title: 3D conformal radiotherapy for gastric cancer--results of a comparative planning study.
abstract: OBJECTIVE
  Many radiation oncologists are reluctant to use anteroposterior-posteroanterior (AP-PA) field arrangements when treating gastric cancer with adjuvant postoperative radiotherapy due to concerns about normal tissue toxicity, particularly in relation to the kidneys and spinal cord. In this report, we describe a multiple-field conformal radiotherapy technique, and compare this technique to the more commonly used AP-PA technique that was used in the recently reported Intergroup study (INT0116).
  
  
  METHODS
  Fifteen patients with stages II-IV adenocarcinoma of the stomach were treated with adjuvant postoperative chemoradiotherapy using a standardised 3D conformal radiotherapy technique that consisted of a 'split-field', mono-isocentric arrangement employing 6 radiation fields. For each patient, a second radiotherapy treatment plan was generated utilising AP-PA fields. The two techniques were then compared for target volume coverage and dose to normal tissues using dose volume histogram (DVH) analysis.
  
  
  RESULTS
  The conformal technique provides more adequate coverage of the target volume with 99% of the planning target volume (PTV) receiving 95% of the prescribed dose, compared to 93% using AP-PA fields. Comparative DVHs for the right kidney, left kidney and spinal cord demonstrate lower radiation doses using the conformal technique, and although the liver dose is higher, it is still well below liver tolerance.
  
  
  CONCLUSIONS
  3D conformal radiotherapy produces superior dose distributions and reduced radiation doses to the kidneys and spinal cord compared to AP-PA techniques, with the potential to reduce treatment toxicity.
authors.affiliation: Division of Radiation Oncology, Peter MacCallum Cancer Centre, St Andrews Place, East Melbourne, Vic. 3002, Australia.
authors.forename: Trevor
authors.initials: T
authors.lastname: Leong
authors.forename: David
authors.initials: D
authors.lastname: Willis
authors.forename: Daryl Lim
authors.initials: DL
authors.lastname: Joon
authors.forename: Sara
authors.initials: S
authors.lastname: Condron
authors.forename: Andrew
authors.initials: A
authors.lastname: Hui
authors.forename: Samuel Y K
authors.initials: SY
authors.lastname: Ngan
mesh_terms: D000230:Adenocarcinoma / Q000532:radiotherapy* / Q000601:surgery; D006801:Humans; D011832:Radiation Injuries / Q000517:prevention & control; D011874:Radiometry; D018714:Radiotherapy, Adjuvant; D020266:Radiotherapy, Conformal / Q000379:methods*; D013274:Stomach Neoplasms / Q000532:radiotherapy* / Q000601:surgery; D016896:Treatment Outcome