B E Powers1, H D Thames, E L Gillette. 1. Department of Pathology, Colorado State University, Fort Collins, USA. bpowers@vth.colostate.edu
Abstract
PURPOSE: To determine the long-term effects of irradiation on large arteries in view of the possible use of radiation to prevent restenosis after angioplasty. METHODS AND MATERIALS: Groups of dogs received 10-55 Gy single-dose alone, or in combination with 50 Gy in 2-Gy fractions, or 50-80 Gy in 2-2.7-Gy fractions to an 8-cm length of aorta and branch arteries. Single doses were delivered intraoperatively. Two or 5 years after irradiation, aortas and branch arteries were evaluated histomorphometrically to determine areas of intima, media, and adventitia, and qualitatively to determine other adverse effects. RESULTS: Intimal area increased at single doses < 20 Gy and after all fractionated doses, but was normal at doses > 20 Gy 2 years after irradiation. Intimal area was greater at 5 years than at 2 years after irradiation. Adventitial area increased with increasing dose at 2 and 5 years after irradiation. Thrombosis of the aorta and branch arteries occurred at 4-5 years after irradiation with ED50s of 29.7 Gy and about 25 Gy, respectively, but did not occur after fractionated irradiation. CONCLUSION: Intimal proliferation is inhibited at single doses > 20 Gy, but may be stimulated at single doses of < 20 Gy or after fractionated irradiation. Adventitial fibrosis increases with increasing dose and could contribute to adverse late vascular remodeling. Severe adverse effects were not evident until 4-5 years after irradiation at does of > 20 Gy to an 8-cm vessel length.
PURPOSE: To determine the long-term effects of irradiation on large arteries in view of the possible use of radiation to prevent restenosis after angioplasty. METHODS AND MATERIALS: Groups of dogs received 10-55 Gy single-dose alone, or in combination with 50 Gy in 2-Gy fractions, or 50-80 Gy in 2-2.7-Gy fractions to an 8-cm length of aorta and branch arteries. Single doses were delivered intraoperatively. Two or 5 years after irradiation, aortas and branch arteries were evaluated histomorphometrically to determine areas of intima, media, and adventitia, and qualitatively to determine other adverse effects. RESULTS: Intimal area increased at single doses < 20 Gy and after all fractionated doses, but was normal at doses > 20 Gy 2 years after irradiation. Intimal area was greater at 5 years than at 2 years after irradiation. Adventitial area increased with increasing dose at 2 and 5 years after irradiation. Thrombosis of the aorta and branch arteries occurred at 4-5 years after irradiation with ED50s of 29.7 Gy and about 25 Gy, respectively, but did not occur after fractionated irradiation. CONCLUSION: Intimal proliferation is inhibited at single doses > 20 Gy, but may be stimulated at single doses of < 20 Gy or after fractionated irradiation. Adventitial fibrosis increases with increasing dose and could contribute to adverse late vascular remodeling. Severe adverse effects were not evident until 4-5 years after irradiation at does of > 20 Gy to an 8-cm vessel length.