The most significant risk of radiation is cancer development, resulting in the increase in age-specific mortality and the shortening of life expectancy. Since the largest increase in cancer risk in human with obesity was seen for liver cancer, calorie restriction (CR) has emerged as the most potent acting dietary intervention for suppressing hepatocarcinogenesis. In order to estimate anti-cancer effect of CR, B6C3F1 mice were irradiated at 1-week or 10-weeks-old. From 7-week-old, mice were divided into CR (65 kcal/week) and ad libitum (AL, 95 kcal/week) groups. All mice examined histologically for cancer incidence at death. We found that 1-week-old-irradiated mice with AL diet were most susceptible to radiation-induced liver tumor. As the effect of CR that started from 7-weeks-old, both tumor incidence reduction and life span extension were confirmed. Delayed cancer development was detected in sham-irradiated and 10-weeks-old-irradiated groups too. Our results suggest that CR from 7-weeks-old is effective against radiation-induced liver tumor especially after exposure at 1-week-old, indicate that CR is arguably the most useful remedy to prevent radiation-induced cancer.The 70th annual meeting of the Japanese Cancer Associatio
