FDA approval of coronary-artery brachytherapy

Is Coronary Brachytherapy Staging a Comeback for the Treatment of In-Stent Restenosis?

PURPOSE OF REVIEW

The catheter-based coronary intervention has become a well-established therapeutic modality for obstructive coronary artery disease. However, in-stent restenosis remains a significant limitation of coronary intervention despite the use of newer devices. Intravascular brachytherapy was introduced to treat recurrent in-stent restenosis but only modestly adopted. This review will discuss the mechanism of intracoronary brachytherapy, available clinical evidence of brachytherapy in recurrent in-stent restenosis treatment, and the future of coronary brachytherapy in coronary intervention.

RECENT FINDINGS

Drug-eluting stents have an inherent limitation as they leave a permanent metal layer inside an artery when deployed. Recently, drug-coated balloon technology has emerged to treat coronary artery disease as a combination of balloon angioplasty and local drug delivery without leaving a metal layer behind. Recent European guidelines recommended using drug-coated balloons when treating in-stent restenosis treatment, while the US guidelines have not yet addressed the use of drug-coated balloons in such cases. Coronary brachytherapy is a valuable addition to treat these challenging diseases despite several logistic issues. If there are newer technologies with easier setup, such as drug-coated balloons, coronary brachytherapy resurgence is improbable in the contemporary era, although it may not become obsolete.

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.

Intravascular brachytherapy for peripheral vascular disease

BACKGROUND

Interventional treatment of arteries that are narrowed and obstructed by atherosclerosis involves either bypassing the blockage using a graft; widening the artery from the inside with a balloon, a procedure known as percutaneous transluminal angioplasty (PTA); or providing a strut to hold the vessel open, known as a stent. All of these treatments are, however, limited by the high numbers that fail within a year. Intravascular brachytherapy is the application of radiation directly to the site of vessel narrowing. It is known to inhibit the processes that lead to restenosis (narrowing) of vessels and grafts after treatment. This is an update of a review first published in 2002.

OBJECTIVES

To assess the efficacy of, and complications associated with, intravascular brachytherapy (IVBT) for maintaining patency after angioplasty or stent insertion in native vessels or bypass grafts of the iliac or infrainguinal arteries.

SEARCH METHODS

For this update the Cochrane Peripheral Vascular Diseases Group Trials Search Co-ordinator searched their Specialised Register (last searched August 2013) and CENTRAL (2013, Issue 7).

SELECTION CRITERIA

Randomised controlled trials of the use of brachytherapy as an adjunct to the endovascular treatment of people with peripheral arterial disease (PAD) or stenosed bypass grafts of the iliac or infrainguinal arteries versus the procedure without brachytherapy.

DATA COLLECTION AND ANALYSIS

Two review authors independently assessed trial quality and two other review authors independently extracted the data. Adverse event information was collected from the trials.

MAIN RESULTS

Eight trials with a combined total of 1090 participants were included in this review. All included studies used the femoropopliteal artery. We did not identify any studies that used the iliac arteries. All studies compared PTA with or without stenting plus IVBT versus PTA with or without stenting alone. No trials were found comparing IVBT to technologies such as drug eluting stents or balloons, or cryoplasty. Follow-up ranged from six months to five years. The quality of the included trials was moderate with our concerns relating to the difficulty of blinding due to the nature of the procedures and the small sample sizes for some studies. Primary outcomes (patency or restenosis and need for re-intervention) were reported in the majority of the trials, but reporting at various time points and the use of multiple definitions of the outcomes by the included studies meant that not all data were available for pooling. The secondary outcomes were not reported in many of the included studies.For brachytherapy, cumulative patency was higher at 24 months (odds ratio (OR) 2.36, 95% confidence interval (CI) 1.36 to 4.10, n = 222, P = 0.002). A statistically significant difference was found for restenosis at six months (OR 0.27, 95% CI 0.11 to 0.66, n = 562, P = 0.004), 12 months (OR 0.44, 95% CI 0.28 to 0.68, n = 375, P = 0.0002) and 24 months (OR 0.41, 95% CI 0.21 to 0.78, n = 164, P = 0.007) in favour of IVBT. No difference was found after five years as measured in one study. The need for re-interventions was reported in six studies. Target lesion revascularisation was significantly reduced in trial participants treated with IVBT compared with angioplasty alone (OR 0.51, 95% CI 0.27 to 0.97, P = 0.04) at six months after the interventions. No statistically significant difference was found between the procedures on the need for re-intervention at 12 and 24 months after the procedures.A statistically significant lower number of occlusions was found in the control group at more than three months (OR 11.46, 95% CI 1.44 to 90.96, n = 363, P = 0.02) but no differences were found at less than one month nor at 12 months after the procedures making the clinical significance uncertain. Ankle brachial index was statistically significantly better for IVBT at the 12 month follow-up (mean difference 0.08, 95% CI 0.02 to 0.14, n = 100, P = 0.02) but no statistically significant differences were found at 24 hours and at six months.Quality of life, complications, limb loss, cardiovascular deaths, death from all causes, pain free walking distance and maximum walking distance on a treadmill were similar for the two arms of the trials with no statistically significant difference found between the treatment groups.

AUTHORS' CONCLUSIONS

The evidence for using peripheral artery brachytherapy as an adjunct to percutaneous transluminal angioplasty to maintain patency and for the prevention of restenosis in people with peripheral vascular disease is limited, mainly due to the inconsistency of assessment and reporting of clinically relevant outcomes. More data are needed on clinically relevant outcomes such as health related quality of life (HRQOL) or limb salvage and longer-term outcomes, together with comparisons with other techniques such as drug eluting balloons and stents. Adequately powered randomised controlled trials, health economics and cost-effectiveness data are required before the procedure could be recommended for widespread use.

From basic biology to randomized clinical trial: the Beta Radiation for Arteriovenous Graft Outflow Stenosis (BRAVO II)

The BRAVO-II study was a randomized controlled study of endovascular radiation therapy as compared to sham radiation therapy, following angioplasty of a thrombosed PRFE graft. The results did not show a benefit of endovascular radiation therapy, albeit in the context of an early termination of the study at less than 50% enrollment due to business reasons. Emphasis is laid on the fact that there may still be a role for radiation therapy in specific clinical settings associated with dialysis vascular access dysfunction.

External Beam Irradiation and Restenosis Following Femoral Stenting: Long-Term Results of a Prospective Randomized Study

PURPOSE

To assess the long-term outcome of external beam irradiation (EBI) for the prevention of restenosis due to neointimal hyperplasia, following percutaneous transluminal angioplasty (PTA) and stenting of the superficial femoral artery.

METHODS

Sixty consecutive patients with peripheral arterial disease, who were treated with "bail-out" stent implantation in the superficial femoral artery due to suboptimal PTA, were included in this study. Patients were randomly allocated into two groups, receiving either external beam irradiation (6 MV photons, total dose 24 Gy in a hypofractionated schedule) plus antiplatelet therapy (EBI group) or antiplatelet therapy alone (control group).

RESULTS

No procedure-related complications occurred, and all patients of the EBI group received the full dose of 24 Gy. During the long-term follow-up, an overall statistically significant difference was demonstrated in favor of the EBI group patients, regarding both the in-stent (log-rank test, p = 0.0072) and the in-segment binary restenosis (log-rank test, p = 0.0103). The primary patency rates were also significantly better in the EBI group at specific time-points, such as in the first (74.2% vs 46.5%, p = 0.019), second (62.5% vs 33.8%, p = 0.020), and third (54.6% vs 29.0%, p = 0.039) year, respectively. Moreover, the overall clinically driven reintervention rate was significantly lower among patients of the irradiated group (log-rank test, p = 0.038).

CONCLUSION

Our long-term follow-up analysis revealed that EBI following femoral artery PTA and stenting significantly reduces restenosis and reintervention rates, while improving primary patency.

Prevention of coronary restenosis with radiation therapy: a review

The problem of restenosis after percutaneous transluminal coronary angioplasty remains the major limiting factor of the procedure. Over the last 10 years, investigators have been studying the use of radiation therapy for preventing restenosis after angioplasty or stent placement. Since radiotherapy has been proven in other cases to be effective in disrupting the cell cycle regulatory proteins and thereby slowing or stopping growth, it was decided to apply the same principle to neointimal hyperplasia. To review the data that have emerged regarding vascular radiation with an emphasis on irradiated stents, 65 articles were reviewed and both preclinical and clinical experiments were included. Overall, studies with gamma and beta radiation show promising results. Endovascular gamma radiation has been shown effective in randomized trials, even at 3-year follow-up. Beta radiation is preferred because of greater safety and localization, and because it has also shown encouraging results in initial clinical trials, as well as in larger randomized studies. Consequently, the Federal Drug Administration has approved the use of both. In both types of endovascular brachytherapy, it seems the greater the dose, the better the initial response. Safety concerns include an increased incidence of late thrombosis and greater restenosis at margins. With irradiated stents, however, the situation is not as clear. At times, animal models have presented confusing results. These have ranged from significant suppression of hyperplasia to outright adverse effects of radiation on the vessel wall. While some clinical trials have been encouraging, others have not. Follow-up of up to 1 year has been disappointing so far. Many issues, such as the "candy wrapper" effect and rebound hyperplasia, must be dealt with before this becomes a viable form of therapy. It has become clear that radiation therapy in this setting, while having potentially great benefits, can cause deleterious effects as well. However, the mixed bag of positive and negative results seen so far, and the attractiveness of stents or percutaneous transluminal coronary angioplasty being "restenosis-proofed," eventually is cause for cautious optimism.

BRAVO I: A pilot study of vascular brachytherapy in polytetrafluoroethylene dialysis access grafts

Hemodialysis vascular access dysfunction owing to stenosis and thrombosis in polytetrafluoroethylene dialysis access grafts is a huge clinical problem for which there are currently no long lasting durable therapies. Vascular brachytherapy has been used successfully for the prevention of coronary restenosis following angioplasty and stent placement. The Beta Radiation for Treatment of Arterial-Venous Graft Outflow I study was a pilot study of vascular brachytherapy in hemodialysis patients with patent but dysfunctional grafts. Twenty-five patients were randomized to receive either radiation therapy (a single dose of 18.4 Gy) or sham radiation, following angioplasty. The primary efficacy end point of the study was target lesion primary patency at 6 months. The primary safety end point was a composite of death, emergency surgery on the graft, venous rupture, or aneurysm formation. Forty-two percent of the radiated grafts achieved the target lesion primary patency end point at 6 months as compared to 0% of the control group (P = 0.015), but this did not translate into an improvement in secondary patency at either 6 or 12 months. Radiation therapy was found to be safe in the setting of hemodialysis vascular access dysfunction. Our results suggest that vascular brachytherapy is an intervention that is worthy of further examination in the setting of non-thrombosed dialysis access grafts.

Optimization of dose prescription protocol and its impact on delivered dose and vascular response after beta-radiation for in-stent restenosis. A randomized trial with serial volumetric intravascular ultrasound and dose volume histograms

AIM

The incidence of restenosis within stented segment after intravascular brachytherapy with recommended dose prescription protocols is up to 25%. Therefore, we designed a randomized trial comparing recommended dose prescription protocol with dosing adjusted for the source-to-target distance.

METHODS

Fifty-one in-stent restenosis (ISR) lesions in 48 patients underwent centered source beta-irradiation with serial intravascular ultrasound. Patients randomly received 20 Gy at 1 mm either beyond lumen surface [n=25, standard group (S)] or external elastic membrane [n=26, dosing-adjusted (DA) group]. Minimum dose absorbed by 90% of adventitia (DV(90%Adv)) was calculated.

RESULTS

DV(90%Adv) was higher for the DA group than for the S group (21.63+/-5.67 vs. 12.05+/-4.88 Gy, P<.001). After 8.9+/-4.5 months there was complete lumen preservation in DA vs. lumen decrease subsequent to neointimal hyperplasia (NIH) in S group (0.10+/-1.20 vs. -0.61+/-1.29 mm3/mm, P<.05). Vessel volume increased significantly in the DA group and was unchanged in S group (+1.73, P=.002 vs. 0.14 mm3/mm, P=NS). DV(90%Adv) correlated inversely with NIH volume and positively with vessel volume change (r=-.405, P=.007 and r=.363, P=.017, respectively).

CONCLUSION

For beta-irradiation of ISR, dosing adjusted for the source-to-target distance leads to significant increase in target delivered doses, which is associated with complete NIH inhibition and induction of positive vessel remodeling.

Key issues in end point selection for heart failure trials: composite end points

BACKGROUND

Composite outcomes are commonly used in heart failure trials. The aim of this article is to discuss the advantages and disadvantages of composite outcomes and recommend guidelines for reporting them. Examples are used to illustrate key points.

METHODS AND RESULTS

A workshop jointly planned by the Heart Failure Society of America and the US Food and Drug Administration was convened in April 2004. One of the panel discussions concerned the use of composite outcomes in heart failure trials. With use of composite outcomes, event rates are higher and if it is reasonable to assume that the treatment effect is similar for each component of the composite outcome, sample size will be smaller than using one of the components as the primary end point. Composites end points are difficult to interpret if effects are not similar for all components or if the effect of treatment is primarily on a more common, less serious component of the composite. Composite outcomes typically only focus on the first occurring event. This can lead to a substantial loss of information in some trials. When composite end points are used, data collection for all components should continue until the end of the trial so that each component can be separately evaluated.

CONCLUSION

Composite end points should be used with caution. Additional research is need on optimally weighting components of composite outcomes and to better using the entire event history of patients in heart failure trials. Further analyses of completed trials could be useful in this respect.

Long-term care after percutaneous coronary intervention: focus on the role of antiplatelet therapy

Arterial wall injury caused by percutaneous coronary intervention (PCI) triggers transient platelet activation and mural thrombosis; these effects are superimposed on the preexisting platelet hyperreactivity associated with underlying atherothrombosis. Platelet activation has been implicated in the major complications of PCI: acute and subacute thrombosis and restenosis. Antithrombotic and anticoagulant therapy minimizes thrombotic complications after PCI. Aspirin plus a thienopyridine (ticlopidine or clopidogrel) is more effective than aspirin plus heparin and extended warfarin therapy in preventing periprocedural ischemic events and subsequent stent thrombosis and results in less major and minor bleeding. Dual antiplatelet therapy with aspirin and clopidogrel (the preferred thienopyridine because of its superior hematologic safety) is recommended for at least 4 weeks to prevent subacute stent thrombosis with bare-metal stents and 3 to 6 months to prevent late-stent thrombosis with drug-eluting stents. Coronary atherothrombosis is a diffuse vascular disease, and reduction of the risk of future ischemic events requires strategies that extend beyond the focal treatment of stenotic lesions. Optimal long-term care after PCI requires aggressive systemic pharmacotherapy (antiplatelet agents, statins, beta-blockers, and angiotensin-converting enzyme Inhibitors) in conjunction with therapeutic lifestyle changes (smoking cessation, weight reduction, dietary measures, and exercise). In this context, dual antiplatelet therapy (aspirin plus clopidogrel) is recommended for at least 12 months after PCI for prophylaxis of future atherothrombotic events.

Serial angioscopic findings after successful intracoronary brachytherapy for in-stent restenosis

The intracoronary changes that occur after brachytherapy for in-stent restenosis (ISR) have yet to be fully established. The purpose of this study in patients who had ISR was to examine the serial angioscopic changes in intracoronary lesions that occurred after brachytherapy. Forty-four patients who had ISR (49 lesions) underwent balloon angioplasty (n = 34) or directional atherectomy (n = 15), followed by intracoronary brachytherapy using a beta-emitting phosphorus-32 source wire. Angioscopic investigations were performed 3 and 9 months after brachytherapy. Uncovered stents were detected in 63.3% of lesions at 3 months. A significant decrease (p = 0.028) in this prevalence occurred over the next 6 months, with 36% of lesions having uncovered stents at 9 months. At 3 months, 33% of the lesions had visible erosion or ulceration and superficial thrombus. The prevalence of these characteristics was decreased at 9 months, although 17% of the lesions were still ulcerated or eroded at that time. Protruding thrombus was not observed in any lesion at 3 and 9 months. In conclusion, uncovered stents and intimal erosions or ulcerations were still present 9 months after brachytherapy in 36% and 17% of lesions, respectively. These results suggest that the healing process was not completed 9 months after brachytherapy in approximately 33% of lesions.

Reduction of Intimal Hyperplasia withRe-188-labeled Stents in a Rabbit Model at 7and 26 Weeks: An Experimental Study

The aim of this study was to analyze the feasibility of (188)Re-labeled stents to reduce neointimal formation in a rabbit atherosclerosis model and to test the long-term effects at 7 and 26 weeks. Fifty-nine male New Zealand White rabbits were fed a 0.5% cholesterol diet for 4 weeks before balloon angioplasty and insertion of Palmaz stents in the infrarenal aorta. The animals were sacrificed 7 and 26 weeks after stent implantation. Control stents were compared with (188)Re stents: (dose 1) 11.3 +/- 1.8 MBq; (dose 2) 37.3 +/- 4.2 MBq, and (dose 3) 80.1 +/- 7.8 MBq. Each activity group consisted of a short-term (7 weeks) and a long-term group (26 weeks), resulting in a total of eight study groups. No thrombotic occlusion was observed. The neointimal formation in the control group was 2.11 [95% confidence interval (CI): 0.68--6.52] mm(2) at 7 weeks and 2.10 (0.62--7.11) at 26 weeks. In the treatment groups, neointima reduction was detectable at 7 weeks [dose 1: 0.33 (0.09--1.22) mm(2); dose 2: 0.17 (0.05--0.57) mm(2); dose 3: 0.03 (0.01--0.13) mm(2)]. After 26 weeks, a catch-up of neointimal formation in the radioactive groups was most obvious in the low-dose group [dose 1: 0.80 (0.28--2.29) mm(2); dose 2: 0.18([0.06--0.52) mm(2); dose 3: 0.50 (0.17--1.42) mm(2)]. Compared to the long-term control group, neointimal reduction was still >60%. No induction of neointimal formation was observed at the edges of the stents. Radiation resulted in delayed re-endothelialization. (188)Re stents were capable to reduce intimal hyperplasia and did not cause thrombosis. The edge effect, which was the major limitation of (32)P stents, was not observed in (188)Re stents.

Two-year clinical follow-up of 90Sr/90 Y beta-radiation versus placebo control for the treatment of in-stent restenosis

BACKGROUND

It is an ongoing concern that intracoronary brachytherapy may possibly just delay the problem of in-stent restenosis ("late catch up"). For gamma-radiation, 3 placebo-controlled studies have shown the maintenance of the initially positive effect after 2 years, but similar data do not exist for beta-radiation. STents And Restenosis Trial (START) was the first placebo-controlled randomized trial for in-stent restenosis with beta-radiation; herein, we report the 2-year clinical follow-up.

METHODS AND RESULTS

Two hundred and forty-four patients were randomized to active treatment, 232 patients to placebo (nonactive source train) treatment. The primary end point of efficacy was target vessel revascularization (TVR); primary safety end point was any major adverse cardiac event (MACE) at 8 months and 2 years. Two-year clinical outcome in patients receiving brachytherapy was based on 195 of 244 original patients (79.9%) and in the placebo arm on 183 of 232 original patients (78.9%). TVR was significantly reduced by 25%; from 36.6% (placebo) to 27.5% (brachytherapy) remained significant after 2 years (RR .7 [.57-.98], 95% CI -9.2 [-17.5-0.8]). The Kaplan-Meier analysis for TVR and MACE showed improvement beginning approximately 90 days after radiation and remained almost constant for the 2 following years. Freedom from TVR was significantly increased from 62.4% +/- 3.8% to 71.6% +/- 3.3% (P = .027) and freedom from MACE from 58.9% +/- 3.7% to 68.0% +/- 3.4% (P = .035).

CONCLUSIONS

The START trial shows for the first time that the initial beneficial effects of intracoronary brachytherapy with beta-radiation using 90 Sr/ 90 Y are maintained at 2-year clinical follow-up period.

Late thrombosis following treatment of in-stent restenosis with drug-eluting stents after discontinuation of antiplatelet therapy

Drug-eluting stent usage has become commonplace for the percutaneous treatment of de novo coronary lesions, but the safety and efficacy profile for their evolving usage in restenotic lesions is largely unknown. We report three cases of angiographically confirmed drug-eluting stent thrombosis following treatment of restenotic lesions that occurred late (193, 237, and 535 days) and shortly after interruption of antiplatelet therapy. All three patients suffered ST elevation myocardial infarction, and there was one death. Further studies are necessary to better define the associated risk and ideal duration of antiplatelet therapy necessary in this cohort of patients with restenotic lesions.

Willingness to pay for avoiding coronary restenosis and repeat revascularization: results from a contingent valuation study

BACKGROUND

Despite technological improvements, percutaneous coronary intervention (PCI) remains limited by restenosis requiring further revascularization procedures during the ensuing year. New technologies aiming to reduce restenosis are expensive and may increase net healthcare costs. Economic evaluations of such therapies have been performed, but have been hindered by the need to assess the disutility of short-term health care events and repeat coronary revascularization as well as the lack of benchmark standards for intermediate health outcomes. The contingent valuation approach may offer particular advantages when evaluating treatments that improve short-term health outcomes.

OBJECTIVE

To examine patients' willingness to pay (WTP) for treatments that may reduce the risk of restenosis and repeat revascularization after PCI.

METHODS

We used a contingent valuation approach to evaluate WTP among participants in two large clinical trials evaluating new PCI devices. The baseline scenario described a 30% probability of repeat revascularization following the initial procedure. Patients were asked to indicate, using a close-ended (referendum) question, their out of pocket WTP for an improved treatment that would reduce this risk. Three different prices (500 dollars, 1000 dollars, and 1500 dollars) and three levels of absolute risk reduction (10, 20, and 30%) were randomly varied creating nine sub-samples of patients. Patients' responses were analyzed using both parametric and non-parametric methods.

RESULTS

1642 patients completed the WTP question. The WTP medians for the 10 and 20% risk reductions were 273 dollars and 366 dollars, respectively; the median WTP for the 30% risk reduction was significantly higher at 1162 dollars (P<0.001). Higher household income (OR=1.57, P<0.001) was independently associated with a higher WTP.

CONCLUSIONS

Although short-lived, avoidance of coronary restenosis may have considerable value to patients undergoing percutaneous coronary interventions. These findings may have important implications for emerging technologies such as drug-eluting stents.

Radionuclides-hyaluronan-conjugate thromboresistant coatings to prevent in-stent restenosis

Catheter-based brachytherapy is one of the most effective modalities to inhibit hyperplasia following revascularization procedures. Radioactive stents have failed, however, to prevent clinical hyperplasia due to excessive late lumen loss on the edge of the devices. Numerous strategies have been proposed to circumvent the drawbacks of irradiation therapies, such as the use of more appropriate radionuclides or the "hot-end" stents approach. This paper describes versatile radioactive devices obtained by coating plasma functionalized surfaces-stents or catheters-with a hyaluronan (HA)-diethylenetriamine pentaacetic acid (DTPA) conjugate (HA-DTPA) complexed with a gamma or beta radionuclide. Yttrium and indium were used as radionuclide models, due to their suitability for endovascular radiotherapy. X-ray photoelectron microscopy and time-of-flight secondary ions mass spectrometry analyses confirmed the successful immobilization of the HA-DTPA conjugate on both the metallic (NiTi) and polymeric (Teflon) plasma functionalized surfaces. HA-DTPA-coated surfaces were significantly more hydrophilic than bare surfaces (39.5 degrees vs. 67 degrees on NiTi substrate and 29 degrees vs. 128 degrees on Teflon substrate). Therapeutic doses of yttrium and indium were easily loaded onto the surfaces and remained stable over 2 weeks with a radionuclide loss of about 6%. The HA-DTPA-coated Teflon surfaces presented significantly less fibrinogen adsorption than uncoated materials in an in vitro flow model. This approach, which combines the hemocompatibility of HA-coated surfaces and the anti-proliferative effects of an appropriate radiotherapy, constitutes a promising methodology to alleviate the restenosis induced by existing devices.

Two-year outcomes of repeated brachytherapy in patients with restenosis after intracoronary radiation therapy

This study compared the 2-year outcomes of repeat brachytherapy (n = 10) and conventional percutaneous intervention (n = 14) in patients with restenosis after intracoronary brachytherapy with a rhenium-188-filled balloon system. The short-term target lesion revascularization rate was significantly lower in the repeat brachytherapy group (0% vs 36%, p = 0.038), and additional target lesion revascularization was required in 2 patients with repeat brachytherapy during 2-year follow-up. There were no vascular complications related to repeat brachytherapy.

New strategies to prevent restenosis

The Holy Grail of cardiovascular pharmacology has been the search for an effective therapy targeting restenosis after angioplasty and/or intra-arterial stenting. The failure of promising therapeutics in clinical trials underscores the complexity and redundancy of the signaling cascades regulating mitogenesis and fibrogenesis. Novel therapeutic modalities have potential to target dysfunctional signaling elements directly in vascular smooth muscle cells. Significant progress in the treatment against restenosis will require the exploitation and cross-fertilization of developments in the fields of pharmacology, bioengineering, genetics, and molecular biology. Collaboration among researchers in these fields will be essential.

Brachytherapy for in-stent restenosis in general interventional practice: a single institution's experience using four radiation devices

BACKGROUND

The effectiveness of brachytherapy for the treatment of in-stent restenosis (ISR) has been established in a number of large randomized controlled trials. Efficacy of this therapy in general population is less well established.

METHODS AND MATERIALS

We report our experience of 207 patients, 236 coronary lesions, treated with brachytherapy between November 2000 and November 2002. All commercially available brachytherapy devices, as well as one investigational device, were utilized. This cohort was followed over 9 months and clinical outcomes were obtained with subsequent analysis of patient and lesion-specific characteristics.

RESULTS

Average treatment age was 62.5 years; 73% were male and the most frequent presentation was unstable angina (74%). All patients had successful delivery of radiation, with no in-hospital deaths. Novoste BetaCath device was used for 163 (65%) lesions, Cordis Checkmate for 56 (24%) lesions, Interventional Therapies device in 13 (8%) lesions, and Guidant Galileo in 4 lesions (3%). At a mean follow-up of 9.1 months, 78.7% were free of major adverse cardiac event (MACE). Twenty-one patients required repeat PTCA (10.1%), 19 had CABG (9.2%), 3 had MI (1.4%), and there was 1 death (0.5%). Unadjusted MACE rates for each device were 21% for Novoste, 28% for Checkmate, 8% for Interventional Therapies, and 50% for Galileo. Lesion length, minimal lumen diameter, renal failure, diabetes, and smoking did not predict treatment failure; only age was inversely correlated with MACE (P=.002).

CONCLUSION

When applied across a spectrum of patients, lesions, and devices, brachytherapy retains its effectiveness with outcomes similar to those reported in randomized clinical trials.

Catheter based intracoronary brachytherapy leads to increased platelet activation

BACKGROUND

Vascular brachytherapy (VBT) after percutaneous coronary intervention (PCI) is associated with a higher risk of stent thrombosis than conventional treatment.

OBJECTIVE

To investigate in vivo periprocedural platelet activation with and without VBT, and to assess a possible direct effect of radiation on platelet activation.

DESIGN

Of 50 patients with stable angina, 23 received VBT after PCI, while 27 had PCI only. The 23 patients who received VBT after PCI were pretreated for one month with aspirin and clopidogrel. Platelet activation was assessed by flow cytometry.

RESULTS

The two patient groups did not differ in their platelet activation before the intervention. There was a significant increase in activation immediately after VBT, with 21.2% (interquartile range 13.0% to 37.6%) thrombospondin positive and 54.0% (42.3% to 63.6%) CD 63 positive platelets compared with 12.7% (9.8% to 14.9%) thrombospondin positive and 37.9% (33.2% to 45.2%) CD 63 positive platelets before the intervention (p < 0.001 and p < 0.01, respectively). Patients without VBT had no periprocedural difference in platelet activation immediately after PCI. No increase in platelet activation was found after ex vivo irradiation of blood samples obtained from healthy controls.

CONCLUSIONS

Catheter based intracoronary VBT carried out according to current standards is highly thrombogenic. The current antithrombotic treatment with aspirin and clopidogrel is not sufficient to suppress platelet activation during the procedure. From in vitro experiments, it appears that platelet activation during brachytherapy is not caused by irradiation but by the procedure of catheter based VBT.

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.

Impact of radiation dose on late clinical outcome after intracoronary radiation therapy: Three-year follow-up of Long WRIST

To determine the safety and efficacy, including the impact, on the late recurrence rate of an incremental gamma-radiation dose from 15 to 18 Gy, we report the 3-year clinical outcome of Washington Radiation for In-Stent Restenosis Trial for Long Lesions (Long WRIST). One hundred eighty patients with recurrent in-stent restenosis (ISR) were enrolled in the Long WRIST series and treated with (192)Ir with 1 month of antiplatelet therapy. Between 6 months and 3 years, the need for repeat revascularization was low and similar among the three groups. At 3 years, target lesion revascularization (TLR) and major adverse cardiac events (MACE) were less frequent in the 18 Gy group than in the 15 Gy group (P = 0.12 for TLR, P < 0.05 for MACE) and less frequent in the 15 Gy group as compared to the placebo group (P < 0.05 for TLR and MACE). At 3 years, a higher dose of 18 Gy with (192)Ir continues to improve the outcome of patients treated for ISR when compared to patients treated with 15 Gy or placebo.

Hemodialysis vascular access dysfunction: from pathophysiology to novel therapies

Hemodialysis vascular access dysfunction is a major cause of morbidity and hospitalization in the hemodialysis population at a cost of over USD 1 billion per annum. Most hemodialysis grafts fail due to a venous stenosis (venous neointimal hyperplasia) which then results in thrombosis of the graft. Despite the magnitude of the clinical problem there are currently no effective therapies for this condition. The current review (a) describes the pathogenesis and pathology of venous stenosis in dialysis access grafts and (b) discusses the development and application of novel therapeutic interventions for this difficult clinical problem. Special emphasis is laid on the fact that PTFE dialysis access grafts could be the ideal clinical model for testing out novel local therapies to block neointimal hyperplasia.

Vascular brachytherapy using a beta emitter source in diabetic patients with in-stent restenosis: angiographic and clinical outcomes

PURPOSE

The management of diabetic patients with restenosis after percutaneous coronary intervention remains a significant challenge. Diabetic patients remain at significant risk of restenosis despite stent implantation. This retrospective analysis was performed to determine the extent to which vascular brachytherapy improves late clinical and angiographic outcomes in diabetic patients compared to conventional therapy and compared to patients' nondiabetic counterparts.

METHODS

Pooled data from two studies (START [Stents and Radiation Trial] and START-40 trials) of patients (204 diabetic, 477 nondiabetic) receiving vascular brachytherapy (VBT) with a (90)Sr/(90)Y source after conventional percutaneous coronary intervention for in-stent restenosis comprise the study population. The radiation delivery system used in both studies was the Beta-Cath system. The prescribed dose at 2 mm from the centerline of the source axis was 18.4 Gy or 23 Gy, depending on vessel diameter. The reference vessel diameter, minimal lumen diameter, and percent diameter stenosis were measured before the intervention, at the conclusion of the procedure, and at the 8-month follow-up examination. The Breslow-Day test was used to formally assess the similarity of treatment effect between diabetic and nondiabetic patients.

RESULTS

Target lesion and target vessel revascularization rates and angiographic restenosis rates in diabetic and nondiabetic patients treated with beta radiation or placebo were analyzed. Diabetic patients were more likely to have longer and more complex coronary lesions. In-hospital outcomes in diabetic and nondiabetic patients were similar, irrespective of treatment status. At 8 months, patients treated with beta radiation exhibited less target lesion revascularization (diabetic: 10.9% vs. 22.7%, p = 0.02; nondiabetic: 12.8% vs. 22.3%, p = 0.007) and less target vessel revascularization (diabetic: 14.7% vs. 25.3%, p = 0.06; nondiabetic: 16.6% vs. 23.6%, p = 0.06) compared to placebo. In-stent binary angiographic restenosis was lower in irradiated patients (diabetic: 19.4% vs. 37.3% for placebo, p = 0.01; nondiabetic: 12.9% vs. 43% for placebo, p < 0.001). However, restenosis beyond the stent site reduced the impact of VBT, regardless of diabetic status. The magnitude of the treatment effect for target lesion and target vessel revascularization rates was similar between diabetic and nondiabetic patients.

CONCLUSIONS

Previously published institutional experiences have suggested that diabetic patients benefit from the use of VBT in the management of in-stent restenosis. This analysis now provides direct evidence to support the role of beta radiation VBT in this patient population. Diabetic patients undergoing this therapy are just as likely to benefit from it as their nondiabetic counterparts.

Current status of intravascular stents as delivery devices to prevent restenosis

The acute technical success of percutaneous transluminal angioplasty (PTA) has been improved with the use of intravascular stents. However, stent placement has led to the development of an increased myointimal hyperplastic response leading to late reduction in vessel lumen. Restenosis (> or =50% reduction in reference lumen diameter) rates for coronary angioplasty and stenting are reported between 20% and 50% at 1 year. Several studies are currently evaluating novel delivery of antiproliferative agents to prevent neointimal hyperplasia. The authors review the mechanism of neointimal hyperplasia as it relates to stent placement and discuss recent and ongoing trials evaluating intravascular brachytherapy and drug-eluting stent technology in the inhibition of restenotic lesions.

Intravascular brachytherapy: a review of the current vascular biology

Restenosis is a major limitation of coronary angioplasty, requiring further intervention in the majority of cases. Intracoronary radiation has been employed in recent years to prevent restenosis lesions with effective results, principally in in-stent restenosis. Restenosis is generally considered as an excessive form of normal wound healing divided up in processes: elastic recoil, neointimal hyperplasia, and negative vascular remodeling. Restenosis has previously been regarded as a proliferative process in which neointimal thickening, mediated by a cascade of inflammatory mediators and other factors, is the key factor. Data from recent studies have pointed to negative vascular remodeling as a major contributing factor. Recent studies have also identified particular cell lines that might be critical regulators of restenosis, particularly monocyte-derived macrophages and myofibroblasts. This review summarizes the current theories of vascular biology pertaining to restenosis in coronary arteries and the potential mechanisms of why radiation may effectively inhibit restenosis.

Intracoronary radiation therapy improves the clinical and angiographic outcomes of diffuse in-stent restenotic lesions: results of the Washington Radiation for In-Stent Restenosis Trial for Long Lesions (Long WRIST) Studies

BACKGROUND

The Washington Radiation for In-Stent Restenosis Trial for long lesions (Long WRIST) was designed to determine the safety and efficacy of vascular brachytherapy for the treatment of diffuse in-stent restenosis.

METHODS AND RESULTS

A total of 120 patients with diffuse in-stent restenosis in native coronary arteries (lesion length, 36 to 80 mm) were randomized for either radiation with 192Ir with 15 Gy at 2 mm from the source axis or placebo. After enrollment, 120 additional patients with the same inclusion criteria were treated with 192Ir with 18 Gy and included in the Long WRIST High Dose registry. Antiplatelet therapy was initially prescribed for 1 month and was extended to 6 months in the last 60 patients of the Long WRIST High Dose registry. At 6 months, the binary angiographic restenosis rate was 73%, 45%, and 38% in the placebo, 15 Gy, and 18 Gy radiated groups, respectively (P<0.05). At 1 year, the primary clinical end point of major cardiac events was 63% in the placebo group and 42% in the radiated group with 15 Gy (P<0.05). The major cardiac event rate was further reduced with 18 Gy (22%; P<0.05 versus 15 Gy). Late thrombosis was 12%, 15%, and 9% in the placebo group, 15 Gy group with 1 month of antiplatelet therapy, and 18 Gy group with 6 months of antiplatelet therapy, respectively.

CONCLUSIONS

Vascular brachytherapy with 192Ir is safe and reduces the rate of recurrent restenosis in diffuse in-stent restenosis. The efficacy of vascular brachytherapy on angiographic and clinical outcomes is enhanced with a radiation dose of 18 Gy and prolonged antiplatelet therapy.

[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.

Intravascular brachytherapy: a systematic review of its role in reducing restenosis after endovascular treatment in peripheral arterial disease

INTRODUCTION

Intravascular brachytherapy (IVBT) utilises the percutaneous insertion of a radioactive source to inhibit myointimal hyperplasia in arteries treated by balloon angioplasty or stenting. A systematic review was performed of trials of IVBT in patients with Peripheral Arterial Disease (PAD).

METHODS

Search strategy - the reviewers searched Medline, Embase, the Cochrane Peripheral Vascular Diseases Group trials register, DARE, CCT and NHS EED for clinical studies and trials of adjuvant IVBT in PAD. Two reviewers assessed trial quality independently.

RESULTS

Fourteen clinical trials were identified by the search, representing five clinical studies (all allocated D for not randomised) and one randomised controlled trial (allocated A). The randomised trial showed a benefit for IVBT compared with placebo (OR 0.35, 95% CI 0.24-0.53). In the non-randomised studies, 12 month cumulative patency rates ranged from 60-87%. There were few technical complications. In the only report involving IVBT and routine concurrent stent insertion acute thrombosis occurred in 7 (21%) of patients.

CONCLUSION

Early reports have confirmed the safety and technical feasibility of IVBT. However, follow-up is too short at present to assess the durability and long-term complications of this new therapeutic option.

How to fix the edge effect of catheter-based radiation therapy in stented arteries

BACKGROUND

Edge stenosis remains a serious limitation of catheter-based vascular brachytherapy (VBT). This study aims to identify the mechanisms and evaluate strategies to minimize edge restenosis in patients treated with VBT.

METHODS AND RESULTS

Thirty-four porcine stented coronary arteries were irradiated (doses of 15 or 22 Gy) with (192)Ir trains of either 6 seeds (23 mm) with 0 mm coverage at the distal stent edge and 10 mm at the proximal stent edge or 14 seeds (55 mm) centered at the distal edge of the stent with 27.5 and 14.5 mm coverage at the distal and proximal edges, respectively. After VBT, an additional 13-mm stent was positioned overlapping the distal margin of the first stent. Animals were killed at 28 days, and arteries were analyzed. Longer radiation margins were associated with reduced intimal area (IA) at the stent edge: 2.3+/-0.9, 3.6+/-2.0, and 5.3+/-2.2 mm(2) with 15 Gy for a radiation margin of 14.5, 10, and -13 mm (-13 versus 10, P=0.06; 10 versus 14.5, P=0.06). Additional stenting was associated with an increase of IA: 4.0+/-2.3 mm(2) at the overlapped segment. Increasing the dose to 22 Gy resulted in a reduction of the IA at the overlap segment to 1.31+/-0.57 mm(2) with 14 seeds (27.5 mm coverage) but was not helpful with 6 seeds (0 mm coverage): IA, 5.56+/-2.28 mm(2).

CONCLUSIONS

Extending the radiation margins to 14.5 mm from each end of the stent minimized the edge-effect phenomenon. A higher dose is essential to eliminate further increases in IA at the overlapped segment with additional stents.

Interventional nuclear medicine in the prevention of restenosis following angioplasty

Restenosis is an unsolved clinical and economic limitation of angioplasty. Local irradiation is a new concept to overcome this problem. The magnitude of this health problem becomes apparent when one recognizes that 166132 percutaneous transluminal coronary angioplasty (PTCA) procedures were performed in Germany in 1999. Each angioplasty has subsequent costs of 6384 DM, which can be reduced to 2161 DM by 50% restenosis reduction due to irradiation [1]. The number of diagnostic and therapeutic procedures is growing by at least 10% per year.

Cost-effectiveness of gamma radiation for treatment of in-stent restenosis: results from the Gamma-1 trial

BACKGROUND

Recently, several randomized trials have demonstrated that intracoronary brachytherapy can reduce the rates of both angiographic and clinical restenosis in patients undergoing percutaneous coronary intervention (PCI) for in-stent restenosis. Whether this practice is cost-effective is unknown.

METHODS AND RESULTS

Between December 1997 and July 1998, 252 patients with in-stent restenosis were randomized to receive brachytherapy or placebo after successful PCI as part of the Gamma-1 trial. We collected detailed resource utilization and cost data for each patient's initial hospitalization and for 1 year after randomization. Compared with conventional treatment, intracoronary brachytherapy increased procedure duration, physician services, and equipment costs. As a result, initial costs were increased by nearly $4100 per patient ($15 724 versus $11 675, P<0.001). Over the 1-year follow-up period, brachytherapy reduced the need for repeat revascularization by 21% and reduced the need for bypass surgery by 44%. Although follow-up medical care costs were $2200/patient lower with brachytherapy, total costs remained higher at 1 year ($28 543 versus $26 737, P=0.46). In a sensitivity analysis that incorporated recent technical modifications and the use of prolonged antiplatelet therapy to prevent late thrombotic occlusion, follow-up cost savings increased to $3600/patient, and 1-year costs were slightly lower with brachytherapy ($26 352 versus $26 729, P=0.87). Subgroup analysis demonstrated significant cost savings in patients with diabetes and patients who did not undergo repeat stenting.

CONCLUSIONS

As performed in the Gamma-1 trial, coronary brachytherapy for in-stent restenosis improved clinical outcomes but increased 1-year costs compared with standard therapy. If late thrombosis can be eliminated, however, this technology has the potential to reduce overall medical care costs.

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.

Hemodialysis vascular access dysfunction from basic biology to clinical intervention

Hemodialysis vascular access dysfunction is a major cause of morbidity and hospitalization in the hemodialysis population at a cost of over 1 billion dollars per annum. Venous stenosis and thrombosis as a result of venous neointimal hyperplasia are the major causes of hemodialysis vascular access dysfunction. Despite the magnitude of the clinical problem, there are currently no effective therapies for this condition. We believe that this could be because of an inadequate understanding of the pathogenesis of this condition. At a histological level, venous neointimal hyperplasia (both in human specimens and in a pig model) is characterized by the presence of smooth muscle cells/myofibroblasts, microvessel formation (angiogenesis), and the accumulation of extracellular matrix components, all of which could be potential targets for therapeutic intervention. In particular, polytetrafluoroethylene dialysis access grafts could be the ideal clinical model for testing out novel local therapies to block neointimal hyperplasia. The current review describes the lesion of venous neointimal hyperplasia in human samples and in a pig model and suggests possible future directions for the development of effective local therapies for this condition.

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

PURPOSE

To evaluate the safety and efficacy of a 40-mm 90Strontium/90Yttrium source train in the management of in-stent restenosis within native coronary arteries.

MATERIALS AND METHODS

This multicenter, prospective registry was designed to compare the results of patients with in-stent restenosis treated with a 40-mm source train to the placebo arm of the previously reported randomized Stents and Radiation Trial (START). All patients entered in the registry were treated with repeat balloon angioplasty followed by intravascular brachytherapy. Radiation dose was prescribed based on vessel size. 18 Gy was delivered at 2 mm for vessel diameters between 2.75 and 3.35 mm, and 23 Gy was used for vessels between 3.36 and 4.0 mm. The efficacy endpoints for the START 40 registry included a reduction in the target lesion revascularization (TLR) rate, target vessel revascularization rates, and target vessel failure (TVF) at 8 months. Secondary angiographic efficacy endpoints were binary restenosis at 8 months, in-stent minimum luminal diameter (MLD), and late loss. The safety endpoints included major adverse cardiac events as well as late aneurysm formation. The registry was designed to allow a statistically valid comparison of these results to the placebo group of the START 30 trial. Quantitative angiographic analysis was performed on the 8-month follow-up examination. Rates of restenosis were evaluated for various segments of the treated vessel. A separate analysis was performed to evaluate the relationship between vessel injury length and the radiated segment.

RESULTS

A total of 207 patients were entered into the START 40 registry. The postprocedure angiographic results, including the postprocedure MLD and percent diameter stenosis, were similar between the START 40 patients and the placebo group from the START trial in the stented segment of the treated vessel. Eight-month angiographic follow-up was available on 150 patients from the registry. The TLR rate was significantly reduced when compared to the placebo group (11% vs. 22.4% respectively, p = 0.008). A similar reduction was seen in terms of target vessel revascularization (15.9% vs. 24.1%, p = 0.03). The 8-month MLD was found to be significantly larger in the START 40 patients (1.85 mm vs. 1.47 mm, p < 0.0001). The difference seen in the clinical endpoint of TVF (19.3% vs. 25.9%) did not reach statistical significance (p = 0.1). Analysis of the procedural angiograms revealed mismatch between the length of vessel injured and the location of the 90% isodose in 46% of the treated cases. Angiographic analysis revealed that geographic miss was associated with a higher rate of binary restenosis (32% vs. 18% p = 0.04) in the analysis segment.

CONCLUSIONS

This multicenter registry demonstrates the safety and efficacy of a 40-mm 90Strontium/90Yttrium source train in the management of patients with in-stent restenosis. Restenosis rates were lowered with the use of this longer source train when compared to the placebo arm of the START trial for lesions with a maximum vessel injury length of 20 mm. Angiographic analysis identified the importance of the accurate delineation of injury length and correct source positioning. These results support the continued use of beta radiation for the treatment of this disease process.

Intravascular brachytherapy for peripheral vascular disease

BACKGROUND

International treatment of atherosclerotic narrowed and blocked arteries involves either bypassing the blockage using a graft, widening it from the inside with a balloon, a procedure known as percutaneous transluminal angioplasty (PTA), or providing a strut to hold the vessel open, known as a stent. All of these treatments are however limited by the high numbers that fail within a year. Intravascular brachytherapy (IVBT) is the application of radiation directly to the site of vessel narrowing. It is known to inhibit the processes that lead to restenosis (narrowing) of vessels and grafts after treatment.

OBJECTIVES

The objective of this review was to assess the efficacy and complications of intravascular brachytherapy on maintaining patency after angioplasty or stent insertion in native vessels or bypass grafts of the iliac or infrainguinal arteries.

SEARCH STRATEGY

The reviewers searched the Cochrane Peripheral Vascular Diseases Group Trials Register (last searched 5 July 2002), the Cochrane Controlled Trials Register (last searched Issue 2, 2002), MEDLINE, EMBASE and reference lists of relevant articles.

SELECTION CRITERIA

Randomised trials of the use of brachytherapy as an adjunct to the treatment of patients with peripheral arterial diseases (PAD) or stenosed bypass grafts of the iliac or infrainguinal arteries arteries versus the procedure without brachytherapy.

DATA COLLECTION AND ANALYSIS

Two reviewers independently assessed trial quality and extracted data. Adverse events information was collected from the trials.

MAIN RESULTS

One trial was identified which met the inclusion criteria, involving 117 patients, mean age 71 years (43-89). The trial compared PTA versus PTA and IVBT in patients with long-segment de novo or restenotic lesions or occlusions of any length in the femoropopliteal artery. Results were provided at six month follow up in 107 patients (54 PTA alone, 53 PTA+IVBT). The results favoured adjuvant IVBT in preventing restenosis/occlusion with an odds ratio (OR) of 0.35 (95% CI 0.24 to 0.53). Analysis of subgroups showed a significant benefit of IVBT in non-diabetics, OR 0.22 (95% CI 0.07 to 0.69), in those undergoing IVBT in restenotic lesions, OR 0.32 (95% CI 0.10 to 1.01), occlusive lesions, OR 0.19 (95% CI 0.06 to 0.62) and lesions in which the PTA length was greater than 10cm, OR 0.24 (95% CI 0.09 to 0.62).

REVIEWER'S CONCLUSIONS

Results from the only trial available would suggest that IVBT is effective at improving the patency of femoropopliteal arteries undergoing PTA in the short-term, particularly in non-diabetics with long occlusions (>10cm).

Targeting the adventitia with intracoronary beta-radiation: comparison of two dose prescriptions and the role of centering coronary arteries

PURPOSE

To compare by intravascular ultrasound (IVUS) the efficacy of delivering the prescribed dose to the adventitia between two commonly used dose prescriptions for intracoronary radiotherapy.

METHODS AND MATERIALS

In 59 human postangioplasty coronary vessels, one IVUS cross-section (1 mm thick) with the highest plaque burden was used for creating dose-volume histograms with different hypothetical positions of the source.

RESULTS

On average, prescription to 1 mm beyond lumen surface resulted in delivery of the prescribed dose (20 Gy +/- 20%) to a higher fraction of adventitial volume than with the prescription to 2 mm from the source, with source placed in vessel center, lumen center, or in the IVUS catheter position. Source placement in the lumen center resulted in a low dose heterogeneity to the adventitia and the least dose heterogeneity to the intima.

CONCLUSIONS

Prescription to 1 mm beyond lumen surface appeared more effective in delivering the prescribed dose to the adventitia than the American Association of Physicists in Medicine (AAPM) recommended prescription to 2 mm from the source center. Moreover, centering the source in the lumen provides the better balance of effective adventitial targeting and intimal dose homogeneity. Modification of the current AAPM recommendation for dose prescription for intracoronary radiotherapy should be considered.

Intracoronary beta-radiation exacerbates long-term neointima formation in balloon-injured pig coronary arteries

BACKGROUND

Long-term biological effects of ionizing radiation on coronary arteries remain poorly defined. We examined late arterial responses 6 months after balloon angioplasty and beta-radiation in normal pig coronary arteries.

METHODS AND RESULTS

Coronary arteries of 25 adult pigs were randomized to receive 20 Gy (n=8) or 30 Gy (n=9) of (186)Re beta-radiation or sham radiation (n=8) immediately after balloon angioplasty. Aspirin was given daily during follow-up. The study vessels were analyzed histopathologically at 6 months. beta-Radiation decreased lumen area (20 Gy, 1.55+/-0.99 mm(2); 30 Gy, 1.03+/-0.82 mm(2); and 0 Gy, 2.05+/-0.80 mm(2); P<0.05) but not overall vessel area. The neointimal area was significantly larger within the injured segment with beta-radiation (20 Gy, 1.92+/-1.23 mm(2); 30 Gy, 1.51+/-0.97 mm(2); and 0 Gy, 0.89+/-0.31 mm(2); 0 Gy versus 20 Gy, P<0.05), and a significant increase of edge stenosis was observed with beta-radiation. Irradiated vessels also had larger thrombus areas within the neointima (30 Gy, 0.24+/-0.61 mm(2); 20 Gy, 0.98+/-1.57 mm2; and 0 Gy, 0.00+/-0.01 mm(2); P<0.05) and larger adventitial areas (20 Gy, 2.25+/-0.75 mm(2); 30 Gy, 2.38+/-0.98 mm(2); and 0 Gy, 1.23+/-0.29 mm(2); 0 Gy versus 20 or 30 Gy, P<0.05) that showed substantial collagen accumulation.

CONCLUSIONS

Intracoronary beta-radiation did not inhibit neointima formation in balloon-injured normal pig coronary arteries 6 months after the interventional procedure. Unresorbed thrombus contributed to, but was not the sole component of, augmented neointima formation. Irradiated vessels demonstrated more adventitial thickening and fibrosis. These observations may have relevance for long-term clinical outcomes after intracoronary beta-radiation.

Dose-response study of intracoronary beta-radiation with 32P in balloon- and stent-injured coronary arteries in swine

PURPOSE

A dose-response study was performed in swine to investigate the vascular effects of 32P over a broad range of doses in order to define the therapeutic window of intracoronary radiotherapy (ICR) with 32P.

METHODS AND MATERIALS

A total of 131 porcine arteries were subjected to balloon injury or stenting followed by 0-36 Gy of ICR from a centered 32P source wire to 1 mm beyond lumen surface or a sham ICR procedure. Animals were euthanized at 4 weeks, and vessels were harvested for histomorphometry.

RESULTS

In the balloon-injured arteries, doses of 7 and 9 Gy did not impact restenosis. At doses of 14-36 Gy, neointima was markedly reduced, with mild dilatation at the highest dose, 36 Gy. In the stent-injured arteries, the lowest dose of 9 Gy failed to reduce neointimal growth, while 14-26 Gy showed the most favorable response.

CONCLUSIONS

ICR with 32P features a broad therapeutic window. Doses of 14-26 Gy to 1 mm beyond lumen surface provided an optimal combination of efficacy and safety. Doses of 7 and 9 Gy were generally ineffective, suggesting a minimum threshold for ICR with 32P to effectively inhibit restenosis.