A Cross-sectional Study Looking at the Effect of Radiotherapy on Carotid Intima-medial Thickness in Head and Neck Cancer

Some patients with head and neck cancer or benign tumours of the head and neck receive radiotherapy to their neck as part of their treatment. The carotid arteries are often included in the radiotherapy as collateral structures. There is some evidence to show that radiotherapy to these blood vessels can result in thickening of the artery walls some years after treatment and increased risk of stroke or TIA in the future.

Current research is now aimed towards detecting radiotherapy-related changes to the carotid arteries at an earlier stage and towards using new radiotherapy techniques to avoid treating these blood vessels if possible. The question of whether or not the use of preventive medicines like aspirin and cholesterol-lowering tablets helps to reverse this process is currently unanswered.

The aim of this study is to measure the thickness (intima-medial thickness) of irradiated carotid artery walls and compare this to unirradiated arteries. There are many other causes for thickening of arteries (such as high blood pressure, high cholesterol levels and diabetes) and these may affect the ability to measure the effect of radiotherapy change to the artery wall. In order to address this, it is ideal to look at this process in patients who have only had one side of their neck treated and use the other side as a comparison. The study will also be looking for earlier signs of radiotherapy-related changes, such as stiffening of the artery wall, inflammation in the artery wall (a very early sign of radiotherapy-related change) and some markers in the blood that may indicate that this process is taking place.

The null hypotheses of this study are:

• In irradiated carotid arteries, the mean intimal-medial thickness will be the same compared to unirradiated arteries.
• Serum biomarkers will not be elevated in radiation-induced carotid atherosclerosis.
• Development of radiation-induced carotid atherosclerosis is not affected by risk factor modulation (Aspirin, HMGCoA reductase inhibitors, smoking cessation).
• There is no difference in carotid arterial wall strain in irradiated carotid arteries versus unirradiated carotid arteries.
• Microbubble ultrasound will not be able to detect Inflammation in the carotid arteries as an early marker of atherosclerosis.