Effects of Split-dose Irradiation on Survival and Oncogenic Transformation Induced by 31 MeV Protons in C3H10T1/2 Cells

Summary

Survival and oncogenic transformation were studied in C3H10T1/2 cells exposed to 31 MeV protons. Total doses of 0·5, 1 and 7 Gy were delivered as single and two equal fractions with various time intervals up to 10 h between doses. With split doses as compared with single doses to a total dose of 7 Gy, survival increased by a factor of 2·5 ± 0·2, whereas the frequency of transformation per surviving cell declined by a factor of 3·1 ± 0·5. Maximal split-dose recovery occurred within the first 5 h for both endpoints. Further, the transformation frequency decreased by factors of 3·1 ± 0·6 and 1·5 ± 0·3 respectively for total doses of 0·5 and 1·0 Gy split into two equal fractions. The data for 1 and 7 Gy are compatible with data in the literature for other low LET radiations.