Abstract
In Japan, mammography together with physical examination is scheduled to be introduced for mass screening of breast cancer instead of physical examination only. The first step is to clarify that the benefit of mammography screening exceeds the risk of radiation exposure. The purpose of this study was to compare life-years saved by mammographic screening with corresponding life-years lost by radiation-induced cancer. A mathematical model was used to calculate net life-years saved by screening at 1-year and 2-year intervals using various parameters such as the sensitivity and specificity of mammography screening and the survival rates of screen-detected patients and outpatients. The risk was estimated using the radiation dose delivered to the mammary gland, risk coefficient for breast cancer/unit radiation dose, and years of life expectancy lost by induced cancer. Results of the comparison showed that the benefit was 50 times greater than the risk for 50-year-old women screened with a 2-year interval and a radiation dose of 3 mSv. It was also shown that benefit/risk ratios increased rapidly with age. Thus we may conclude that mammographic screening at 2-year intervals can be justified on the basis of benefit-risk analysis for women aged over 50 yr. However, further follow-up study is necessary in order to obtain more precise data for benefit analysis, and a quality control system should be established for monitoring the mammography radiation dose.
