Radiation effects on the intima–media thickness of the common carotid artery in post-radiotherapy patients with head and neck malignancy M Shariat, 1 N A A Alias, 2 B M Biswal 2 1 Radiology Department, Hospital Universiti Kebangsaan Malaysia, Cheras, Kuala Lumpur, Malaysia; 2 Radiology Department, Hospital Universiti Sains Malaysia, Kubang Kerian, Kelantan, Malaysia Correspondence to: Dr M Shariat, Radiology Department, Hospital Universiti Kebangsaan Malaysia, Cheras, Kuala Lumpur, Malaysia; masoudshariat@gmail.com Received 4 February 2008 Accepted 21 July 2008 ABSTRACT Background: Post-radiation large vessel injury has not received as much attention as microvascular irradiation injury. A few studies have shown that common carotid intima–media thickness (IMT) is increased after radio- therapy to the head and neck. However, in most of these studies, the irradiated subjects also had other major risk factors for atherosclerosis. In this study, irradiated subjects with major risk factors such as hypertension, diabetes, history of previous cerebrovascular accident and connective tissue disorder were excluded. Objective: To show in a cross-sectional study if radiotherapy to the carotid area has any effect on the IMT of the common carotid artery. Subjects and methods: 13 patients with head and neck malignancies who had completed radiotherapy to the carotid region at least 1 year previously underwent ultrasound of the carotid artery. IMT measurements were compared with those of 13 healthy controls, matched for age, sex and race, with no history of radiotherapy. Results: The irradiated subjects had significantly larger IMT measurements (mean 0.74 mm) than the non- irradiated subjects (mean 0.46 mm). The difference was significant (p,0.001) with a confidence interval of 95%. Conclusions: This study shows that there is a measurable, significant (p,0.001) increase in IMT of the common carotid artery after radiotherapy for head and neck malignancy compared with non-irradiated matched controls. This knowledge is important for risk–benefit assessment of prophylactic or therapeutic neck irradia- tion. Increased awareness of this complication should provide an opportunity to intervene and prevent future cerebrovascular accidents in the majority of such patients. Radiotherapy as a single modality or in combination with surgery has been widely used in the treatment of head and neck tumours for many years, and this has resulted in marked improvement in survival of patients with these tumours, who previously had a dismal prognosis. Successful treatment increases survival but also puts the patient at risk of radiation-related side effects. Of these, vascular side effects are serious and may be life-threatening. It has traditionally been accepted that the carotid is fairly resistant to the fibrosis and narrowing that are evident in smaller vessels undergoing comparable radiation exposure. 1 Nevertheless, thrombosis, carotid rupture, and progressive stenosis have all been described. 2 The exact mechanism of radiation injury remains uncertain. One histological case report described evolution of injury to the vasa vasorum and periadventitial tissues (early lesion), which may progress to a late lesion with dense pre-adventitial fibrosis. Injury to the vasa vasorum and conse- quent ischaemic lesions of the arterial wall were thought to be morphological features distinguish- ing radiation-induced arterial injury from sponta- neous atherosclerosis. 3 The changes are thought to occur in an accelerated manner; however, the time course of the appearance of clinical symptoms remains to be defined. The traditional dogma that radiation- related changes take 10–15 years to reach clinical significance has been questioned. 4 Induction of a thrombosis of the carotid has been postulated 4 to explain the early (within 36 months) appearance of symptoms in young patients (age 25–40 years), although work in the laboratory has documented ‘‘physiological aging’’ and plaque formation in the carotid within days of radiation exposure. 5 The main sequelae of carotid atherosclerosis include transient ischaemic attacks, ischaemic strokes, acute thrombosis, carotid rupture, carotid wall thickening and amaurosis fugax. The reported intervals between irradiation and first symptoms range from 6 months to more than 20 years. 6 Many factors have been associated with increased risk of developing atherosclerosis—for example, increasing age, diabetes mellitus, hyper- tension, hypercholesterolaemia, smoking 7 and irra- diation to the affected vessels. 8 Measurement of the intima–media thickness (IMT) of the common carotid artery is feasible with today’s high-resolution ultrasound machines. When the ultrasound beam is at right angles to the carotid walls, two white lines are seen in the vessel, particularly on the far wall. The first line corre- sponds to the blood–intima boundary and the second to the outer media–adventitia region. The IMT is the distance between these two interfaces. 9 Change in IMT of the carotid arteries has become well established in epidemiological studies as a marker of the early changes of atherosclerosis. 7 It has also proven to be a powerful predictor of future cerebrovascular disease. 10 This study was conducted to determine if irradiation to the carotid area for treatment of head and neck malignancy has any latent effect on IMT of the common carotid artery in comparison with non-irradiated subjects matched for age, sex and race. SUBJECTS AND METHODS Study design This study was a cross-sectional study conducted in the Radiology Department of the Hospital Original article Postgrad Med J 2008;84:609–612. doi:10.1136/pgmj.2008.068569 609 Downloaded from https://academic.oup.com/pmj/article/84/997/609/7026389 by guest on 09 February 2023