The well-established multiple step nature of carcinogenesis is linked to the occurrence of multiple genetic alterations. An awareness of the importance of viruses goes as far back as 1914 when Fujinami revealed the existence of a chicken sarcoma virus. Proof of a causative role was provided by the generation of stomach cancers by combined treatment with Helicobacter pylori and MNNG in Mongolian gerbils. Twelve points for cancer prevention, based on life style improvement, were previously proposed by the National Cancer Center, including balanced dietary habits. These are in agreement with the 15 points for cancer prevention recently issued by American Institute for Cancer Research.
Japan encourages early diagnosis by means of mass-screening and treatment of early stage cancer.