Vascular events from carotid artery atherosclerosis after radiation therapy for laryngeal and hypopharyngeal cancer: the incidence and risk factors

In this retrospective cohort study, we evaluated the incidence of vascular events from carotid artery atherosclerosis after radiotherapy indication for laryngeal and hypopharyngeal cancer. From January 2007 to December 2016, we investigated 111 laryngeal/hypopharyngeal cancer patients who underwent curative radiotherapy and were followed up for ≥1 year (median follow-up duration, 60 months). We evaluated the incidence of vascular events from carotid artery atherosclerosis, defined as a transient ischemic attack or an atherothrombotic cerebral infarction, or from undergoing treatment such as carotid artery stenting for carotid artery stenosis. The median radiation dose was 66 Gy (range, 60–74); 48 patients (43.2%) received concurrent chemotherapy. The 5-year overall survival was 86.2%. Six patients required treatment for carotid artery disease. Carotid stenting was performed in three patients with carotid artery stenosis; three patients developed atherosclerotic cerebral infarction and received medical treatment, with a median of 51.7 months (range, 0.3–78.3) after radiotherapy initiation. The vascular event occurrence rate was 5.4% within 5 years and 10.7% within 8 years. In the univariate analysis, dyslipidemia, diabetes mellitus, and carotid calcification were significant factors for event occurrence. Because three out of six cases occurred out of the irradiated field, no carotid artery or carotid bulb dosimetric parameters showed significant correlation. As laryngeal/hypopharyngeal cancer patients, particularly with complications including dyslipidemia and diabetes mellitus, are at a high risk of carotid artery stenosis after radiotherapy, long-term carotid artery evaluation is necessary. Early intervention by stroke specialists can reduce the risk of fatal cerebral infarction.