Differences in Linear Energy Transfer Affect Cell-killing and Radiosensitizing Effects of Spread-out Carbon-ion Beams.

Objective: The cell-killing and radiosensitizing effects of carbon-ion (C-ion) beams with low linear energy transfer (LET) are underexplored. We aimed to demonstrate the cell-killing effects of 60Co gamma rays and C-ion beams at various LET values and the radiosensitizing effect of C-ion beams at various LET and cisplatin levels.

Methods: Human uterine cervical cancer cells were irradiated with 60Co gamma rays and C-ion beams at different levels of LET, with and without cisplatin treatment.

Results: Low-LET C-ion beams had a superior cell-killing effect compared to 60Co gamma rays. Survival curves under low-LET C-ion beams were more similar to that of 60Co gamma rays than that of high-LET C-ion beams. Cisplatin significantly reduced cell survival after 1, 2, and 3 Gy C-ion beam irradiations at LET values of 13/30/70 keV/μm, 13/30 keV/μm, and 13 keV/μm, respectively.

Conclusions: Low-LET C-ion beams combined with cisplatin have higher radiosensitizing effects than high-LET C-ion beams.