Effect of catheter-based iridium-192 gamma brachytherapy on the added risk of restenosis from diabetes mellitus after intervention for in-stent restenosis (subanalysis of the GAMMA I Randomized Trial)

Catheter-based intracoronary radiation therapy using iridium-192 (Ir-192) has been shown to be effective in reducing recurrent coronary restenosis after initial percutaneous treatment of in-stent restenosis. Patients with diabetes mellitus (DM) have a higher risk of recurrent restenosis than nondiabetics for nonstented and in-stent restenosis coronary lesions. The use of Ir-192 for preventing recurrent restenosis in such patients remains undefined. The GAMMA I trial was a prospective, randomized, double-blind, multicenter trial of 252 patients with in-stent restenosis who underwent percutaneous coronary intervention and were assigned to receive either Ir-192 (131 patients) or catheter-based placebo (121 patients). DM was present in 79 patients (31%) (41 patients received Ir-192 and 38 patients received placebo) and was absent in 173 patients (90 patients received Ir-192 and 83 patients received placebo). At 6-month follow-up in the GAMMA I trial, the angiographic in-lesion binary restenosis rate was lower in the Ir-192 arm than in the placebo arm (32.4 vs 55.3, p = 0.01). When patients were stratified by the presence of DM, the antirestenosis effect of Ir-192 was larger for diabetic patients than for nondiabetic patients (absolute in-lesion restenosis rate was reduced by 40% for diabetics and 16% for nondiabetics). Thus, adjunctive Ir-192 intracoronary radiation therapy reduces recurrent restenosis after intervention for in-stent restenosis in patients with and without DM. The relative impact of this treatment is more pronounced in diabetic patients because it appears to neutralize the added risk of recurrent restenosis seen in proliferative diabetic lesions.