Abstract TP415: A Pilot Study on the Effect of Neck Irradiation Treatment for Nasopharyngeal Carcinoma on Carotid Artery Stenosis

Abstract

Introduction: Extracranial carotid stenosis, a risk factor for ischemic stroke, is thought to be accelerated by irradiation to the neck region. Nasopharyngeal carcinoma (NPC) has a predilection for East Asian with an incidence of 200-300 annually in Singapore. We studied the prevalence and severity of extracranial carotid disease in patients with prior neck irradiation for NPC, who were at different timepoints from the time of irradiation. Hypothesis: The prevalence of extracranial carotid disease is high among patients with prior neck irradiation, and this may justify a screening programme for early detection and primary stroke prevention. Methods: We conducted a pilot study to examine 50 patients (median age 55.2 years) with prior radiation for NPC with intensity-modulated radiation therapy (IMRT): 26 with <5 years after treatment and 24 with >=5 years after treatment. All patients received radiation therapy to the neck. Carotid disease was assessed by duplex sonography for severity of stenosis. The European Carotid Surgery Trial (ECST) criteria was employed for assessment for degree of stenosis. Results: Among patients with IMRT >=5 years ago, 25% (6/24) had carotid stenosis of >=50% compared to only 8% (2/26) of patients with IMRT within 5 years. Of these 8 patients with carotid stenosis >=50%, 5 (63%) had plaques with irregular or ulcerated surfaces, which is known to be associated with stroke risk. Based on these preliminary data, the study would require a larger sample size of 100 in each group to be powered at 90% with an alpha of 0.05. All 8 patients with carotid stenosis >=50% from the screening were referred for further evaluation for symptoms and risk factors, and management for secondary stroke prevention. Conclusions: Based on our findings, there is a rationale for screening for carotid disease among patients with prior neck irradiation and the timing of screening is more optimal after 5 years from IMRT. Patients found to have carotid disease should be counselled about risk factor control, antiplatelet medication and possibly carotid intervention for primary stroke prevention.