Individualising radiation cancer risk: insights from animal studies.

Individual factors can affect the risk of radiation-related cancer. This article presents the key findings of an ongoing systematic review in Task Group 111 on the modification of radiation cancer risk in animals, including the author's recent reports on rat breast cancer. The results indicate that early age at exposure is associated with a high risk of cancer in most organs, with some variability. For example, there is a peak of susceptibility during the peripubertal period regarding rat breast cancer. Females are more susceptible regarding the risk of all tumours. Smoking, diet-induced overweight, parity, hormones, chronic inflammation, and exposure to chemicals modify the risk of leukaemia and solid cancers in exposed animals. Radiation interacts with a high corn oil diet and mutagenic chemicals in supra-multiplicative and multiplicative manners, respectively, regarding breast cancer in rats. Genetic evidence indicates significant impacts of strain and genetic defects relevant to human tumour syndromes and DNA repair. There has been a reported quasi-multiplicative interaction with strain regarding rat breast cancer, as well as an increased risk associated with a Brca1 variant. These findings demonstrate diverse interactions between radiation and different modifiers, emphasising key areas for epidemiology and the integration of biology and epidemiology.