingly complex lesion and patient subsets has given way to the even greater clinical challenge of managing drug-eluting stent restenosis. Although the standard treatment of bare metal stent restenosis typically involves placement of a drug-eluting stent, the optimal therapeutic approach to drug-eluting stent restenosis remains less defined. The issue of in-stent restenosis (especially following implantation of a drug-eluting stent) remains a clinical challenge, and investigation into therapeutic options remains ongoing. As technology evolves, such investigation will likely incorporate novel approaches including drug-coated balloons novel stent designs.

Predictors of recurrent in-stent restenosis after beta-radiation: An analysis from the START 40/20 trial

OBJECTIVE

The purpose of this study was to identify potential predictors, including clinical, procedural, angiographic, and intravascular ultrasound (IVUS) parameters, for recurrent in-stent restenosis (ISR) following beta-radiation 90Strontium/Yttrium (90Sr/Y) in a large multicenter trial.

BACKGROUND

Although adjunct brachytherapy reduces recurrent ISR after primary catheter-based intervention, recurrence of stenosis after brachytherapy still occurs.

METHODS

We analyzed 185 IVUS cohort patients in the STent And Restenosis Therapy (START) 40/20 trial where a 40-mm, 90Sr/Y, radioactive source train was exclusively used for treatment of ISR to be treatable with a 20-mm balloon.

RESULTS

Thirty-nine patients underwent target lesion revascularization. Preliminary univariate analysis showed that age, smoking, balloon/artery ratio, geographic miss, minimum lumen diameter, and diameter stenosis at baseline were associated with target lesion revascularization, while none of IVUS variables were (minimum lumen area, minimum stent area, or residual plaque burden). The multivariate logistic regression analysis showed that younger age, lower balloon/artery ratio, and presence of geographic miss were independent predictors of target lesion revascularization.

CONCLUSIONS

Even with adjunct beta-radiation therapy, initial mechanical optimization, such as appropriate balloon sizing and positioning, may be critical for the prevention of recurrent ISR.

Cutting Balloon: Review on Principles and Background of Use in Peripheral Arteries

This review describes peripheral use of cutting balloon (CB) angioplasty (CBA), its characteristics, and its distinction from conventional BA and describes the experimental and clinical background of its current use in peripheral arteries.

Evolution of vascular brachytherapy over time: Data from the RENO-registry analysis

OBJECTIVE

To study the evolution of procedural variations in vascular brachytherapy (VBT) and their relationship to medium-term outcome.

METHODS AND RESULTS

The RENO (European Surveillance Registry with Novoste Beta-Cath) prospectively collected procedural and clinical outcome data on 1098 patients treated with VBT. Patients were divided for this analysis into Group-I, the first 50% registered, and Group-II, the last 50% registered. Shorter 30-mm source trains were more commonly used in Group-I (p<0.001) while longer 40-mm (p=NS) and 60-mm (p<0.001) source trains were more commonly used in Group-II. Mean dwell time for radiation seeds was longer in Group-II compared to Group-I (4.20+/-1.48 min vs. 4.14+/-1.44 min; p<0.05). Mean radiation dose was higher in Group-II (19.73+/-3.33 Gy vs. 17.92+/-2.68 Gy; p<0.001). Cutting balloons were more frequently used in Group-II (p<0.001). There was significant drop in the incidence of geographic miss in Group-II (3.2% vs. 9%; p<0.00005). There were nonsignificant trends towards reduction in angiographic restenosis, target vessel (TV) revascularisation, death and major adverse cardiac events (MACE).

CONCLUSION

There has been a learning curve and evolution of VBT techniques over time. In general, there has been an increase in radiation source length, use of cutting balloons, dwell time and radiation dose. This has resulted in significant reduction of geographic miss and a trend towards improve clinical outcomes. Continued development may result in further improvement in the treatment of patients with in-stent restenosis (ISR).

Improving patient-specific dosimetry for intravascular brachytherapy

PURPOSE

Accurate patient-specific dosimetry in intravascular brachytherapy (IVBT) is generally difficult due to the extremely high-dose gradient, complexity of treatment device, and patient-specific geometry (e.g., calcification, stent, curvature, movement of target). The purpose of this study is to analyze quantitatively and systematically the dose effects of calcification, stent, guidewire, and source curvature on clinical dosimetry in an IVBT procedure, and propose a method that can be used to assess these effects in routine clinical practice.

METHODS AND MATERIALS

Monte Carlo techniques were used to calculate 3-D dose distribution in both homogeneous and inhomogeneous media for three most commonly used IVBT sources: (90)Sr beta (Novoste), (192)Ir gamma (Cordis/Best), and (32)P beta (Guidant). Dosimetric perturbations in the presence of metallic stents, calcified plaques, metallic guide wires, and source curvature were studied for situations commonly encountered in the clinic. The importance of each of these perturbations and their practical influence on patient-specific dosimetry were analyzed. Factors (plaque, stent, guidewire, and curvature) that may be used to correct/reduce these perturbations were introduced to prevent dosimetric cold spots during IVBT. Practical methods of using these correction factors are proposed.

RESULTS

Dose perturbations are significant due to the presence of source curvature, metallic stents, calcified plaques, and metallic guide wires, especially for beta sources. These perturbations can be as high as 30% under normal clinical conditions, although they can be much higher in extreme situations. Empirical relationships of plaque factor with the thickness of calcified plaque, stent factor with stent metallic surface area, guidewire with guidewire thickness, and curvature factor with the bending angle are derived. These relationships are found to be useful in improving clinical dose accuracy in IVBT treatment planning or dose evaluation after treatment.

CONCLUSIONS

Significant dose perturbations due to the presence of source curvature, metallic stents, calcified plaques, and guide wires have been found in IVBT for in-stent restenosis. Because it has been reported that, with the current prescriptions for IVBT, higher doses consistently improve treatment outcomes, the empirical method derived from this work can be used to assess cold spots dosimetrically, thus improving patient-specific dosimetry for IVBT.

Vascular brachytherapy in renal artery restenosis

PURPOSE OF REVIEW

As renal artery stenting becomes more commonly performed, the prevalence of renal artery in-stent restenosis will increase. Intracoronary brachytherapy is the only adjuvant therapy that has been shown to reduce the incidence of recurrent restenosis. This review addresses the mechanisms that make brachytherapy an effective tool for restenosis and its application to renal arteries.

RECENT FINDINGS

To date, the literature on renal artery brachytherapy for restenosis consists of several singular case reports and two case series. The first series of 13 patients had a 20% restenosis rate 1 year after brachytherapy, when Doppler ultrasound was used for follow-up monitoring. A report of a series of 5 patients, published this year, used surrogate markers for assessing efficacy as endpoints and found a similar restenosis rate.

SUMMARY

These series and case reports demonstrate that renal brachytherapy is feasible and safe. Comments on efficacy must await a randomized trial or accumulation of more anecdotal data.

[In 2003, what are the indications of brachytherapy in coronary arteries?]

Significant results obtained with coated stents in "de novo" coronary lesion treatment, particularly in complex lesions, have substituted brachytherapy indications. However, curitherapy results in diffuse or proliferative in-stent restenosis treatment show a significant reduction (30-50%) of restenosis and major adverse cardiac events. So, without sufficient scientific proofs with active stents in this indication, curitherapy is the only validated and authorized treatment of second diffuse or proliferative in-stent restenosis.

Successful reduction of in-stent restenosis in long lesions using beta-radiation--subanalysis from the RENO registry

PURPOSE

Long lesions remain a challenging task in interventional cardiology, with a high propensity of restenosis, especially within the stented segment. Although intracoronary gamma-radiation has been proved to reduce diffuse in-stent restenosis in long lesions, such an effect remains to be determined using beta-radiation.

METHODS AND MATERIALS

Of 1098 consecutive patients at 46 European centers treated with localized beta-radiation ((90)Sr, Novoste Beta-Cath System), 139 patients (mean age 61.5 +/- 10.7 years, 84% male, 22% with diabetes mellitus) with lesions treated using a >40-mm source length underwent radiation using a single 60-mm source train (34%) or a stepping/pullback procedure with a 30-mm (12%) or 40-mm (87%) source length after conventional interventional procedures. The mean lesion length was 35.3 +/- 17.9 mm.

RESULTS

Technical success was achieved in 96% of cases. Geographic miss was noted in 9 patients (6.5%). The reference (placebo) group was obtained from the Washington Hospital Center for In-Stent Restenosis Trial (WRIST) and the WRIST Trial for long lesions (LONG WRIST) studies by selecting the cases (94 patients) that required a dummy source length >/=13 seeds (or >51 mm in length). Statistically significant improvement was noted in late angiographic restenosis (34.7% vs. 76.5%, p <0.0001), target vessel revascularization (14.9% vs. 60.6), and major adverse cardiac events (i.e., death, myocardial infarction, or total vessel revascularization) (17.9% vs. 64.9%, p <0.0001) at 6 months in reference to the nonradiation group.

CONCLUSION

This subanalysis from the Radiation in Europe with Novoste study confirms the safety and efficacy of beta-radiation combined with conventional interventional procedures in patients with diffuse, long, in-stent restenosis

Use of water-equivalent plastic scintillator for intravascular brachytherapy dosimetry

Beta irradiation has recently been investigated as a possible technique for the prevention of restenosis in intravascular brachytherapy after balloon dilatation or stent implantation. Present methods of beta radiation dosimetry are primarily conducted using radiochromic film. These film dosimeters exhibit limited sensitivity and their characteristics differ from those of tissue, therefore the dose measurement readings require correction factors to be applied. In this work a novel, mini-size (2 mm diameter by 5 mm long) dosimeter element fabricated from Organic Plastic Scintillator (OPS) material was employed. Scintillation photon detection is accomplished using a precision photodiode and innovative signal amplification and processing techniques, rather than traditional photomultiplier tube methods. A significant improvement in signal to noise ratio, dynamic range and stability is achieved using this set-up. In addition, use of the non-saturating organic plastic scintillator material as the detector enables the dosimeter to measure beta radiation at very close distances to the source. In this work the plastic scintillators have been used to measure beta radiation dose at distances of less than 1 mm from an Sr-90 cardiovascular brachytherapy source having an activity of about 2.1 GBq beta radiation levels for both depth-distance and longitudinal profile of the source pellet chain, both in air and in liquid water, are measured using this system. The data obtained is compared with results from Monte Carlo simulation technique (MCNP 4B). Plastic scintillator dosimeter elements, when used in conjunction with photodiode detectors may prove to be useful dosimeters for cardiovascular brachytherapy beta sources, or other applications where precise near-source field dosimetry is required. The system described is particularly useful where measurement of actual dose rate in real time, a high level of stability and repeatability, portability, and immediate access to results are prime requirements.

Intravascular brachytherapy: indications and management of adverse events

Intravascular brachytherapy has become the standard of care for the treatment of coronary in-stent restenosis after repeat angioplasty. More than 5000 patients have been treated as part of various clinical trials. Based on the results of the GAMMA I trial, the START ((90)Sr Treatment of Angiographic Restenosis Trial), and the INHIBIT (INtimal Hyperplasia Inhibition with Beta In-stent restenosis Trial), the Checkmate system using (192)Ir, the Betacath system using (90)Sr/Y, and the Galileo system using (32)P, have been approved for the treatment of in-stent restenosis. With a better understanding and application of radiation oncology concepts to vascular brachytherapy, problems such as edge failure are being overcome. The complication of late thrombosis has also become less significant with the elimination of restenting at the brachytherapy procedure, and the prolonged use of antiplatelet therapy. There are other competing modalities in the early phases of clinical trials. The durability of results, lack of any significant long-term complications and the confirmation of the efficacy in other sites will further consolidate the role of radiation in treating in-stent restenosis.

Intracoronary beta brachytherapy as a treatment option for high-risk refractory in-stent restenosis

BACKGROUND

Vascular (VBT) has clearly been shown in multiple clinical trials to decrease restenosis rates for in-stent restenosis (ISR). However, patients enrolled in these randomized clinical trials represent a select group, and the efficacy of VBT in patients with ISR who were excluded from these controlled trials due to more complex coronary anatomy requires further investigation. This study sought to define the angiographic and clinical profile and outcomes of these high-risk patients with ISR who were excluded from the randomized clinical trials and who received VBTusing Strontium-90 (Sr-90) using the Novoste Beta-Cath System through a Compassionate Use Protocol (CUP).

METHODS

The study was designed as a single center, prospective, open label registry trial evaluating the use of VBT on complex instent restenotic lesions in patients who were excluded from the START and START 40 trials. In general, these patients included those with saphenous vein graft (SVG) lesions, long lesions (>35 mm), and patients with a history of more than three prior interventions. VBT using Sr-90 was delivered using the Novoste Beta-Cath System after successful angioplasty. The predetermined primary endpoint was freedom from target vessel revascularization (TVR) at 8 months, one and two years. The secondary endpoint was a composite of death, myocardial infarction (MI) and TVR at 8 months, one year, and two years.

RESULTS

Between September 4, 1998 and December 6, 2000, 32 patients were treated with VBT under the UCP protocol. The mean duration of follow up was 15.3 +/- 8.3 months. There were 9 major cardiac events at eight months including one death, one acute myocardial infarction and 7 TVR. Excluding the one patient who died, 33 lesions were available for follow-up. The rate of TVR in this high-risk patient population was 21.1% (n = 7/33 lesions). The method of revascularization included one bypass surgery and 6 repeat percutaneous coronary interventions.

CONCLUSIONS

This trial demonstrates that utilization of the Beta-Cath System using Sr-90 for the treatment of ISR in a patient population excluded from the randomized clinical trials due to unfavorable lesions characteristics is feasible appears to be associated TVR rates that compare favorably with the event rates of patients enrolled in other trials enrolling lower-risk groups.

Long-term follow-up of brachytherapy for treatment of allograft in-stent restenosis

The experience of brachytherapy in the treatment of in-stent restenosis of allograft arteries is limited. We present two cases of in-stent restenosis treated with brachytherapy with favorable angiographic follow-up at 10 months in one patient and at 17 months in the other.

Comparison of the angiographic outcomes after beta versus gamma vascular brachytherapy for treatment of in-stent restenosis

This study was designed to compare the angiographic outcomes of beta versus gamma vascular brachytherapy (VBT). We reviewed the angiographic results of 636 lesions (212 that underwent beta and 212 that underwent gamma VBT, and 212 that received placebo) with native coronary in-stent restenosis matched for lesion length, vessel size, preprocedure minimum lumen diameter (MLD), and time to angiographic follow-up in the various randomized clinical trials and studies. Baseline lesion complexity was similar in these 3 groups. Final MLD was smaller in the beta VBT group than in the gamma VBT or placebo group. At follow-up, beta and gamma VBT significantly reduced both angiographic restenosis (34.4% for beta VBT, 26.4% for gamma VBT, and 50.9% in the placebo group; p <0.0001) and recurrent lesion length (9.2 mm for beta VBT, 8.4 mm for gamma VBT, and 15.5 mm placebo, p <0.0001) compared with placebo. Gamma VBT was associated with a greater reduction in restenosis outside the stent than beta VBT. By multivariable analysis, independent angiographic predictors of treated segment restenosis included beta or gamma VBT, lesion length, and vessel size. In matched lesions, beta and gamma VBT achieved similar reductions in treated segment restenosis and recurrent lesion length compared with placebo.

Correlates of failure following treatment with Sr-90 beta irradiation for in-stent restenosis

We sought to determine the correlates of failure following intracoronary radiation therapy (IRT) with Sr-90 using the Novoste Beta-Cath system for the treatment of in-stent restenosis (ISR) in a broad range of patients. IRT has been shown to be more efficacious compared to placebo for the treatment of ISR in large randomized trials. However, even in patients treated with IRT, major adverse cardiac events occur in approximately 20% of cases on follow-up. This trial sought to elucidate the correlates of failure following successful IRT for ISR. To determine the correlates of IRT failure, we retrospectively compared the demographics, lesion characteristics, and clinical outcomes of 102 consecutive patients with ISR treated with Sr-90 from September 1998 to July 2001. IRT failure was defined as death, myocardial infarction (MI), or target vessel revascularization (TVR) due to repeat ISR on follow-up. A comparison of the clinical and angiographic profile of IRT failures (n = 16) vs. IRT successes (n = 86) revealed that a history of smoking (75% vs. 40%; P = 0.012), current use of calcium channel blockers (84% vs. 45%; P = 0.013), ostial location of target lesion (44% vs. 16%; P = 0.020), and mean posttreatment minimal luminal diameter (MLD; 1.64 +/- 0.19 vs. 2.21 +/- 0.29 mm; P < 0.001), respectively, were correlated with failure using univariate analysis. After multivariate regression analysis, the correlates of failure that remained significant were treatment of an ostial lesion (OR = 31.2; 95% CI = 2.6-382.7; P = 0.007) and final posttreatment MLD (P < 0.001). Ostial location of target lesion and smaller posttreatment MLD are correlated with subsequent death, MI, and TVR following therapy with Sr-90 for ISR.

Intravascular brachytherapy for native coronary ostial in-stent restenotic lesions

OBJECTIVES

We analyzed the effects of vascular brachytherapy (VBT) on ostial in-stent restenosis (ISR).

BACKGROUND

In-stent restenosis has a high recurrence rate after percutaneous reintervention. The recurrence rate of ostial ISR lesions and the impact of VBT remain unknown.

METHODS

We evaluated 133 patients with native coronary ostial ISR from a pooled database of 990 patients enrolled in randomized VBT trials. Independent quantitative angiography was performed at baseline and follow-up in 45 gamma, 27 beta, and 61 placebo patients.

RESULTS

Binary restenosis was significantly higher in placebo than radiated patients (75.4% vs. 17.8% in gamma vs. 22.2% in beta, p < 0.0001). The treatment effect of both gamma (odds ratio [OR] 0.06; 95% confidence interval [CI] 0.02 to 0.17) and beta VBT (OR 0.10; 95% CI 0.03 to 0.31) was maintained after controlling for differences in baseline lesion length. Proximal and distal radiation edge restenosis rates were similar among the groups. Vascular brachytherapy of true aorto-ostial lesions (n = 34) was similarly beneficial: restenosis rates of placebo versus gamma or beta patients of 83.3% versus 6.7% versus 28.6%, p = 0.0002.

CONCLUSIONS

Conventional treatment of ostial ISR is associated with a recurrence rate of over 75%. Vascular brachytherapy with either gamma or beta sources results in significant and similar reductions in restenosis compared with placebo. Similar benefits after VBT prevail in true aorto-ostial lesions.

Dosimetry characterization of a 32P source wire used for intravascular brachytherapy with automated stepping

Depth-dose curve measurements and Monte Carlo simulations for a catheter-based 32P intravascular brachytherapy source wire are described. The measured dose rates were obtained using both radiochromic-dye film and an extrapolation chamber (EC). Calibrated radiochromic-dye films were irradiated at distances between 0.5 and 5 mm from the source axis in polystyrene phantoms, and scanned with high-resolution densitometers. Measurements with an automated EC with a 1 mm diameter collecting electrode were also performed at a distance of 2 mm from the source in polystyrene. The measured dose rates obtained from the film and EC were divided by the measured source activity to obtain measured values of dose rate per unit contained activity. Dosimetric calculations of the catheter-based 32P wire geometry were also obtained using several Monte Carlo codes (CYLTRAN, MCNP, PENELOPE, and EGS). The measured and calculated values of dose rate per unit contained activity are in good agreement (<10%) within the relevant treatment distances (1 to 4 mm). With carefully selected input parameters, the calculated depth-dose curves using these codes were within 5% at 4 mm depth. At greater depths the discrepancies between the codes increase. We discuss likely mechanisms for these differences.

Reno, a European postmarket surveillance registry, confirms effectiveness of coronary brachytherapy in routine clinical practice

PURPOSE

To assess, by a European registry trial, the clinical event rate in patients with discrete stenotic lesions of coronary arteries (de novo or restenotic) in single or multiple vessels (native or bypass grafts) treated with beta-radiation.

MATERIALS AND METHODS

Between April 1999 and September 2000, 1098 consecutive patients treated in 46 centers in Europe and the Middle East with the Novoste Beta-Cath System were included in Registry Novoste (RENO).

RESULTS

Six-month follow-up data were obtained for 1085 patients. Of 1174 target lesions, 94.1% were located in native vessels and 5.9% in a bypass graft; 17.7% were de novo lesions, 4.1% were restenotic, and 77.7% were in-stent restenotic lesions. Intravascular brachytherapy was technically successful in 95.9% of lesions. Multisegmental irradiation, using a manual pullback stepping maneuver to treat longer lesions, was used in 16.3% of the procedures. The in-hospital rate of major adverse cardiac events was 1.8%. At 6 months, the rate was 18.7%. Angiographic follow-up was available for 70.4% of the patients. Nonocclusive restenosis was seen in 18.8% and total occlusion in 5.7% of patients. A combined end point for late (30-180 days) definitive or suspected target vessel closure was reached in 5.4%, but with only 2% of clinical events. Multivariate analysis was performed for major adverse cardiac events and late thrombosis.

CONCLUSIONS

Data obtained from the multicenter RENO registry study, derived from a large cohort of unselected consecutive patients, suggest that the good results of recent randomized controlled clinical trials can be replicated in routine clinical practice.

Calibration and validation of a quality assurance system for 90Sr/90Y radiation source trains

A quality assurance system (OPTIDOS, PTW-Freiburg) developed for dose rate verification of 90Sr/90Y radiation source trains (RSTs) was calibrated and validated. These source trains are used in the 5-F-BetaCath system (Novoste Corp.) for the treatment of endovascular diseases. The calibration factor of the OPTIDOS system was obtained empirically and is valid for 90Sr/90Y dose rate measurements at the specification point which is located at 2 mm distance from the source axis. A total of 187 OPTIDOS dose rate verifications of the 5-F-BetaCath system were performed in different hospitals. The histogram of the deviation between the manufacturer's dose rate specification and the dose rate measured using the OPTIDOS dosimetry system is Gaussian shaped with +/- 3% relative width and a mean shift of about +2% with respect to the corresponding dose rate specification. Additionally, 128 OPTIDOS dose rate verifications of the new jacketed RST (3.5-F-BetaCath, Novoste Corp.) were performed using the same calibration factor as derived for the 5-F-BetaCath system. Distribution of the deviation between the certified and the measured dose rate is nearly identical in comparison to the histogram of the 5-F-BetaCath system. The mean value of the deviations is shifted by -1.5% with respect to the certified dose rate. In order to compare the results of the calibrated OPTIDOS dosimetry system with a standard measuring method, separate dose rate measurements were performed using electron accelerator calibrated radiochromic films in which calibration is traceable to PTB (Physikalisch Technische Bundesanstalt, Germany). Deviation between both the methods is less than 3.1%. These results confirm that the calibrated OPTIDOS dosimetry system can be considered suitable for quality assurance of both types of RST used in the BetaCath systems.

Dose effects of stents in intravascular brachytherapy for in-stent restenosis: a Monte Carlo calculation

PURPOSE

Intravascular brachytherapy (IVBT) has been recognized as a preferred treatment for coronary in-stent restenosis (ISR) in routine practice. Stents made of high-Z materials will inevitably perturb the dose distribution of IVBT. In this work, we have conducted a systematic study on these dose perturbations for three commercially available IVBT sources.

METHODS AND MATERIALS

The EGSnrc Monte Carlo codes were used to calculate the dose distributions for the 90Sr, 32P, and 192Ir IVBT sources with and without a metallic stent in place. The ring stent type made of different material and with different strut size, metallic surface area (MSA), and radius was studied.

RESULTS

Calculations show that dose enhancement of 5% to 20% occurs inside stent in the region close to the stent struts (luminal side) for all three sources. In the region outside stent (adventitial side), dose reduction of 5% to 20% is observed for a beta source, whereas the dose effect is negligible for the gamma source. For a given stent design, the tantalum stent yields a larger dose effect than other stents made of steel, Ti, Ni, or nitinol. It is found that the dose effect significantly depends on strut thickness, and it is strongly correlated to MSA. The MSA may be used to characterize the dose effect of a stent. Sample empiric equations to relate the dose perturbations to MSA for a given source, a stent material, and a strut thickness were derived.

CONCLUSIONS

The dose perturbations due to the presence of metallic stents were found to be significant in IVBT for ISR. The dose effects of a stent can be estimated from its MSA based on derived empiric equations. The data presented are practically useful to consider the dose effects of stents in dose evaluation/treatment planning for using IVBT to treat ISR.

A break-even price calculation for the use of sirolimus-eluting stents in angioplasty

BACKGROUND

One of the major complications of angioplasty is the early occurrence of restenosis requiring a repeat procedure. When bare-metal stents are used, clinical restenosis results in a repeat procedure in 10% to 15% of cases. Based on the results of an international, randomized clinical trial, the use of sirolimus-eluting stents reduces this risk.

OBJECTIVES

The aims of this study were to calculate the theoretical break-even price for sirolimus-eluting stents in France, the Netherlands, and the United States, and to determine the additional health care cost per patient.

METHODS

The break-even price was calculated by adding the savings resulting from a 15% decrease in the rate of clinical restenosis to the price of bare-metal stents. Costs were computed from the viewpoint of the health care system, exclusive of other societal costs.

RESULTS

The break-even prices were 1291 Euro to 1489 Euro in France, 2028 Euro in the Netherlands, and 2708 Euroin the United States (1.00 Euro = 1.00 US dollar in purchasing power parity). These results indicate that the commercial price of sirolimuseluting stents will increase hospital spending for patients undergoing angioplasty by 17% to 55% per patient.

CONCLUSION

This additional cost to the health care system should be discussed in view of possible productivity savings and improved quality of life for patients.

[Brachytherapy for coronary restenosis: state of art in 2003]

Based on therapeutic approach for benign diseases, vascular brachytherapy decreases smooth vascular muscle cells proliferation and multiplication which lead to the formation of the neo-intima. The radioactive positive action affects arterial recoil due to post angioplasty vessel injury. Randomised studies has shown good angiographic results up to 6 months of follow-up, with 50% in-stent restenosis rate decrease and on the analysed segment as well. Decrease on Mace and TLR show statistically significance. Results don't correlate with emitter and bêta emitters had been introduced in France recently. Vascular brachytherapy is actually indicated for in-stent restenosis, there is no evidence to perform this treatment for de novo lesion. Geographic miss, source centering, late thrombosis and pullback procedure may interfere with treatment quality. IVUS allows best target volume determination to a higher quality level. Internationals guidelines such as Eva-Gec-Estro recommendations could increase treatment safety and enable development of an optimal technique.

Predictors of late cardiac events following treatment with Sr-90 beta-irradiation for instent restenosis

BACKGROUND

Intracoronary radiation therapy (IRT) with Sr-90 using the Novoste Beta-Cath system has been shown to be an effective therapy for instent restenosis (ISR), but the temporal occurrence of cardiac events and the predictors of late complications require further investigation.

METHODS

We analyzed the demographics, lesion characteristics and clinical outcomes of 138 consecutive patients with ISR treated with IRT from September 1998 to March 2002. Major adverse cardiac events (MACE) were defined as death, myocardial infarction (MI) or target vessel revascularization (TVR). Characteristics of early (< or =8 months) and late (>8 months) failures were analyzed.

RESULTS

Thirty-two (23.1%) of 138 patients had MACE on follow-up; 25% (8/32) of failures occurred late after treatment with IRT. A comparison of the clinical and angiographic profile of early and late failures using univariate analysis indicates no correlations to late failure following IRT. Duration to failure after IRT was 14.25+/-3.69 months in the late group compared to 4.63+/-2.86 months in the early group (P<.001).

CONCLUSIONS

Late MACE after IRT with Sr-90 for ISR occur beyond the traditional period for clinical restenosis in 25% of cases and are difficult to predict. Further study is warranted to identify patients at risk for the development of late complications after IRT.

Geographical miss and restenosis during catheter-based intracoronary beta-radiation for de novo lesions

OBJECTIVES

We sought to determine the impact of geographical miss (GM) on restenosis rates after intracoronary beta-radiation therapy for de novo lesions.

BACKGROUND

GM is the situation in which injured vessel segments (VSs) are receiving low-dose radiation and is accounted for edge restenosis. Its impact on the overall restenosis rates remains to be determined.

METHODS

We analyzed 330 patients (356 vessels) treated according to the Beta Radiation in Europe (BRIE) and the Dose Finding study protocols. Using quantitative coronary angiography (QCA), the effective irradiated segment (EIRS), its edges and the total VS were analysed. The edges of the EIRS that were injured constituted the GM edges. Restenosis was defined as diameter stenosis > 50% at follow-up. GM was determined by the simultaneous electrocardiographic-matched, side-by-side projection of the source and balloons deflated and surrounded by contrast, at the site of injury, in identical angiographic projections.

RESULTS

In 20.5% of the vessels, GM was non-interpretable due to inadequate filming. GM occurred at 30.4% of the interpretable edges and 53% of the interpretable vessels that were analysed. Edge restenosis was significantly increased in the GM compared to non-GM edges (13.16% vs. 4.17%, respectively, P = .001), both in the proximal (P = .03) and the distal (P = .001) edges. GM associated with stent injury significantly increased edge restenosis (P = .006). GM related to balloon injury tended to be associated with increment in edge restenosis (P = .07). The restenosis in the EIRS was similar between vessels with and without GM (17.78% and 14.85%, respectively, P = .6). GM was associated with significant increment in the restenosis at the analyzed VS (31.85% vs. 21.48%, P = .05).

CONCLUSIONS

GM is strongly associated with edges and restenosis in the analysed VS. GM does not increase restenosis in the EIRS.

Visual assessment of procedural results following treatment with Sr-90 beta-radiation for instent restenosis

BACKGROUND

Visual assessment (VA) of postprocedural % diameter stenosis (DS) is used routinely in clinical practice to determine the adequacy of coronary intervention. Although VA has been shown to underestimate final %DS after balloon angioplasty compared to quantitative coronary angiography (QCA), the impact of this effect on clinical outcomes following treatment with intracoronary radiation therapy (IRT) with Sr-90 for instent restenosis (ISR) is unknown.

METHODS

To determine the effect of VA on the rate of major adverse cardiac events (MACEs) after IRT for ISR, we compared the clinical outcomes of 102 consecutive patients based on postprocedural %DS by QCA vs. %DS by VA. MACE was defined as death, M1 or need for target vessel revascularization (TVR).

RESULTS

MACE rates for the 102 consecutive patients grouped according to postprocedural %DS by QCA and VA were compared. The mean %DS by QCA was 30.7%, while the mean %DS by VA was 12.5%. The mean %DS by VA across the QCA subgroups were 13.67%, 10.71% and 13.37%, respectively (P = .244). Fifty-two patients (51.0%) had %DS > 30% by QCA with the highest MACE percentage occurring in this subgroup.

CONCLUSION

VA underestimated the %DS compared to QCA, and it was associated with worse MACE following treatment with Sr-90 for ISR.

External beam irradiation in angioplasted arteries of hypercholesterolemic rabbits. The dose and time effect

PURPOSE

To study the dose and time effect of external beam irradiation on the morphometry of both angioplasted and nonangioplasted arteries in a hypercholesterolemic rabbit model.

METHODS AND MATERIALS

Eight groups of rabbit femoral arteries were studied: arteries (a) with no intervention, (b) irradiated with a 12-Gy 6 MV X-ray dose, (c) with a 18-Gy, (d) treated with balloon angioplasty, (e) dosed with 12-Gy half an hour post-angioplasty, (f) dosed with 18-Gy half an hour post-angioplasty, (g) dosed with 12-Gy 48 h post angioplasty, (g) dosed with 18-Gy 48 h post angioplasty.

RESULTS

External irradiation at either 12 or 18 Gy was not found to change vessel morphometry in noninjured arteries. The 12-Gy dose given soon after angioplasty further increased percentage stenosis (63% on the average), despite the preservation of the lumen cross-sectional area. Positive remodeling was not observed in arteries given 18-Gy half an hour post angioplasty to counterbalance the increased neointimal formation. Therefore, this treatment resulted in a drastic reduction in lumen area and in enhancement of percentage stenosis (84% on the average). On the contrary, the delayed irradiation of the angioplasted arteries at either 12 or 18 Gy was not found to influence any of the studied morphometric parameters 5 weeks after angioplasty.

CONCLUSIONS

Uniform external beam irradiation up to 18 Gy was well tolerated by intact femoral arteries. Prompt 12- or 18-Gy irradiations accentuated percentage stenosis. However the lumen cross-sectional area was preserved only at the lower dose point. Delayed irradiation at any dose did not influence the restenosis process.