Brachytherapy with iridium-192 HDR to prevent from restenosis in peripheral arteries. An update.

The use of stents does not appreciably improve restenosis (usually resulting from intimal hyperplasia) as compared to percutaneous transluminal angioplasty (PTA) alone. The development of small-caliber probes for afterloading therapy in the biliary tract allowed us to use these for therapy in the vascular system. Using a special 9 F catheter, exact measurement of the length of the stented vascular segment and of the insertion length of the afterloading probe could be reproducibly performed. We used a Nucletron (Micro) Selectron HDR planning system version 10.10 for exact calculation, monitoring, and control of the afterloading procedure. Our source was iridium 192 (10 Ci) with a diameter of 1.1 mm. The program controls and monitors the insertion and removal of the iridium probe from the source into the special catheter through to the tip, and monitors the irradiation duration. The exposure time was around 200 seconds for a surface dose of 12 Gy. To date, a total of 40 patients have been treated with endovascular afterloading. All patients suffered from clinically relevant reocclusions or restenoses in stented vascular segments of the superficial femoral artery following successful PTA or laser treatment, within 6 to 8 months after the last therapy. In all patients it was possible to perform re-PTA treatment without remaining residual stenoses in the stented region. The additional time required as compared to PTA alone was approximately 45 minutes with most of this time spending for transportation between the cath lab and afterloading room. The follow-up period of the 40 patients ranged from 4 months to 71/2 years. In 33 patients, there was no deterioration of the clinical stage and no restenosis. One patient suffered from an acute thrombosis approximately 3 months after stent implantation, another patient had a stenosis 3 cm above the stented vascular segment 12 months after irradiation treatment. Follow-up examinations have revealed no evidence of nerve lesions following irradiation therapy. The tissue surrounding the artery showed no change following irradiation therapy, either in the CT, color-coded Doppler, endovascular ultrasonic scan or MRI. No complaints of discomfort were reported during or after irradiation. With the exceptions mentioned above, there was no evidence of any complications.

Five year follow-up after brachytherapy for restenosis in peripheral arteries.

Restenosis in peripheral vessels caused by intimal hyperplasia after stent implantation, PTA, atherectomy or laser treatment ranged up to 40%. In order to avoid the hyperplastic reaction with restenosis we treated our patients with prophylactic endovascular afterloading therapy after failure of PTA in case of recurrent stenosis. We had 30 patients with up to 4 recurrent stenoses between 4 and 7 months due to intimal hyperplasia in the stented area. To minimize the reocclusion rate we performed an irradiation with 12 Gy surface dose in one session using the endovascular afterloading method with 192 Iridium HDR following re-PTA in the stented vessel segment. The longest follow up is 68 months. The histological analyses of tissue years after irradiation showed a thinner, more compact cellular layer of the myofibroblasts with less myxoid degeneration between the cells compared to intimal hyperplasia and plaques in not irradiated vessel segments. The follow up showed a significant effect of endovascular radiotherapy. The histological findings after irradiation were a diminished growth in the cellular population of the analysed vessel wall compared to not irradiated vessel wall segments of the same patient. These findings may be explained by a reduced migration and mitosis rate of myofibroblastic cells after irradiation. The method may be an interesting alternative to stent implantation alone. Even vessel segments like the Hunter's channel will be patent for a long time follow up. Because of the steep decay in the dose using the endovascular irradiation method with 192 iridium HDR, the method can be used with minimal risk for the surrounding tissue.