The current practice of volumetric modulated arc therapy for breast cancer in Europe - A survey by the EFOMP VMAT breast working group

Introduction VMAT is used in the treatment of breast cancer with a wide variety of approaches. The objective of this study is to identify and share the most common indications, techniques, and practices for the use of VMAT for breast irradiation. Methods The EFOMP VMAT Breast working group conducted an online questionnaire for European medical physicists via EFOMP national member organizations in February-March 2024. The questionnaire consisted of 56 questions in six categories: background of responders; treatment site specific approaches; dosimetric principles; treatment planning; quality assurance; and foundation of the VMAT breast technique used. Results A total of 314 responses were analyzed from various institutes across 31 countries, representing approximately 20 % of European radiotherapy centers. Of these, 73 % use VMAT for breast radiotherapy. Among the VMAT users, VMAT is most often used for more complex treatment sites, such as breast with lymph nodes and the internal mammary chain (56 % of responders). Most of these treatments are performed with C-arm linacs (77 %), using daily IGRT (>80 % of institutes) with CBCT (>50 %) as the preferred technique. Across all treatment sites, VMAT breast treatments are most often implemented with two arcs, an arc length of >150 degrees, 5 mm CTV-to-PTV margin and skin/auto flash of 10 mm. Conclusion This paper presents a comprehensive survey of VMAT breast radiotherapy in Europe. These data can serve as a useful reference point or starting guide for centers establishing VMAT protocols.