Orlando, FL - Gamma radiation has proved as effective in preventing recurrence of in-stent restenosis in saphenous vein grafts (SVGs) as it was previously shown for native coronaries. This was the verdict pronounced by Dr Ron Waksman (Washington Hospital Center, Washington, DC) as he presented the results of the SVG WRIST trial at the American College of Cardiology 50th Annual Scientific Session Late Breaking Clinical Trials.

SVG WRIST is the first multicenter randomized clinical trial to examine the efficacy and safety of gamma radiation for the treatment of in-stent restenosis in SVGs. Previous trials have confirmed efficacy and safety of gamma radiation for in-stent restenosis in native coronaries, leading to FDA approval of the Cordis Checkmate? gamma radiation system for that indication. In-stent restenosis in bypass grafts is a particularly severe and frequent problem, and therefore an attractive target for radiation therapy.

In SVG WRIST, 120 patients with angina and evidence of in-stent restenosis in SVGs were randomized to Ir-192 or placebo treatment, following successful PTCA with provisional stenting, laser, or atherectomy. The cohort was slightly older than in previous gamma radiation studies (65-67 years on average), and almost all patients had hyperlipidemia and hypertension. In addition, both placebo and radiation cohorts showed reduced LVEF (46%-48%).


Restenosis rates at 6 months following gamma radiation for in-stent restenosis of SVG

Vessel segment Placebo (%) Ir-192 (%) % change with radiation p value Stent 43 15 65% 0.004 Injured 45 17 62% 0.004 Radiated 45 17 62% 0.005 Analysis 45 21 53% 0.005

MACE at 6 months following gamma radiation for in-stent restenosis of SVG

Vessel segment Placebo (%) Ir-192 (%) % change with radiation p value Death 5.0 3.3 NA 1.0 Q-wave MI 3.3 1.7 NA 1.0 PTCA 53.3 15 72% decrease <0.001 TLR 48.3 10 79% decrease <0.001 TVR 53.3 18.3 65% decrease <0.001 Any MACE 55 20 64% decrease <0.001 Late thrombosis 1.7 1.7 NA NA

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At 6 months, the radiation cohort showed a dramatic reduction in angiographic and clinical recurrence, as compared to placebo (50-79% reduction). Restenosis rates and late loss were significantly lower in all vessel segments analyzed in the radiation group. There was also little evidence of edge effect. This translated into significantly fewer revascularization procedures in the radiation group, while death, MI, and late thrombosis remained similar between the cohorts. Preliminary angiographic results from 12 months suggest the good news holds true.

Waksman concluded, "Gamma radiation for the treatment of in-stent restenosis in SVG demonstrated similar results to those reported previously in native coronary arteries." Furthermore he proposed, "the SVG WRIST data should support extension of the indications for the use of catheter-based gamma radiation for the treatment of in-stent restenosis in SVGs."

Kat Rother kat@conceptis.com

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