Radioisotope stents.
Intracoronary stent placement following PTCA improves the long-term outcome of the treated patient, but in-stent restenosis remains problematic, especially in smaller vessels and longer lesions. Intravascular brachytherapy is a rapidly evolving field of research and clinical treatment, with a number of different irradiation techniques being used clinically. Many clinical data are now available that indicate clearly that either <FONT FACE="MetaPress 7">&#110</FONT> or <FONT FACE="MetaPress 7">&#103</FONT> radiation can reduce, and hopefully cure restenosis. The combination of radiation with stents has several distinct advantages over radiation with balloon angioplasty. It should be possible to use the stent as the radioactive source, as the radioactivity levels required by a permanent implant are extremely safe (< 1/1000 of the radioactivity of the least radioactive brachytherapy catheters). Once the stent has been implanted, the procedure is complete; catheter-based brachytherapy requires a second procedure after stent implantation. Unfortunately, in many human studies of the efficacy of radioisotope stents, although an excellent result in terms of a dramatically reduced neointima was seen in the stent, the incidence of an 'edge effect', with a reduced lumen just beyond the stent-edge occurred at an unacceptable rate. The encouraging results of the 'hot ends' study, where the stent ends were made more radioactive to reduce the edge effect, coincided with even more encouraging results from sirolimus drug-eluting stents. As a result, most work on radioisotope stents for the treatment of restenosis has been abandoned. There may, however, be applications for radioisotope stents in the treatment of malignant ducts, such as the esophagus and bronchia, which could justify further study of the devices.