A retrospective comparison of two different immobilization systems for radiotherapy of extremity soft tissue sarcomas and its influence on CTV-PTV margin

Abstract Background On account of extremity wide range movements and difficulty reproducibility during irradiation sarcomas, assorted immobilization strategies are employed to eliminate setup errors. The study purpose was compare the errors commonly used tools define planning target volume (PTV) margins for each device. Methods A retrospective review comparing Vac-Loc™ thermoplastic cast (Tcast) conducted. radiotherapy treatment, portal imaging matched with pre-treatment simulation both fixation tools. isocenter shifts total vector error (TVE) were compared. Random (σ) systemic (Σ) computed PTV defined. Results Three hundred seven in direction measured 14 patients. Mean displacements Tcast, respectively, as follow: vertical; -0.01 cm vs. 0.02 cm, longitudinal; 0.03 0.04; lateral; 0.04 0.00 TVE; 0.15 0.17 no significant statistical difference. comparable devices. lateral displacement rotational random higher compared Tcast. Overall marginally lower Tcast Vac-Loc™. Conclusion valid options clear superiority either marginal advantage warrants further prospective studies.