Optimizing dosimetry with high-dose intracoronary gamma radiation (21 Gy) for patients with diffuse in-stent restenosis.

Background: The efficacy of intracoronary gamma radiation (IRT-gamma) in reducing recurrent in-stent restenosis (ISR) is well established using doses of 14-18 Gy. We sought to examine whether an escalation in dose to 21 Gy is safe and confers additional benefit in reducing repeat revascularization and major adverse cardiac events (MACE) in patients with diffuse ISR.

Methods: Forty-seven patients with diffuse ISR (lesion length 20-80 mm) in native coronary arteries (n=25) and saphenous vein grafts (n=22) underwent percutaneous transluminal coronary angioplasty and/or additional stents followed by IRT-gamma using the Checkmate system (Cordis) with a dose of 21 Gy. All patients were discharged with clopidogrel for 12 months and aspirin indefinitely. Six-month angiographic and 12-month clinical outcomes of these patients were compared to 120 patients treated with 18 Gy using the same system.

Results: At baseline, patients in the 21-Gy group had more multivessel, vein graft disease and history of prior myocardial infarctions and coronary artery bypass grafts (P<.001). The use of debulking devices and stents was less in this group (P<.001). Procedural and in-hospital complications were similar. Follow-up at 6 months revealed nonsignificant but lower late loss (in-stent, 0.33+/-0.7 mm; in-lesion, 0.41+/-0.6 mm) in the 21-Gy group compared to the 18-Gy group; follow-up at 12 months revealed a trend toward less overall myocardial infarction, although repeat revascularization and MACE rates were similar.

Conclusions: IRT-gamma therapy for diffuse ISR lesions with a 21-Gy dose is clinically safe and feasible with marked reduction in late loss but does not confer additional benefit with regard to repeat revascularization and MACE when compared to a dose of 18 Gy.