Short- and intermediate-term results of 32P radioactive β-emitting stent implantation in patients with coronary artery disease -: The Milan dose-response study

Background-Radioactive P-32 beta-emitting stents have been shown to reduce intrastent neointimal hyperplasia in a substantial dose-related manner in the animal model. The aim of this dose-response study was to evaluate, in the clinical setting, the safety and efficacy at 6-month follow-up of this approach to reducing restenosis. Methods and Results-A total of 122 P-32 radioactive beta-emitting stents (initially the Palmaz-Schatz and later the BX Isostent) with an activity level of 0.75 to 3.0 mu Ci (group 1), 3.0 to 6.0 mu Ci (group 2), and 6.0 to 12.0 mu Ci (group 3) were implanted in 91 lesions in 82 patients. There were no procedural events. At 6-month follow-up, no deaths had occurred, and only 1 patient had stent thrombosis. Pure intrastent binary restenosis was 16% in group 1, 3% in group 2, and 0% in group 3. However, intralesion restenosis was 52% in group 1, 41% in group 2, and 50% in group 3. Conclusions-The use of P-32 radioactive beta-emitting stents in patients with CAD is feasible. At 6-month follow-up, intrastent neointimal hyperplasia was reduced in a dose-related manner. However, in the 3 groups, intralesion restenosis was high because of a high late lumen loss in the reference segments at the stent edges, possibly as a result of a low activity level of radiation at the edges of the stent combined with an aggressive approach to stenting. We called this "edge effect" the "candy wrapper.".