Samarium-153 for intravascular irradiation therapy with liquid-filled balloons to prevent restenosis: acute and long-term results in a hypercholesterolemic rabbit restenosis model

Background: It has been shown that irradiation with either beta and gamma sources inhibit neointimal formation. Samarium-153 (¹⁵³Sm) is an isotope with 0.8 MeV, subdivided in three different beta energies and 103 keV of gamma energy. This compound has been tested and used in humans for palliation of pain from bone metastases. The aim of the present study was to evaluate the feasibility and efficacy of brachytherapy with ¹⁵³Sm-filled balloon to inhibit neointimal formation in rabbits after balloon overstretch injury.Methods: Nineteen rabbits underwent balloon injury in their iliac arteries. In 12 animals (control), oversized balloons filled with saline solution were inflated up to 5 atm for a period of 5 min. In 7 rabbits, the same procedure was performed but using balloons filled with ¹⁵³Sm. In all cases, both iliac arteries were treated. The prescribed radiation dose was 15 Gy at 1 mm depth. After 30 days, the animals were sacrificed and their arterial segments were analyzed. Radiation exposure at the animal chest to the table and at a distance of 1 m from the table was measured.Results: Histopathologic analysis showed a striking reduction in the amount of neointima in the irradiated arteries compared with control vessels (0.36±0.21 vs. 1.07±0.56 mm², P<.01). The dose delivered to the animal chest was 21.5 mR/h, whereas only 1.9 mR/h was measured at the table and virtually no radiation could be detected at a distance of 1 m from the table.Conclusions: Brachytherapy with ¹⁵³Sm was feasible with minimal personnel exposure radiation and effectively inhibited neointimal formation in this experimental model. These results warrant further experimental and clinical investigations.