Cellular and tumor radiobiology

With confluence cultures of the C3H10T1/2 cell line some studies have been initiated on the low-dose-rate effect of high-LET particles on cell transformation. Results show that there was no significant difference in cell killing between cells irradiated with low- and high-dose-rate iron particles (600 MeV/u; ∼200 keV/μm). For cell transformation, however, confluent cells irradiated with 2-rad/min iron particles gave a significantly higher transformation frequency than those irradiated with 100-rad/min iron beam. The enhancement effect was greater at lower doses than at higher doses. The transformation frequency of dose 175 rad of low dose rate was, however, no higher than that for 250 rad of high dose rate. These results, although preliminary, indicate that high-LET heavy ions may enhance cell transformation at low dose rate as fission neutrons