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

Abstract

Background - Radioactive 32P β-emitting stents have been shown to reduce intrastent neointimal hyperplasia in 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 32P radioactive β-emitting stents (initially the Palmaz-Schatz and later the BX Isostent) with an activity level of 0.75 to 3.0 μCi (group 1), 3.0 to 6.0 μCi (group 2), and 6.0 to 12.0 μCi (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 32P radioactive β-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'.