Left breast cancer patients who visited our institution from November 2014 to April 2015 were included in this study. Among them, 20 patients were randomly selected and further investigated. Before simulation computed tomography (CT), whole breast tissue of each patient was wired using radio-opaque material. Simulation CT was performed using a LightSpeed RT16 CT scanner (GE Healthcare, Waukesha, WI) with 2.5 mm thickness. When simulation CT was conducted, all patients used a vac-lock immobilization device with a 10 degree tilted breast board. Eclipse version 8.9 (Varian Medical Systems, Palo Alto, CA) was used as a radiation treatment planning system.
The planning target volume (PTV) of the left breast, heart, left ventricle, both lung, and spinal cord were delineated. To evaluate the dose delivered to the skin, 2 mm thickness skin (2-mm skin) and 3 mm thickness skin (3-mm skin) were also contoured. The average volume of PTV was 453.6 cm3 (range: 180.1 to 761.4 cm3). For the consistency of target volume and OARs, all of these were contoured by a single experienced radiation oncologist. The PTV was based on the RTOG atlas [12 ]. However, the PTV was edited according to the wired area, surgical clip, and seroma, and we trimmed the anterior border by 3 mm from the skin for skin-sparing treatment planning.
The planning target volume (PTV) of the left breast, heart, left ventricle, both lung, and spinal cord were delineated. To evaluate the dose delivered to the skin, 2 mm thickness skin (2-mm skin) and 3 mm thickness skin (3-mm skin) were also contoured. The average volume of PTV was 453.6 cm3 (range: 180.1 to 761.4 cm3). For the consistency of target volume and OARs, all of these were contoured by a single experienced radiation oncologist. The PTV was based on the RTOG atlas [12 ]. However, the PTV was edited according to the wired area, surgical clip, and seroma, and we trimmed the anterior border by 3 mm from the skin for skin-sparing treatment planning.