Effect of intracoronary gamma-radiation therapy on in-stent restenosis - An intravascular ultrasound analysis from the Gamma-1 study

Background-The aim of this study was to use serial volumetric intravascular ultrasound to evaluate the effect of gamma -radiation on recurrent in-sten t restenosis. Methods and Results-After successful reintervention, patients were randomiz ed to receive either Ir-192 Or placebo. Intravascular ultrasound studies wi th motorized pullback (0.5 mm/s) were performed immediately after irradiati on and at 8-month follow-up in 70 patients. Paired volumetric analysis of t he stented segment and of 5-mm proximal and distal reference segments was p erformed; this included measurements of the external elastic membrane, lume n, plaque and media (external elastic membrane minus lumen), stent, and int imal hyperplasia (stent minus lumen). Baseline proximal reference, stent, a nd distal reference measurements were similar in both groups. The changes i n proximal and distal reference measurements of the external elastic membra ne, plaque and media, and lumen areas were similar in both groups. However, the decrease in stented segment lumen volume was less in the Ir-192 patien ts than the placebo patients (-25+/-34 mm(3) versus -48+/-42 mm(3); P=0.022 5), and the increase in the volume of intimal hyperplasia in the stented se gment was less in the Ir-192 patients than in the placebo patients (28+/-37 mm(3) versus 50+/-40 mm(3); P=0.0352). When averaged over the length of th e stented segment (32+/-13 mm versus 33+/-14 mm; P=0.9), the increase in me an area of intimal hyperplasia was 0.8+/-1.0 mm(2) in the Ir-192 group and 1.6+/-1.2 mm(2) in the control group (P=0.0065). Late stent-vessel wall mal apposition was noted in one placebo patient and no Ir-192 patients. Conclusions-gamma -Radiation therapy can effectively prevent recurrent in-s tent restenosis by inhibiting neointimal formation within the stent. At the stent edge, there were no significant differences between Ir-192 and place bo patients.