Observational validation study of dosimetry using radiographic films in breast cancer intraoperative radiotherapy

Abstract

Background and purpose: Intraoperative radiotherapy (IORT) for breast cancer offers a promising alternative to conventional external beam radiotherapy by delivering high-dose radiation directly to the tumor bed during surgery. However, accurate dosimetry is critical to ensure the safety and efficacy of this procedure. This study aimed to develop and validate a reliable dosimetry using GAFchromic EBT-3 films for precise in vivo and in vitro dosimetry during IORT. The primary objective was to verify the accuracy of absorbed delivered doses during IORT using GAFchromic EBT-3 films, in comparison with that of Monte Carlo simulations.

Methods: This observational study included 38 patients with breast cancer who underwent IORT at Kaohsiung Municipal Ta-Tung Hospital and Kaohsiung Medical University Chung-Ho Memorial Hospital in Taiwan. Patients were selected based on predefined inclusion criteria. Using GAFchromic EBT-3 films during IORT, absorbed doses, including the applicator surface, excision wound, and surrounding breast tissue, were measured at various critical points. Monte Carlo simulations were conducted to validate the accuracy of these manufacturer-provided data.

Results: The mean measured dose was 20.37 ± 0.67 Gy, which had a 1.2 % discrepancy from the planned dose of 20 Gy. Dose measurements at other surrounding tissues indicated effective protection, with mean doses of 1.36 ± 0.92 Gy on the excision wound and 1.08 ± 1.18 Gy on the surrounding breast edge. Monte Carlo simulations confirmed a high level of consistency with the manufacturer's data, with an error margin of <3 %.

Conclusions: The use of GAFchromic EBT-3 films for dosimetry during IORT was feasible and reliable and provided an independent verification method to ensure accurate dose delivery. This study demonstrates that accurate dosimetric validation supports the clinical optimization of intraoperative radiotherapy (IORT), enabling precise dose delivery while reducing exposure to surrounding healthy tissues. These findings may contribute to enhanced treatment safety, improved local control, and favorable cosmetic outcomes in breast-conserving therapy. Further research is warranted to refine this technique and explore its applicability in other radiotherapy contexts.

Keywords: Breast conservation surgery; Dosimetry; Dosimetry error; GAFchromic film; Radiotherapy; Radiotherapy dose.