Author: Mireille Conrad, Cédric De Marco, Marie Fargier-Voiron, Maud Jaccard, Oscar Matzinger, Nicolas Joel Lionel Perichon 👨🔬
Affiliation: Clinique De Genolier 🌍
Purpose: The Accuray Synchrony real-time motion fiducial tracking solution allows for prostate stereotactic treatment on both Cyberknife and Radixact machines. In our radiotherapy department, two solutions are currently available: Radixact treatments calculated with Raystation planning system and Cyberknife treatments calculated with Precision. We are about to switch to Raystation for both machines. Our aim is to find objective criteria to propose the optimal combination for patient treatment, focusing on dose distribution.
Methods: A comparative retrospective dosimetric study was performed on 10 patients treated on Cyberknife with 36.25 Gy in 5 fractions using these three configurations: Cyberknife with Precision plan (actual delivered plan), Radixact with Raystation plan, and Cyberknife with Raystation plan. To compare these clinically validated plans, dose constraints to organs at risk (OARs) defined in the PACE-B trial were used in combination with dose distribution metrics like new conformity and gradient index (GI). Additionally, an estimation of treatment time delivery given by the TPS was recorded.
Results: For each patient, all plans were normalized for having a 98% PTV coverage. Metrics from Cyberknife plans were not statistically different between Precision and Raystation. However, it appears that dose to rectal wall calculated for Radixact plans is significantly lower than the one for Cyberknife plans for V32.6Gy and V29Gy constraints. GI is significantly lower for Cyberknife and both planning systems compared to Radixact. Mean treatment times range from 10 min for Radixact to 25 min for Cyberknife.
Conclusion: In all cases PTV coverage and dose to OARs constraints given by PACE-B trial were achieved. Additional treatment plans should be calculated to enhance statistic of the study.
Decision to choose one of the systems should be taken considering other parameters: effective treatment time, tracking accuracy and modality of image-guided radiation therapy since Radixact machine enables acquisition of volumetric images.