Do traditional risk stratification models for cerebrovascular events apply in irradiated head and neck cancer patients?

BACKGROUND: Primary radical radiotherapy (RT) for head and neck cancer (HNC) often results in significant radiation dose to the carotid arteries. AIM: We assessed whether HNC patients are at increased risk of a cerebrovascular event primarily due to RT or other risk factors for atherosclerosis by (i) risk-stratifying patients according to validated QRISK-2 and QSTROKE scores and (ii) comparing the prevalence of carotid artery stenosis (CAS) in irradiated and unirradiated carotid arteries. DESIGN: HNC patients treated with an RT dose >50 Gy to one side of the neck ≥2 years previously were included. METHODS: QRISK-2 (2014) and Q-STROKE (2014) scores were calculated. We compared the prevalence of CAS in segments of the common carotid artery on the irradiated and unirradiated sides of the neck. RESULTS: Fifty patients (median age of 58 years (interquartile range (IQR) 50-62)) were included. The median QRISK-2 score was 10% (IQR 4.4-15%) and the median QSTROKE score was 3.4% (IQR 1.4-5.3%). For both scores, no patient was classified as high risk. Thirty-eight patients (76%) had CAS in one or both arteries. There was a significant difference in the number of irradiated arteries with stenosis (N = 37) compared with unirradiated arteries (N = 16) (P < 0.0001). There were more plaques on the irradiated artery compared with the unirradiated side - 64/87 (73.6%) versus 23/87 (26.4%), respectively (P < 0.001). CONCLUSIONS: Traditional vascular risk factors do not play a role in radiation-induced carotid atherosclerosis. Clinicians should be aware that traditional risk prediction models may under-estimate stroke risk in these patients.