[Radiotherapy and atherosclerosis: current data and issues]

Association between modifiable vascular risk factors and rapid progression of postradiation carotid artery stenosis

BACKGROUND

Postradiotherapy carotid vasculopathy is a clinically relevant complication in patients with head and neck cancer receiving radiotherapy. In this study, we investigated the factors associated with the development and progression of carotid artery stenosis (CAS) in such patients.

METHODS

Patients who received radiotherapy for head and neck cancers between October 2011 and May 2019 at a medical center in Taiwan were eligible for inclusion in this study. This study included patients who underwent two consecutive carotid duplex examinations within an interval of 1 to 3 years. The factors associated with ≥50% CAS at baseline and follow-up were analyzed.

RESULTS

In total, 694 patients (mean age, 57.8 ± 9.9 years; men, 75.2%; nasopharyngeal cancer, 73.3%) were included. The mean interval between radiotherapy and carotid duplex examination was 9.9 ± 5.9 years. At baseline, 103 patients had ≥50% CAS, which was significantly associated with tobacco smoking, hypercholesterolemia, and a prolonged interval between radiotherapy and carotid duplex examination. A total of 586 patients did not have CAS at baseline; of them, 68 developed ≥50% CAS during follow-up. Hypertension and hypercholesterolemia were identified as independent risk factors for CAS progression.

CONCLUSION

Modifiable vascular risk factors, such as hypertension and hypercholesterolemia, appear to be significantly associated with the rapid progression of postradiotherapy CAS in patients with head and neck cancer.

Chronic Internal Exposure to Low Dose 137Cs Induces Positive Impact on the Stability of Atherosclerotic Plaques by Reducing Inflammation in ApoE-/- Mice

After Chernobyl and Fukushima Daï Chi, two major nuclear accidents, large amounts of radionuclides were released in the environment, mostly caesium 137 (137Cs). Populations living in contaminated territories are chronically exposed to radionuclides by ingestion of contaminated food. However, questions still remain regarding the effects of low dose ionizing radiation exposure on the development and progression of cardiovascular diseases. We therefore investigated the effects of a chronic internal exposure to 137Cs on atherosclerosis in predisposed ApoE-/- mice. Mice were exposed daily to 0, 4, 20 or 100 kBq/l 137Cs in drinking water, corresponding to range of concentrations found in contaminated territories, for 6 or 9 months. We evaluated plaque size and phenotype, inflammatory profile, and oxidative stress status in different experimental groups. Results did not show any differences in atherosclerosis progression between mice exposed to 137Cs and unexposed controls. However, 137Cs exposed mice developed more stable plaques with decreased macrophage content, associated with reduced aortic expression of pro-inflammatory factors (CRP, TNFα, MCP-1, IFNγ) and adhesion molecules (ICAM-1, VCAM-1 and E-selectin). Lesions of mice exposed to 137Cs were also characterized by enhanced collagen and smooth muscle cell content, concurrent with reduced matrix metalloproteinase MMP8 and MMP13 expression. These results suggest that low dose chronic exposure of 137Cs in ApoE-/- mice enhances atherosclerotic lesion stability by inhibiting pro-inflammatory cytokine and MMP production, resulting in collagen-rich plaques with greater smooth muscle cell and less macrophage content.