Effect of Intracoronary (gamma)-Radiation Therapy on In-Stent Restenosis: An Intravascular Ultrasound Analysis from the Gamma-1 Study

Reviewers: Li Liu, MD
Source: Circulation, volume 102: 2915-2918, (December) 2000

Précis: Intracoronary gamma-radiation therapy prevents in-stent restenosis

Introduction

Despite its wide acceptance, coronary angioplasty is limited by rates of restenosis of 30 to 60 percent (Circulation 1991 Sep; 84(3): 1426-36). In recent years, much has been learned about the mechanism of restenosis, which can be divided into two broad components. The first component, recoil and remodeling, involves the mechanical collapse and constriction of the treated vessel. The second component, intimal hyperplasia is the proliferative response to injury, which consists largely of smooth muscle cells and matrix formation (J Am Coll Cardiol 1993 Jan; 21(1): 15-25). Several clinical trials using local, catheter-based ionizing radiation have demonstrated significantly reduced neointimal proliferation in in-stent restenosis (Circulation 2000 May 9; 101(18): 2165-71). In this study, the researchers assessed the effectiveness of gamma-radiation in patients with recurrent in-stent restenosis.

Method

A total of 70 patients who required reintervention for in-stent restenosis were treated with either balloon angioplasty, atheroblation and/or additional stent placement and were then randomized to receive either intracoronary gamma-radiation from iridium-192 source or placebo.

Results

• All the reference measurements were similar in both groups
• Patients who received intracoronary gamma-radiation had less decrease in lumen volume, and a smaller increase of hyperplasia in the stented segment compared with the placebo-treated group.

Discussion

In this study, by inhibiting neointimal formation, intracoronary gamma-radiation therapy effectively prevented recurrent in-stent restenosis. Gamma radiation with iridium-192 appeared to be a promising new treatment for patients with restenosis. Larger studies with longer-term follow-up are needed to make definitive conclusion.