Debulking does not benefit patients undergoing intracoronary beta-radiation therapy for in-stent restenosis: insights from the START trial

Current understanding of coronary in-stent restenosis. Pathophysiology, clinical presentation, diagnostic work-up, and management

In-stent restenosis is the limiting entity following coronary stent implantation. It is associated with significant morbidity and cost and thus represents a major clinical and economical problem. Worldwide, approximately 250 000 in-stent restenotic lesions per year have to be dealt with. The pathophysiology of instent restenosis is multifactorial and comprises inflammation, smooth muscle cell migration and proliferation and extracellular matrix formation, all mediated by distinct molecular pathways. Instent restenosis has been recognised as very difficult to manage, with a repeat restenosis rate of 50% regardless of the mechanical angioplasty device used. Much more favourable results were reported for the adjunctive irradiation of the in-stent restenotic lesion, with a consistent reduction of the incidence of repeat in-stent restenosis by 50%. Data from the first clinical trials on drug-eluting stents for the treatment of in-stent restenosis have shown very much promise yielding this strategy likely to become the treatment of choice. This review outlines the histological and molecular findings of the pathophysiology, the epidemiology, the predictors and the diagnostic work-up of in-stent restenosis and puts emphasis on the various treatment options for its prevention and therapy.

Comparison of angiographic and clinical outcomes between rotational atherectomy and cutting balloon angioplasty followed by radiation therapy with a rhenium 188-mercaptoacetyltriglycine-filled balloon in the treatment of diffuse in-stent restenosis

BACKGROUND

Rotational atherectomy (RA) and cutting balloon angioplasty (CBA) have been shown to effectively dilate in-stent restenosis (ISR). It is not known, however, which of these technique, when followed by beta-radiation, is more effective. Therefore, we performed a prospective randomized study comparing RA and CBA before beta-radiation therapy for diffuse ISR.

METHODS

Patients with diffuse ISR were randomly assigned to receive RA (group 1, n = 58) or CBA (group 2, n = 55) before beta-radiation therapy with a rhenium 188-mercaptoacetyltriglycine-filled balloon, with the radiation dose being 18 Gy at a depth of 1.0 mm into the vessel wall. The primary end point was angiographic restenosis at 6 months, and the secondary end point was major adverse cardiac events (myocardial infarction, death, target lesion revascularization) at 9 months.

RESULTS

The 2 groups were similar in baseline characteristics. Mean lesion length was 21.0 +/- 11.2 mm in group 1 and 20.8 +/- 10.2 mm in group 2 (P = .77). Radiation was delivered successfully to all patients. We obtained 6-month angiographic follow-up in 90 patients (80%). The rates of angiographic restenosis were 14.9% (7 of 47) in group 1 and 14.0% (6 of 43) in group 2 (P = .89). No patient experienced myocardial infarction or death during the 9-month follow-up period. Rates of target lesion revascularization or major adverse cardiac events were 3.4% in group 1 and 3.6% in group 2 (P = .94) during the 9-month follow-up.

CONCLUSIONS

Either RA or CBA, followed by beta-radiation using a rhenium 188-mercaptoacetyltriglycine-filled balloon, is equally safe and effective for diffuse ISR in 6-month angiographic and 9-month clinical outcomes.

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.

Comparison of angiographic and clinical outcomes between rotational atherectomy versus balloon angioplasty followed by radiation therapy with a rhenium-188-mercaptoacetyltriglycine-filled balloon in the treatment of diffuse in-stent restenosis

BACKGROUND

The purpose of this study was to compare the efficacy of rotational atherectomy (RA) with simple balloon angioplasty, prior to beta-radiation therapy with a rhenium-188-mercaptoacetyltriglycine (188Re-MAG3)-filled balloon for diffuse in-stent restenosis (ISR).

METHODS

After completing 50 cases with RA prior to beta-radiation (Group I), we performed optimal balloon angioplasty followed by beta-radiation in the next 53 consecutive patients (Group II) for the treatment of diffuse ISR. The radiation dose was 15 Gy at a depth of 1.0 mm into the vessel wall.

RESULTS

The baseline clinical and angiographic characteristics were similar between the two groups. The mean length of the lesion was 25.6+/-12.7 mm in Group I and 22.9+/-8.6 mm in Group II (p=0.26). Radiation was successfully delivered to all patients, with a mean irradiation time of 179+/-55 s. The 6-month angiographic restenosis rate was 10% (5/50) in Group I versus 33% (17/51) in Group II (p=0.007). No adverse event including myocardial infarction, death, or stent thrombosis occurred during the 1-year follow-up period. The risk of a target lesion revascularization or a major adverse cardiac event was significantly lower in Group I than in Group II (two patients in Group I vs. nine patients in Group II; OR, 0.20; 95% CI, 0.04-0.96; p=0.04).

CONCLUSION

Concomitant treatment with rotational atherectomy and beta-irradiation using a 188Re-MAG3-filled balloon for diffuse ISR has a synergistic effect, in terms of 6-month angiographic restenosis and 1-year cardiac event-free survival.

Brachytherapy for restenosis after stenting for coronary artery disease: its role in the drug-eluting stent era

PURPOSE OF REVIEW

Recent years have brought remarkable changes to the field of interventional cardiology. The need for repeat intervention due to restenosis, the most vexing long-term failure of percutaneous coronary intervention, has been significantly reduced owing to the introduction of two major advances, the vascular brachytherapy (VBT) and the drug-eluting stents (DES).

RECENT FINDINGS

Vascular brachytherapy has demonstrated its efficacy in limiting recurrence of existing in-stent restenosis. The past 2 years have sealed its reputation, with a variety of studies demonstrating its superiority over conventional therapy in challenging patient subsets with high risk for restenosis recurrence. Moreover, the long-term follow-up confirmed durability of this therapy, and the failures of VBT were characterized as easy to treat. Conversely, DES have shown spectacular efficacy at primarily preventing the first restenosis episode following the initial stent placement. Consequently, the role of VBT may be minimized, as the overall need for repeat revascularization is diminished as a result of the wide acceptance of DES. Furthermore, if the capacity of DES to treat in-stent restenosis is confirmed in randomized trials, they may eventually supersede VBT as the therapy of choice for in-stent restenosis.

SUMMARY

At present, VBT is the proven and durable therapeutic choice for patients with complex, diffuse in-stent restenosis who would otherwise have a very poor prognosis for long-term event-free survival. DES have emerged as remarkably effective in minimizing the first restenosis occurrence; they also represent a promising and competitive alternative to VBT for the treatment of in-stent restenosis.

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.

Vascular restenosis - striving for therapy

Restenosis is the limiting entity following coronary angioplasty. It is associated with significant morbidity, mortality and cost, and thus represents a major clinical and economical problem. Despite technical improvements, restenosis after conventional balloon angioplasty occurs in 30 - 60% of cases. Coronary stenting was able to reduce the incidence by approximately 30%; nevertheless, some 250,000 patients experience in-stent restenotic lesions/year worldwide. In-stent restenosis has been recognised as very difficult to manage, with a repeat restenosis rate of 50%, regardless of the angioplasty device used. So far, only vascular brachytherapy has convincingly reduced the incidence of repeat in-stent restenosis (by 50%) and thus, has emerged as the gold standard of therapy. The introduction of drug-eluting stents has shown a great deal of promise for the treatment of both de novo and restenotic lesions, with reported restenosis rates of < 10%, and benefit for virtually all patient subsets at a higher risk of restenosis. This review outlines the pathophysiology, epidemiology and predictors of the restenosis process, and places emphasis on the various treatment options for its prevention and therapy.