title: Carotid dosimetry for T1 glottic cancer radiotherapy.
abstract: OBJECTIVE
  Radiotherapy for T1 glottic cancer is commonly delivered using a lateral parallel opposed pair of megavoltage photon fields. There is increasing reported evidence of cerebrovascular events due to radiation-induced carotid stenosis. An alternative field arrangement is to use an anterior oblique technique. This study compares the carotid dosimetry between the two techniques and reviews the evidence for the risk of radiation-induced vascular events.
  
  
  METHODS
  The radiotherapy plans of 10 patients with T1 glottic cancer treated with an anterior oblique technique were examined for carotid dose. Alternative plans were then created using a parallel opposed pair of fields and the dose to the carotids compared. All patients received 50 Gy in 16 fractions treating once daily, for 5 days in a week.
  
  
  RESULTS
  The average of the mean dose to the carotids with the anterior oblique technique was 21 Gy compared with 37 Gy using the lateral parallel opposed pair arrangement (p < 0.0001).
  
  
  CONCLUSIONS
  An anterior oblique field arrangement for the treatment of T1 glottic cancer results in a significantly lower radiation dose to the carotid arteries, which may be clinically important in terms of reducing the risk of cerebrovascular events in long-term survivors.
  
  
  CONCLUSIONS
  Although the anterior oblique technique for treating early glottic cancers is well described, and it is predictable that the dose received by the carotid arteries should be lower with this technique, to our knowledge this is the first study to quantify that reduction in dose with a series of patients.
authors.affiliation: Department of Clinical Oncology, Christie Hospital, Manchester, UK.
authors.forename: K
authors.initials: K
authors.lastname: Garcez
authors.forename: C C
authors.initials: CC
authors.lastname: Lim
authors.forename: P
authors.initials: P
authors.lastname: Whitehurst
authors.forename: D
authors.initials: D
authors.lastname: Thomson
authors.forename: K F
authors.initials: KF
authors.lastname: Ho
authors.forename: M
authors.initials: M
authors.lastname: Lowe
authors.forename: A
authors.initials: A
authors.lastname: Sykes
authors.forename: L W
authors.initials: LW
authors.lastname: Lee
authors.forename: B
authors.initials: B
authors.lastname: Yap
authors.forename: N
authors.initials: N
authors.lastname: Slevin
mesh_terms: D002339:Carotid Arteries / Q000528:radiation effects*; D005260:Female; D005931:Glottis / Q000528:radiation effects*; D006801:Humans; D007822:Laryngeal Neoplasms / Q000532:radiotherapy*; D008297:Male; D011874:Radiometry; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted