Response of plateau-phase cultures and multicellular spheroids of human osteosarcoma cells to carbon beam irradiation

The possible therapeutic advance in achieving local tumor control using high LET radiation therapy is the major area of interest to clinical radiation oncologists and radiobiologists. This includes improved depth dose distribution, greater relative biological effectiveness (RBE) and the greater reduction of oxygen enhancement ratio (OER). In addition, the type of damage produced by charged particles is less amenable to repair. Mammalian cells repair radiation damage by sublethal damage (SLD) repair and potentially lethal damage (PLD) repair. Because the recovery from PLD might significantly contribute to the ultimate therapeutic response of a solid tumor, the ability of plateau phase osteosarcoma cells to recover from PLD after the irradiation with RIKEN ring cyclotron-accelerated carbon ions in the spread-out Bragg peak (SOBP) region was investigated. Also the relation of dose to cure probability for the spheroids of osteosarcoma cells after the irradiation with carbon beam in the SOBP was measured. The materials used, the experimental method and the results are reported. The dose response curves measured and the dose-cure probability relation are given. (K.I.)