Meta-analysis of non-tumour doses for radiation-induced cancer on the basis of dose-rate

Purpose: Quantitative analysis of cancer risk of ionising radiation as a function of dose-rate. Materials and methods: Non-tumour dose, D(nt), defined as the highest dose of radiation at which no statistically significant tumour increase was observed above the control level, was analysed as a function of dose-rate of radiation. Results: An inverse correlation was found between D(nt) and dose-rate of the radiation. D(nt) increased 20-fold with decreasing dose-rate from 1-10(-8) Gy/min for whole body irradiation with low linear energy transfer (LET) radiation. Partial body radiation also showed a dose-rate dependence with a 5- to 10-fold larger D(nt) as dose rate decreased. The dose-rate effect was also found for high LET radiation but at 10-fold lower D(nt) levels. Conclusions: The cancer risk of ionising radiation varies 1000-fold depending on the dose-rate of radiation and exposure conditions. This analysis explains the discrepancy of cancer risk between A-bomb survivors and radium dial painters.