Benefits and limitations of volumetric modulated arc therapy in treating bilateral breast cancer with regional lymph nodes

Purpose: The study was performed comparing dosimetric characteristics ofvolumetric modulated arc therapy (VMAT) and field-in-field (FiF) techniques on a patient with synchronous bilateral breast carcinoma. Methods:The patients with bilateral breast cancer treatment were included in thisstudy. A total dose of 40.05 Gy in 15 fractions was prescribed to the PlanningTarget Volume (PTV) of the whole bilateral breast cancer with the supraclavicular and infraclavicular nodes, with a complementary boost of 10 Gy in 4fractions to the surgical bed (PTVboost). For both radiotherapy techniques,several VxGy parameters were analyzed for the PTVs, together with the Conformity index (CI), the Homogeneity index (HI) and the critical organs atrisk (OARs), lungs and heart. Results: The patient was treated by the VMATtechnique and the daily treatment time was less than 20 minutes with dailyCBCT imaging. In the VMAT plan, the PTV 95% dose covered 38.89 ± 0.81Gy, compared to 37.26 ± 1.02 Gy in the FiF technique. The VMAT plan improved the dose homogeneity index and lower dose in lung towards high doseregion. Conclusion: The study demonstrates the viability of the VMAT technique in the treatment of bilateral breast cancer. The introduced single isocentric VMAT technique is fast to deliver and it increases the dose homogeneity of the target volume with some limitations. The treatment was welltolerated, without interruption of the treatment courses caused by treatmentrelated toxicities.