|On November 3, 2000, the Food and Drug Administration (FDA) granted
approval for two devices that deliver intracoronary radiotherapy for in-stent restenosis.
More than 500,000 percutaneous coronary revascularization procedures are performed each year in North America. Restenosis occurs in 30 to 40 percent of patients within six months after balloon angioplasty and in 20 to 30 percent of patients after balloon angioplasty followed by stenting. Consequently, there are more than 150,000 cases of restenosis each year, with an increasing number occurring in stented vessels. Intracoronary radiotherapy involves treating coronary stenoses with a radioactive source from within the artery. Two approaches include the implantation of a radioactive stent and the catheter-based delivery of radioactive seeds. With the first method, stents coated with radioactive isotopes are deployed at the site of the stenosis. With the second, a "ribbon" containing radioactive seeds is placed at the site of a coronary stenosis for a short period after percutaneous coronary revascularization.
Both beta-radiation and gamma-radiation sources have been studied. Beta radiation takes the form of electrons, or particulate energy, and has limited tissue penetration. Most of the therapeutic effect of beta radiation occurs 2 to 3 mm from the radioactive source. Gamma radiation takes the form of photons and penetrates well beyond 10 mm. Asummary of the trials showing the effectiveness of radiation in lowering the risk of restenosis is shown above.