How long is enough? Defining the treatment length in endovascular brachytherapy

Two-year clinical follow-up results of intracoronary radiation therapy with rhenium-188-diethylene triamine penta-acetic acid-filled balloon

We investigated the 2-year clinical follow-up results as well as 6-month angiographic and clinical follow-up results of intracoronary radiation therapy using a rhenium-188-diethylene triamine penta-acetic acid ((188)Re-DTPA)-filled balloon system. The study comprised of 161 patients with significant de novo (83%) or in-stent restenosis (17%) lesions. Irradiation to deliver 17.6 Gy at a depth of 1.0 mm into the vessel wall was carried out after successful intervention. At 6-month follow-up, binary restenosis developed with significantly lower frequency in the radiation group than in the control group (24.3% vs. 46.3%; P = 0.009), although target lesion revascularization rate did not show significant benefit. At 2-year follow-up, cumulative target lesion revascularization rate was not significantly different between radiation group (n = 86) and control group (n = 75; 20.0% vs. 26.0%; P = 0.368). The rate of major adverse cardiac events including death, myocardial infarction, and target lesion revascularization did not show significant difference between two groups either (22.3% vs. 30.1%; P = 0.266). In conclusion, although significant reduction in restenosis rate was noted at 6-month angiographic follow-up, intracoronary radiation therapy mostly in patients with de novo lesion did not show significant clinical benefit in 6-month and 2-year follow-up results. The benefit was noted only in a small subgroup of patients with in-stent restenosis.

Direct Stenting Versus Direct Stenting Followed by Centered Beta-Radiation With Intravascular Ultrasound-Guided Dosimetry and Long-Term Anti-Platelet Treatment

OBJECTIVES

We sought to assess the efficacy of vascular brachytherapy (VBT) combined with stenting for the primary prevention of restenosis.

BACKGROUND

Intravascular brachytherapy after stent implantation for de novo lesions has been abandoned for the present. We revisited this procedure by optimizing all procedural steps-the use of glycoprotein IIb/IIa blockers, direct stenting, adequate radiation coverage, avoidance of edge damage, source centering, intravascular ultrasound-guided dosimetry, and continuation of a dual anti-platelet regimen for one year.

METHODS

The Beta-Radiation Investigation with Direct stenting and Galileo in Europe (BRIDGE) study is a multicenter, randomized controlled trial evaluating the long-term efficacy of VBT with P-32 (20 Gy at 1 mm in the coronary wall) after direct stenting. The primary end point was angiographic intra-stent late loss; secondary end points were six months binary restenosis and neo-intimal hyperplasia. Patients (n = 112) with de novo lesions (2.5 to 4.0 mm in diameter up to 15 mm long) were randomized to either VBT or no-VBT.

RESULTS

At six months, intra-stent loss was 0.43 and 0.84 mm (p < 0.001) in the irradiated and control groups, respectively. Intra-stent neo-intimal volume was reduced from 36 mm3 to 10 mm3. However, in the irradiated group there were six late occlusions as well as eight restenoses outside the stented and peri-stented area at the fall-off dose edges of the irradiated area. Accordingly, the target vessel revascularization and major adverse cardiac and cerebrovascular events rates at one year in the VBT group (20.4% and 25.9%, respectively) were higher than in the control group (12.1% and 17.2%, respectively).

CONCLUSIONS

Despite the optimization of pre-, peri-, and post-procedural factors and despite the relative efficacy of the brachytherapy for the prevention of the intra-stent neo-intimal hyperplasia, the clinical outcome of the irradiated group was less favorable than that of the control group.

Quality assurance in intracoronary brachytherapy. Recommendations for determining the planning target length to avoid geographic miss

BACKGROUND AND PURPOSE

A new method of assessing geographic miss (GM) in endovascular brachytherapy (EVBT) is applied to evaluate the quality of intracoronary brachytherapy treatments, retrospectively. Based on the Vienna experience, recommendations for adequate safety margins are derived to avoid GM.

PATIENTS AND METHODS

Evaluation is done on 136 vessels of 128 consecutive patients treated between October 1999 and July 2001. The quality of EVBT is assessed using the concept and terminology of the EVA GEC ESTRO task group. Evaluation of GM and/or safety margin is performed by comparing the outermost interventions with the reference isodose length (RIL) of the applied delivering devices on recorded compact disk (CD) angiograms. The RIL is defined as the length of the vessel segment, which receives at least 90% of the reference dose at the reference depth (=1 mm within the vessel). GM is defined as injured vessel segments, which receive a dose lower than 90% of reference dose. Measurements of intervention length (IL) and active source length (ASL) are performed with respect to anatomical landmarks within the vessel in the region of interest (e.g. stent edges), and by using the nominal length of the devices (balloons, sources) as a reference scale. The edges of RIL are determined by subtracting the length of the dose-fall-off zone (specific to the applied delivery devices: (192)Ir 4.5 mm, (90)Sr 2.5 mm, (32)P 2.0 mm) from the edges of ASL.

RESULTS

The described method to assess GM is applicable to 128 vessels (94%). GM is found in 23% of proximal edges and 20% of distal edges. 95% of all GM are observed if the total margin (proximal+distal margin) between RIL and IL is shorter than 10.5 mm.

CONCLUSIONS

GM in intracoronary brachytherapy can be widely avoided by adding an appropriate safety margin to the IL (5-6 mm each edge in this study) in order to determine the necessary RIL for a treatment.

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

A novel measurement technique to assess the effects of coronary brachytherapy in clinical trials

This paper presents a novel measurement technique to assess the effects of coronary brachytherapy. This new technique is based upon the conventional quantitative coronary analysis (QCA) technique, which is accepted worldwide as an accurate and reliable analysis tool for clinical trials. This paper provides the definitions and main issues important for correct brachytherapy analysis. Based on these definitions, this novel technique is implemented as an extension of conventional QCA software, as a multisegmental analysis tool. It allows to follow the influence of radiation on restenosis, and the mutual relation between intervention devices. A pilot interobserver study was performed to assess the reliability and reproducibility of the brachytherapy analysis tool, using 15 patient cases. The validation results show that the segment lengths, minimum lumen diameter, and reference diameters of the user-defined and derived (sub)segments can be assessed reproducible. However, these good results can only be obtained, when strict and extensive image acquisition and image analysis protocols are followed. From this pilot validation study presented in this paper and only based on a small number of patients, we may conclude that the software can be applied to clinical trials.

Endovascular gamma irradiation of femoropopliteal de novo stenoses immediately after PTA: interim results of prospective randomized controlled trial

PURPOSE

To report an interim analysis of whether centered endovascular irradiation with the iridium 192 ((192)Ir) source immediately after percutaneous transluminal angioplasty (PTA) of de novo femoropopliteal stenoses lowers the restenosis rate.

MATERIALS AND METHODS

Thirty patients undergoing PTA to treat femoropopliteal stenoses were randomized for prophylaxis against restenosis with centered endovascular irradiation with a (192)Ir source (a dose of 14 Gy 2 mm deep to the vessel wall, irradiation group) or no irradiation (control group). Angiographic follow-up was available for 22 patients at 6 months (irradiation group, n = 10) and 12 patients at 12 months (irradiation group, n = 6). Duplex sonography, treadmill testing, and interviews were performed the day before and the day after PTA and after 1, 3, 6, 9, and 12 months. Results of angiography, duplex sonography, treadmill testing, and interviews were evaluated with a t test and multivariate analysis of variance (clinical characteristics, chi(2) test).

RESULTS

Baseline characteristics were comparable in the two groups. Interim analysis of the 6-month follow-up data revealed a trend toward a significantly lower restenosis rate in the irradiation group. The change in the degree of stenosis compared with that after PTA was -14.7% +/- 20.8 (mean +/- SD) in the irradiation group versus 37.7% +/- 27.3 in the control group (P =.001) and became even more marked at 12 months (-9.5% +/- 34.5 vs 45.5% +/- 40.7 [P =.03], respectively). The follow-up results of treadmill testing and interviews showed a nonsignificant benefit for the irradiation group. One thromboembolic complication occurred during irradiation. No side effects were observed during follow-up.

CONCLUSION

Endovascular irradiation with a centered (192)Ir source immediately after PTA of de novo femoropopliteal stenoses reduces the restenosis rate.

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.

Required treatment margin for coronary endovascular brachytherapy with iridium-192 seed ribbon

PURPOSE

Preliminary clinical trials (SCRIPPS I, WRIST and Gamma 1) employing catheter-based endovascular brachytherapy (EVBT) with iridium-192 (Ir-192) seeds show promising results in reducing restenosis after coronary intervention. Failure analysis of these studies showed a significant number of restenosis at the treatment margin called "edge effect." The objective of this study is to investigate the factors that contribute to the adequacy of treatment margin.

METHODS AND MATERIALS

The factors contributing to the margins are penumbra effect at the end of the seed train, uncertainty in target localization, longitudinal seed movement during cardiac cycle and barotrauma due to stent deployment. The magnitudes of the penumbra effect, which refers to the tapering off the prescribed isodose line near the ends of the source train, were calculated for various source lengths of Ir-192 seed ribbon using AAPM TG-43 algorithm. Uncertainty in target localization refers to the fact that the visual estimation of proximal and distal extent of the injury is not accurate, and this can be obtained by comparing the "estimate" from the interventional cardiologist with careful review of the cine-angiogram. Longitudinal seed movements relative to the coronary vessel during the cardiac cycle were determined by frame-by-frame reviewing cine-angiograms of 30 patients. The proximal and distal source points were measured in reference to branching vessels during the contrast phase of the cine-angiogram. The maximum proximal and distal longitudinal movement was captured and source displacement was measured from the closest proximal and distal branching vessel. Barotrauma, additional injury to the vessel arising from the stent deployment balloon, was obtained by reviewing specifications from commercially available stent delivery systems.

RESULTS

The penumbra effect ranges from 3.9 to 4.5 mm for 6-22 Ir-192 seed ribbons. The uncertainty in target localization is within 3 mm for our interventional cardiologists. The results of seed movements were categorized by three major coronary vessels and by proximal versus distal ends. The mean and standard deviation of seed movement are 1.1 and 0.8 mm, respectively. The average length of barotrauma beyond the stent margins for reviewed stents was 1.7 mm, ranging from 0.5 to 2.5 mm.

CONCLUSION

A minimum of 8-mm treatment margin is recommended for coronary vascular brachytherapy with Ir-192 seed ribbon. This was derived by considering the above contributing factors. Excessive margins should be avoided due to possible increase risk of late effect. By providing adequate treatment margins, one can avoid geographic miss; hence, one can further improve the effect of EVBT in reducing restenosis.

Prevention of restenosis with intravascular beta-radiotherapy

Beta radiation has been clearly shown, in a specific dose range, to be highly effective in the inhibition of the restenotic process after balloon or stent injury in animal experiments, as well as in randomized, placebo-controlled human trials. The major advantage of beta radiation, in comparison with gamma radiation, is a significantly lower radiation exposure to the personnel and patient, and easier adaptability to existing cardiac catheterization laboratories. Rapidly accumulating evidence indicates that the two major problems, late thrombosis and edge stenosis, may be minimized with prolonged antiplatelet therapy (6 months or more) and broader radiation coverage of the intervention site. Although there may be better, safer, and easier options to reduce restenosis in the years to come, intravascular radiotherapy is the first breakthrough modality that has been shown to significantly reduce restenosis after percutaneous vascular interventions.