The impact of virtual simulation in palliative radiotherapy for non-small-cell lung cancer.
OBJECTIVE
Radiotherapy is widely used to palliate local symptoms in non-small-cell lung cancer. Using conventional X-ray simulation, it is often difficult to accurately localize the extent of the tumour. We report a randomized, double blind trial comparing target localization with conventional and virtual simulation.


METHODS
Eighty-six patients underwent both conventional and virtual simulation. The conventional simulator films were compared with digitally reconstructed radiographs (DRRs) produced from the computed tomography (CT) data. The treatment fields defined by the clinicians using each modality were compared in terms of field area, position and the implications for target coverage.


RESULTS
Comparing fields defined by each study arm, there was a major mis-match in coverage between fields in 66.2% of cases, and a complete match in only 5.2% of cases. In 82.4% of cases, conventional simulator fields were larger (mean 24.5+/-5.1% (95% confidence interval)) than CT-localized fields, potentially contributing to a mean target under-coverage of 16.4+/-3.5% and normal tissue over-coverage of 25.4+/-4.2%.


CONCLUSIONS
CT localization and virtual simulation allow more accurate definition of the target volume. This could enable a reduction in geographical misses, while also reducing treatment-related toxicity.
McJury
M
M
Department of Radiotherapy Physics, Weston Park NHS Trust, Whitham Road, S10 2SJ, Sheffield, UK.
Fisher
P M
PM
Pledge
S
S
Brown
G
G
Anthony
C
C
Hatton
M Q
MQ
Conway
J
J
Robinson
M H
MH
D002289:Carcinoma, Non-Small-Cell Lung / Q000532:radiotherapy*; D003198:Computer Simulation / Q000706:statistics & numerical data*; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods; D008175:Lung Neoplasms / Q000532:radiotherapy*; D008962:Models, Theoretical; D010166:Palliative Care; D015203:Reproducibility of Results; D016896:Treatment Outcome; D014584:User-Computer Interface