Brachytherapy (endocoronary curietherapy) for the treatment of restenosis

Restenosis after coronary angioplasty: Restenosis after coronary angioplast y remains a common clinical problem. Even after the advent of stenting, the rare of restenosis is still to the order of 20% or even higher in certain patient subgroups. Treatment is difficult, particularly in case of diffuse restenosis within stent lumens. Potential contribution of brachytherapy: After stent implantation, restenos is is generally due to excessive intimal proliferation producing a "benign tumor" formation that progressively obstructs the arterial lumen. Endocoron ary curietherapy has been proposed for its "antiproliferative'' effect. Systems used: Two radiation sources are used: gamma emitters with powerful tissue penetration properties, and beta emitters which exhibit less tissue penetration. Radioprotection is a greater problem with gamma emitters but d osimetry is more difficult to control with beta emitters. In clinical pract ice, the sources are placed close to the target site via conventional percu taneous catheterization and are employed as a complement to standard angiop lasty used to destroy the stenosis. Endocoronary brachytherapy requires clo se collaboration between the interventional cardiologist and the radiothera pist. Clinical trials: After the preliminary feasibility studies, several randomi zed trials have assessed the contribution of brachytherapy in the preventio n of restenosis. Using gamma emitters (Ir-192), the SCRIPPS, WRIST and GAMM A-1 studies demonstrated good immediate safety and a real effect on resteno sis with 50% reduction. inversely groups of treated patients have a higher rate of severe complications (death and infarction) related to late acute c oronary thrombosis after interruption of antiplatelet therapy combining tic lopidin and aspirin. These complications result from the frequent introduct ion of stents during angioplasty procedures and by delayed endothelializati on of the scents leaving a starting point for thrombosis formation longer t han usual. The same type of complications have been observed with beta brac hytherapy in the PREVENT trial, while in the START trial that used the Sr-9 0/y source in 476 patients, severe events were not more frequent in the irr adiated group. in the latest trial, the frequency of new stent implantation s was lower (21%) and antiplatelet treatment was maintained longer. Finally , the rate of restenosis was significantly lower (29% versus 45%). Practical applications: Current data confirm the efficacy of endocoronary b rachytherapy to limit intimal proliferation after angioplasty and reduce th e rate of restenosis. The question of safety remains open, with the potenti al risk of late coronary thrombosis; no long-term data (more than 5 years) are available. It is undoubtedly too early to propose routine use of brachy therapy, excepting perhaps cases where interventional cardiology raises par ticularly difficult problems, for example in case of diffuse restenosis wit hin an endoprosthesis.