3D conformal radiotherapy for gastric cancer--results of a comparative planning study.
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.
Leong
Trevor
T
Division of Radiation Oncology, Peter MacCallum Cancer Centre, St Andrews Place, East Melbourne, Vic. 3002, Australia.
Willis
David
D
Joon
Daryl Lim
DL
Condron
Sara
S
Hui
Andrew
A
Ngan
Samuel Y K
SY
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