Comparison of conventional and virtual simulation for radiation treatment planning of prostate cancer.

PURPOSE: radiotherapy is widely used to treat patients with prostate cancer. Using conventional x-ray simulation is often difficult to accurately localize the extent of the tumor, to cover exactly the lymph nodes at risk and shield the organs at risk. We report the initial results of a study conducted to compare target localization with conventional and virtual simulation. METHODS: fifty patients with prostate cancer underwent target localization for radical prostate radiotherapy using conventional and virtual simulation. The treatment fields were initially marked with a conventional portal film on LINAC, plain x-ray film and available diagnostic imaging. Each patient then had a computed tomography (CT) and these simulated treatment fields were reproduced within the virtual simulation planning system. The treatment fields defined by the clinicians using each modality were compared in terms of field area and implications for target coverage. RESULTS: there was significantly greater clinical tumor volume coverage using virtual simulation compared with conventional simulation and less normal tissue volume irradiated (p<0.001). CONCLUSION: CT localization and virtual simulation allow for more accurate definition of the clinical target volume. This could enable a reduction in geographical misses, while also reducing treatment-related toxicity.