On the need of in vivo verifcations as quality control for intraoperative electron radiotherapy in breast cancer

• Carla Cases ^[1] ; Gabriela Oses ^[1] ; Antonio Herreros ^[1] ; Jordi Tarrats Rosell ^[1] ; Sara Moreno ^[1] ; Meritxell Mollà ^[1]
  1. [1] Department of Radiation Oncology, Hospital Clínic, Carrer de Villarroel 170, 08036 Barcelona, Spain
• Localización: Clinical & translational oncology, ISSN 1699-048X, Vol. 26, Nº. 7, 2024, págs. 1623-1629
• Idioma: inglés
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• Resumen

  • Introduction Intraoperative electron radiotherapy (IOERT) is a technique aiming to deliver radiotherapy during oncological surgery. In breast IOERT, the applicator and shielding disc placement are correlated with organs at risk (OAR) irradiation, in vivo verifcation of these parameters is scarcely reported. The aim of our study is to report and analyze possible causes of the misalignment using radiochromic flms and compare our results to others reported in the bibliography.

    Methods From November 2019 to April 2023, in vivo verifcations were performed for 33 patients. IOERT was performed using a LIAC 10 MeV (Sordina, Italy) electron accelerator. We attached a radiochromic flm to the upper side of the polytetrafuoroethylene cover of the shielding disc. The percentage of the irradiation area outside the disc was recorded and various parameters (applicator angulations, prescription depth, tumor location and breast size) were analyzed to fnd possible correlations.

    Results For 29 patients, 20 Gy were prescribed while 10 Gy were prescribed to 4 patients. The average irradiated area outside the disc was 19% (0–56%) corresponding to a surface of 4.5 cm2 (0–17.4 cm2). The applicator of 5 cm was used for most of the patients. The mean prescription depth was 1.4 cm (0.5–2.5 cm). We found no correlation between the analyzed parameters and misalignment.

    Conclusion This study confrms the presence and magnitude of the misalignments. We strongly recommend in vivo verifcations as a quality check during IOERT procedures. The misalignment has no correlation with tumor localization parameters, so the solution could be based on technical improvements of the applicator.