Use of localised intracoronary β radiation in treatment of in-stent restenosis: the INHIBIT randomised controlled trial

Background In-stent restenosis is a major limitation of intracoronary stenting. Ionising γ radiation has been shown to reduce recurrence of restenosis after stent placement. We aimed to compare the effects of intracoronary β radiation treatment with those of placebo for clinical and angiographic outcomes of patients with diffuse in-stent restenosis. Methods 332 patients with in-stent restenosis underwent successful coronary intervention, and were then randomly allocated to intracoronary β radiation with a phosphorus-32 source (n=166) or placebo (166) delivered into a centreing balloon catheter through an automatic afterloader. Longer lesions (>22 mm of dilated length) were treated with tandem positioning of the study wire. The primary safety endpoint was major adverse cardiac events, defined as death, myocardial infarction, and repeat target-lesion revascularisation at 9 months. The primary efficacy endpoint was binary angiographic restenosis rate in the analysis segment during 9-monthsʹ follow-up. Analysis was by intention to treat. Findings Procedural success, and in-hospital and 30-day complications were similar among the two groups. 24 (15%) patients in the radiated group had the primary safety endpoint of death, myocardial infarction, or repeat targetlesion revascularisation over 290 days compared with 15 (31%) in the placebo group (difference 16% [95% CI 7–25], p=0·0006). Binary angiographic restenosis rate was lower in the radiated group than the placebo group for the entire analysed segment (difference 25% [14–37], p<0·0001). Interpretation Vascular brachytherapy using pure β-emitter 32P delivered into a centreing catheter via an automatic afterloader can be used to reduce overall revascularisation in patients undergoing treatment for diffuse in-stent restenosis.