title: Radiation-induced carotid artery atherosclerosis.
abstract: OBJECTIVE
  Carotid arteries frequently receive significant doses of radiation as collateral structures in the treatment of malignant diseases. Vascular injury following treatment may result in carotid artery stenosis (CAS) and increased risk of stroke and transient ischaemic attack (TIA). This systematic review examines the effect of radiotherapy (RT) on the carotid arteries, looking at the incidence of stroke in patients receiving neck radiotherapy. In addition, we consider possible surrogate endpoints such as CAS and carotid intima-medial thickness (CIMT) and summarise the evidence for radiation-induced carotid atherosclerosis.
  
  
  METHODS
  From 853 references, 34 articles met the criteria for inclusion in this systematic review. These papers described 9 studies investigating the incidence of stroke/TIA in irradiated patients, 11 looking at CAS, and 14 examining CIMT.
  
  
  RESULTS
  The majority of studies utilised suboptimally-matched controls for each endpoint. The relative risk of stroke in irradiated patients ranged from 1.12 in patients with breast cancer to 5.6 in patients treated for head and neck cancer. The prevalence of CAS was increased by 16-55%, with the more modest increase seen in a study using matched controls. CIMT was increased in irradiated carotid arteries by 18-40%. Only two matched-control studies demonstrated a significant increase in CIMT of 36% and 22% (p=0.003 and <0.001, respectively). Early prospective data demonstrated a significant increase in CIMT in irradiated arteries at 1 and 2 years after RT (p<0.001 and <0.01, respectively).
  
  
  CONCLUSIONS
  The incidence of stroke was significantly increased in patients receiving RT to the neck. There was a consistent difference in CAS and CIMT between irradiated and unirradiated carotid arteries. Future studies should optimise control groups.
authors.affiliation: Head and Neck Unit, Royal Marsden Hospital, London, United Kingdom.
authors.forename: Dorothy M
authors.initials: DM
authors.lastname: Gujral
authors.affiliation: Department of Echocardiography, Royal Brompton Hospital, London, United Kingdom.
authors.forename: Navtej
authors.initials: N
authors.lastname: Chahal
authors.affiliation: Department of Echocardiography, Royal Brompton Hospital, London, United Kingdom.
authors.forename: Roxy
authors.initials: R
authors.lastname: Senior
authors.affiliation: Head and Neck Unit, Royal Marsden Hospital, London, United Kingdom.
authors.forename: Kevin J
authors.initials: KJ
authors.lastname: Harrington
authors.affiliation: Head and Neck Unit, Royal Marsden Hospital, London, United Kingdom. Electronic address: Christopher.Nutting@rmh.nhs.uk.
authors.forename: Christopher M
authors.initials: CM
authors.lastname: Nutting
mesh_terms: D002339:Carotid Arteries / Q000528:radiation effects; D002340:Carotid Artery Diseases / Q000209:etiology*; D006258:Head and Neck Neoplasms / Q000532:radiotherapy; D006801:Humans; D011446:Prospective Studies; D011832:Radiation Injuries / Q000209:etiology*; D020521:Stroke / Q000209:etiology
keywords: Atherosclerosis; Carotid artery; Radiotherapy