Introduction: Modern radiotherapy of head and neck cancers involves high dosage of radiation per tissue volume including carotid arteries. Little is known about the mechanism of influence of radiotherapy to the large carotid arteries it may lead to inflammatory condition in the vascular wall, intima-media thickness (IMT) of the vessel and increase atherosclerosis. This work is based on current knowledge and presents the results of research which is based on ultrasound assessment of IMT and atheromatous changes in the carotid artery in a group of 61 irradiated patients with head and neck tumors.
Objectives: To assess IMT, the progression of the atheromatous changes in the carotid arteries of patients who had completed radiotherapy in comparison with a control group of non-treated patients and to determine the relation between the progression of the atheromatous changes, the radiation dosage and time after their radiotherapy.
Patients and method: The ultrasound tested carotid arteries of 61 patients. The mean of the dose in the carotid area was 50.7 ± 10.6 Gy, and the time after the therapy completion was 41 ± 27 months. The results were compared with the measurement in the control group--62 people of similar age and risk of atherosclerosis. The stenosis was assessed using planimetric and hemodynamic methods and the structure of the plaque was assessed according to Gray-Weale.
Results: The average size of IMT on the front wall of the common carotid artery (CCA) is significantly bigger than on the opposite wall, p = 0.0149. There was shown no statistic difference concerning the average size of IMT (assessed on the posterior wall of the arteries) between the group of patients after radiotherapy and the control group (p = 0.1877). It has been proven that the frequency of occurrence of plaque in the carotid arteries in the patients who had completed radiotherapy compared to the control group is 16.3% bigger. The dominant type of plaque in the group of patients who had completed radiotherapy are heterogeneous plaques with majority of low echoes Type 2 or high echoes Type 3. The surface of the plaque in the group of patients is mostly irregular in comparison with the control group. There is no relationship between the thickness of IMT and the size of dosage. However, when considering the age of the patients there is an increase of IMT depending on the radiation dosage. It has been proven that the increase of IMT for patients below 63 years of age is bigger than for patients over 63. In the last statistical analysis, which studied the influence of time after the termination of treatment on the IMT, it has been proven that there is a small correlation of there parameters but not significant from the statistical point of view.
Conclusion: The results of the research show that radiotherapy influences large carotid arteries by accelerating the IMT in the younger age group below 63 years of age. Radiation increases the frequency of plaque in carotid ateries and the creation of plaque of heterogeneous structure. Understanding the increase of IMT and the presence of hemodynamically important atherosclerosis as a significant risk factor for cerebro-vascular accident we need to consider the introduction of ultrasound scan as a routine test in the assessment of carotid arteries in patients who had completed radiotherapy to the head and neck area.