Vascular radiolesion as a deleterious effect of high-dose-rate intraarterial brachytherapy with samarium-153 in hypercholesterolemic rabbits.

OBJECTIVE This study was designed to evaluate vascular morphological and morphometric changes induced by brachytherapy with samarium-153 (Sm-153) at high doses in hypercholesterolemic rabbits. METHODS Forty-three New Zealand White hypercholesterolemic rabbits were analyzed, and the total of 86 iliac arteries underwent balloon angioplasty injury. The rabbits were divided into three different groups: two irradiation groups (IG) assigned to 15 Gy (n=14) and 60 Gy (n=36) irradiation doses, respectively, and a control group (n = 36). Histomorphometric and qualitative histological analyses were performed for tissue evaluation. RESULTS Significant reductions were found in neointimal proliferation (NIP) (p< 0.0001), media area (MA) (p<0.0001) and percent stenosis (p<0.0001) in the 15-Gy IG, compared to the other groups. The 60-Gy IG had the higher rate of NIP, increase in media and vessel areas (VA) and percent stenosis. The 60-Gy IG also showed the greatest number of xanthomatous cells (60-Gy IG: 86.11% and 15-Gy IG: 14.29%, p<0.0001) and the highest amount of hyaline amorphous tissue (60-Gy IG:58.33% and 15-Gy IG:0%, p=0.0001) and vascular proliferation (60-Gy IG:30.56% and 15-Gy IG:0%, p=0.0221). No statistically significant differences were found among groups concerning other tissue analyses. CONCLUSION The high-dose irradiation of 60 Gy resulted in intense cell proliferation considered vascular radiolesion, unlike the 15-Gy dose, which was associated with an excellent inhibition of neointimal proliferation.