Whole Breast and Lymph Node Irradiation using Halcyon™ 2.0 Utilizing Automatic Multi-isocenter Treatment Delivery and Daily Kilovoltage Cone-beam Computed Tomography

The Halcyon(TM) is a newly introduced platform to provide a simplified high-throughput workflow. A substantial fraction of patients treated with radiation are receiving breast irradiation. The Halcyon has a smaller maximum field size (28 x 28 cm(2)) compared to traditional C-arm linacs, limiting treatment of larger breast fields. With the use of autofeathering and linked multiple isocenters, non-divergent beams can be used to treat whole breast with large mid-tangent separation. In this case report, a multiple isocenter whole breast treatment with nodal involvement is described with the Halcyon 2.0 platform. The patient was simulated with the same immobilization techniques as used for C-arm linac treatments. The treatment planning time was around 20-30 minutes, which is similar to traditional planning for C-arm linacs, and dosimetric analysis resulted in satisfactory dose-volume histogram (DVH) parameters that met all planning objectives. Treatment times were shorter with an average of 9:32 minutes from the beginning of imaging to the end of treatment and a total in-room time of around 15 minutes per fraction. The use of multiple isocenters for the extended treatment field created a half-beam block type field arrangement, which has been previously reported to produce superior dosimetry results at the supraclavicular-tangents junction area