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Background —The aim of this study was to use serial volumetric intravascular ultrasound to evaluate the effect of γ-radiation on recurrent in-stent restenosis. Methods and Results —After successful reintervention, patients were randomized to receive either 192 Ir or placebo. Intravascular ultrasound studies with motorized pullback (0.5 mm/s) were performed immediately after irradiation and at 8-month follow-up in 70 patients. Paired volumetric analysis of the stented segment and of 5-mm proximal and distal reference segments was performed; this included measurements of the external elastic membrane, lumen, plaque and media (external elastic membrane minus lumen), stent, and intimal hyperplasia (stent minus lumen). Baseline proximal reference, stent, and distal reference measurements were similar in both groups. The changes in proximal and distal reference measurements of the external elastic membrane, plaque and media, and lumen areas were similar in both groups. However, the decrease in stented segment lumen volume was less in the 192 Ir patients than the placebo patients (–25±34 mm 3 versus –48±42 mm 3 ; P =0.0225), and the increase in the volume of intimal hyperplasia in the stented segment was less in the 192 Ir patients than in the placebo patients (28±37 mm 3 versus 50±40 mm 3 ; P =0.0352). When averaged over the length of the stented segment (32±13 mm versus 33±14 mm; P =0.9), the increase in mean area of intimal hyperplasia was 0.8±1.0 mm 2 in the 192 Ir group and 1.6±1.2 mm 2 in the control group ( P =0.0065). Late stent-vessel wall malapposition was noted in one placebo patient and no 192 Ir patients. Conclusions —γ-Radiation therapy can effectively prevent recurrent in-stent restenosis by inhibiting neointimal formation within the stent. At the stent edge, there were no significant differences between 192 Ir and placebo patients.

Background— Although 192 Ir intracoronary brachytherapy has been demonstrated to dramatically reduce the recurrence of in-stent restenosis, up to 24% of these patients will still require repeat target-vessel revascularization. The short- and long-term outcomes of repeat percutaneous intervention in this population have not been characterized. Methods and Results— Analysis was performed of all patients enrolled in the GAMMA-I and GAMMA-II brachytherapy trials who underwent repeat percutaneous target lesion revascularization (TLR) because of restenosis. Subjects were divided into 2 cohorts: those who had received 192 Ir brachytherapy and those randomized to placebo. Forty-five (17.6%) of a total of 256 patients whose index treatment was intracoronary radiation therapy and 36 (29.8%) of 121 patients whose index treatment was placebo required repeat percutaneous TLR. The mean time to this first TLR was 295±206 days in the irradiated group and 202±167 days in the placebo group ( P =0.03). Acute procedural success occurred in 100% of irradiated patients and 94% of placebo controls ( P =0.19). After the first TLR, a subsequent TLR was required in 15 (33.3%) of 45 brachytherapy patients versus 17 (47.2%) of 36 placebo failure patients ( P =0.26). There was no significant difference in time to second TLR between the 2 groups. Other long-term major adverse event rates in both groups were comparable to those of other contemporary angioplasty/stenting series. Conclusions— In those patients who “fail” 192 Ir intracoronary brachytherapy for in-stent restenosis, treatment with 192 Ir delays the time to first TLR. Additionally, repeat percutaneous intervention in these patients is safe and efficacious in the short term, with acceptable long-term results.