A Prospective Longitudinal Cohort Study Looking at the Difference in Carotid Intima-medial Thickness Between Irradiated and Unirradiated Carotid Arteries in Patients With 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 large arteries in the neck, the carotid arteries, are often included in the area being treated with radiotherapy. There is some evidence to show that radiotherapy to these blood vessels can result in thickening and furring of the artery walls some years after treatment. This thickening may then result in stiffening and narrowing of the artery. 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 compare the thickness (intima-medial thickness) of the carotid artery wall over time (a period of 5 years) following radiotherapy to the thickness in carotid arteries that have not received radiotherapy. 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 are having only one side of the neck treated and use the other side as a comparison. The study will also be investigating 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, mean intimal-medial thickness at one year following radiotherapy will be the same as in unirradiated arteries. * The incidence of carotid ar