Radiation and the Stent: Results From Catheter - Based Radiation. And Radioactive Stenting

Angiographic restenosis occurs in up to 60% of cases after balloon angioplasty (BA). Restenosis after BA occurs due to elastic recoil of the artery, vascular remodeling with vessel shrinkage and neointimal hyperplasia. Neointimal hyperplasia develops by migration and proliferation of smooth muscle cells (SMCs) and myofibroblasts after balloon-induced trauma of the arterial wall and by deposition of an extracellular matrix by the SMCs. By preventing elastic recoil and negative remodeling stent implantation has resolved many of the problems created by balloon angioplasty. However, a new problem has been created - that of in-stent restenosis, which is caused by neointimal hyperplasia. This entity occurs in 9-30% of cases after stent implantation. In the USA this equates to some 125,000 cases per year. Conventional treatment for in-stent restenosis (balloon angioplasty and debulking) has been unsuccessful with 50-80% of cases suffering from further restenosis. Alternative treatment modalities were clearly required. Since radiotherapy had proven to be effective in treating the exuberant fibroelasticity of keloid scar formation and other non-malignant process such as ocular pterygia, it was assumed that this adjunctive therapy may also inhibit coronary restenosis.