Current status of radioactive stents for the prevention of in-stent restenosis

Purpose: The objective of this paper was to provide an update on the clinical and experimental evaluation of radioactive stents for the prevention of restenosis. Materials and Methods: Direct ion implantation of P-32 onto the surface of a 15-mm length balloon expandable stainless-steel Palmaz-Schatz stent was employed to render this commercially available vascular stent radioactive. (32)Phosphorous, a pure beta-particle-emitting radioisotope, was selected because of its short half-life (14.3 days) and limited range of tissue penetration (3-4 mm), The vascular response to radioactive 7-mm length Palmaz-Schatz stents with activities 0.14 to 23 mu Ci of P-32 were evaluated in animal models of arterial injury and restenosis, The Phase-1 isostent for restenosis intervention study (IRIS trial) was a nonrandomized safety trial designed to evaluate the use of a low activity P-32 (0.5 to 1.5 mu Ci) 15-mm length Palmaz-Schatz stent for the treatment of de novo or restenosis native coronary arterial lesions. Results: In the porcine coronary restenosis model, at less than or equal to 0.5 mu Ci and greater than or equal to 3.0 mu Ci stent activities, there was a 30% reduction in the neointimal and percent area stenosis as compared to nonradioactive stents, The 1.0 mu Ci stents, however, had nearly 2-fold greater neointimal formation and more luminal narrowing than the control stents, In the Phase 1 IRIS trial, 57 patients with symptomatic de novo or restenosis native coronary lesions have been treated with low activity (0.5 to 1.5 mu Ci) P-32 Palmaz-Schatz coronary stents, Fifty-seven stents were successfully implanted without a major procedural complication (death, urgent coronary bypass, Q-wave myocardial infarction), There were no cases of stent thrombosis, target vessel revascularization, or other adverse events in the first 30 days after implant. Conclusion: The early clinical results with a low-activity P-32 Palmaz-Schatz radioactive stent demonstrate Sufficient procedural and 30-day event-free survival to warrant consideration of additional clinical studies to determine the safety and efficacy of this therapy for the prevention of restenosis. Future studies will focus on optimal stent design for delivery of radiation, and will further evaluate safe and effective dosing strategies. (C) 1998 Elsevier Science Inc.