[The potential of cancer prevention]

Cancer prevention is an important cancer control strategy. It consists of primary and secondary cancer preventions. The former aims to prevent cancers by removing risk factors and supplementing protective factors. The latter aims to prevent cancer deaths by early detection-early treatment through periodic screening. The potential of cancer prevention in Japan was estimated statistically based on available data and assumptions. The main results obtained from the present estimation were as follows: 1) about 9-10% of cancers could be prevented if prevalence of adults smoker decreased to a half of the present level; 2) about 8-10% of cancer could be prevented by the improvement of dietary habits; reduction of salt intake and avoidance of excess intake of fats; 3) another 1-5% could be prevented by prevention of hepatitis B virus infection and improvements of work environment and air pollution; 4) a total of about 18-25% could be prevented if primary prevention is promoted extensively; 5) about 10-13% of cancer deaths could be prevented if periodic screenings for stomach cancer, cervical cancer, breast cancer, lung cancer and large intestinal cancer are widely conducted and the coverage rate of these cancer screenings reach to 30%; 6) a total of about 30-40% of cancer incidence/deaths could be prevented if both of primary and secondary preventions are promoted extensively in Japan. It is considered necessary to improve these estimates after considering time factors in primary cancer prevention and biases inherent to cancer screening in secondary cancer prevention.