Abstract
Although the guideline edited by the Japanese Breast Cancer Society states that so far there are insufficient grounds for recommending ultrasonic examination as a method for breast cancer screening, it is simple, harmless, and good for dense breast tissue, and therefore its usefulness for screening has been checked by many institutions and groups. The Niigata Association of Occupational Health has nine complete medical checkup institutions throughout the whole of Niigata prefecture, where breast cancer screening has been carried out on applicants for mass occupational screening. In 1994, ultrasonic examination was added to inspection-palpation screening to improve screening quality, and then in 2000 mammography was further added for those who wanted to receive it. During the three-year period from 2007 to 2009, we intentionally tried to improve the quality of mass screening system, and good results were obtained, the breast cancer detection rate being increased from 0.17% to 0.22%. The rates of detection of early breast cancer by different screening modality were as follows: Among breast cancers detected by mammography alone, DCIS accounted for 35.7% and the rate of early breast cancer detection was 100%. On the other hand, of all cancers detected by ultrasonography alone, 15.8% were DCIS and 78.9% were Stage I invasive cancers, and so the rate for the two combined was 94.7%. This result shows that ultrasonography is useful for detection of small invasive cancers. In conclusion, each individual examination method has its own characteristic usefulness for detection of breast cancers, and it is hoped that the breast cancer death rate will be reduced through combined use of these different screening modality.
