Background: Although the frequency of restenosis after coronary angioplasty is reduced by stenting, when restenosis develops within a stent, the risk of subsequent restenosis is greater than 50 percent. We report on a multicenter, double-blind, randomized trial of intracoronary radiation therapy for the treatment of in-stent restenosis. Methods: Of 252 eligible patients in whom in-stent restenosis had developed, 131 were randomly assigned to receive an indwelling intracoronary ribbon containing a sealed source of iridium-192, and 121 were assigned to receive a similar-appearing nonradioactive ribbon (placebo). Results: The primary end point, a composite of death, myocardial infarction, and the need for repeated revascularization of the target lesion during nine months of follow-up, occurred in 53 patients assigned to placebo (43.8 percent) and 37 patients assigned to iridium-192 (28.2 percent, P=0.02). However, the reduction in the incidence of major adverse cardiac events was determined solely by a diminished need for revascularization of the target lesion, not by reductions in the incidence of death or myocardial infarction. Late thrombosis occurred in 5.3 percent of the iridium-192 group, as compared with 0.8 percent of the placebo group (P=0.07), resulting in more late myocardial infarctions in the iridium-192 group (9.9 percent vs. 4.1 percent, P=0.09). Late thrombosis occurred in irradiated patients only after the discontinuation of oral anti-platelet therapy (with ticlopidine or clopidogrel) and only in patients who had received new stents at the time of radiation treatment. Conclusions: Intracoronary irradiation with iridium-192 resulted in lower rates of clinical and angiographic restenosis, although it was also associated with a higher rate of late thrombosis, resulting in an increased risk of myocardial infarction. If the problem of late thrombosis within the stent can be overcome, intracoronary irradiation with iridium-192 may become a useful approach to the treatment of in-stent restenosis.
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