The impact of virtual simulation in palliative radiotherapy for non-small-cell lung cancer

Background and purpose: Radiotherapy is widely used to palliate local sympt oms in non-small-cell lung cancer. Using conventional X-ray simulation, it is often difficult to accurately localize the extent of the tumour. We repo rt a randomized, double blind trial comparing target localization with conv entional and virtual simulation. Methods: Eighty-six patients underwent both conventional and virtual simula tion. The conventional simulator films were compared with digitally reconst ructed radiographs (DRRs) produced from the computed tomography (CT) data. The treatment fields defined by the clinicians using each modality were com pared in terms of field area, position and the implications for target cove rage. Results: Comparing fields defined by each study arm, there was a major mis- match in coverage between fields in 66.2% of casts, 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 fie lds, 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 def inition of the target volume. This could enable a reduction in geographical misses, while also reducing treatment-related toxicity. (C) 2001 Elsevier Science Ireland Ltd. All rights reserved.