Abstract
Radiotherapy is one of the major therapeutic modalities for eradicating malignant tumors. Standard radiotherapy for tumor treatment consists of approximately 2 Gy once a day, 5 days a week, over a period of 5-8 weeks. However, the existence of radioresistant cells remains one of the most critical obstacles in radiotherapy. Therefore, we clarified the radiosensitivity of heavy-ion beams in X-ray resistant cells.
We used clinically relevant X-ray-resistant SAS-R cells from human tongue cancer SAS cells. The SAS and SAS-R cells were exposed to X-rays (TITAN-225S, Shimadzu) or carbon-ion beams (290 MeV/u, 6 cm-SOBP, Gunma University Heavy Ion Medical Center). We examined the cell survival after irradiation by modified high-density survival assay by scoring the total number of surviving cells using cell counter (TC10, BIO RAD).
Our results show that 20% survival dose of X-rays were 7.5 and 12 Gy in SAS cells and SAS-R cells, respectively. The 20% survival dose of carbon-ion beams were 3.0 and 3.2 Gy in SAS cells and SAS-R cells, respectively. Relative biological effectiveness (RBE) at 20% survival in SAS cells and SAS-R cells was 3.8 and 2.5, respectively. It is suggested that heavy-ion beams are useful in cancer therapy.
