1. Department of Radiation Oncology, National Hospital Organization Shikoku Cancer Center, Matsuyama, Ehime 791‑0280, Japan
2. Department of Radiation Oncology, Saiseikai Imabari Hospital, Imabari, Ehime 799‑1592, Japan
3. Department of Radiology, Ehime University Graduate School of Medicine, Toon, Ehime 791‑0295, Japan
4. Department of Breast Oncology, National Hospital Organization Shikoku Cancer Center, Matsuyama, Ehime 791‑0280, Japan