A Prospective Study of the Effects of Irradiation on the Carotid Artery

OBJECTIVES/HYPOTHESIS: To prospectively assess the effects of irradiation on the carotid artery in patients with head and neck cancer, as a possibly relevant factor in cancer treatment planning. STUDY DESIGN: Prospective study from a tertiary care academic setting on university (22 patients) and Veterans Affairs (14 patients) hospital patients; 1-year follow-up, including comparison of study data with age-matched and sex-matched control subjects from epidemiological studies. METHODS: Thirty-six patients with head and neck cancer who underwent therapeutic neck irradiation were examined by high-resolution ultrasound before and 1 year after treatment. Twelve patients were also studied at 2 years. Measurements included the intima-media thickness (IMT) of the carotid artery wall, the degree of stenosis as estimated from velocity measurements, and the presence and size of plaque. RESULTS: The pretreatment carotid IMT at baseline was 0.68 mm and was comparable to age-matched and sex-matched control subjects. Significant increase in the IMT was observed on both the left (0.67 vs. 0.84 mm) and the right (0.7 vs. 0.87 mm) sides (P < .001) 1 year after irradiation. In 12 patients who completed 24 months of follow-up the carotid IMT continued to significantly increase statistically compared with that at the first year after treatment (left side, 0.79 vs. 0.85 mm, P = .037; right side, 0.79 vs. 0.95 mm, P = .014). Statistically significant thickening of the carotid wall developed in all 36 patients by 1 year. Two patients experienced post-treatment neurological events and an area of stenosis greater than 75%. CONCLUSIONS: Neck irradiation significantly increases the thickness of the carotid wall during the first year after treatment--on average, 21 times more than in epidemiologically matched control volunteers. This phenomenon should be taken into consideration when planning treatment for the node-negative (NO) neck.