The mortality rate due to breast cancer has decreased in the USA, probably as a result of the spread of mammography screening. The incidence of breast cancer has also shown a further decrease recently, probably due to the decreased use of hormone replacement therapy (HRT). In contrast, both the mortality and incidence of breast cancer in Japan are increasing. Although the incidence rates of breast cancer in postmenopausal women are much lower than those in the USA or western countries, they have been increasing among postmenopausal Japanese immigrants in the USA. Therefore, it seems that potentially modifiable environmental and lifestyle risk factors, as well as female reproductive factors, have an important relationship to the incidence of breast cancer.
On the basis of global evaluation, there is convincing evidence that alcoholic drinks are a cause of breast cancer and that lactation has a protective effect against breast cancer. Greater body fatness probably protects against premenopausal breast cancer, while it is convincing to be a risk factor for postmenopausal breast cancer. Physical activity probably protects against postmenopausal breast cancer, but its relationship to premenopausal breast cancer still requires further study.
In Japan, there may be little impact of body fatness on breast cancer because of the very low prevalence rate of obesity. As only a very small proportion of Japanese women drink alcohol daily, the potential of alcohol as a risk factor for breast cancer is difficult to evaluate. Although there is little doubt that physical activity is good for health, there is limited evidence that it protects against breast cancer. It is possible that isoflavone, which is consumed regularly as part of the diet in Japan throughout life, protects against breast cancer especially in postmenopausal women. Also, there is some evidence that not only passive smoking, but also smoking, is a cause of breast cancer especially among premenopausal Japanese women.

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Although medical services aimed at prevention of breast cancer are limited in Japan, prophylactic surgery (bilateral oophorectomy or bilateral mastectomy), chemoprevention(tamoxifen or raloxifene), and periodic screening are common in western countries. A study of 1,383 women with a mutation of BRCA1 or BRCA2 before breast cancer diagnosis showed that 18.0% had undergone bilateral prophylactic mastectomy and 49.2% had undergone bilateral prophylactic oophorectomy. In that study, 5.5% of women who did not undergo mastectomy took tamoxifen, and 2.9% took raloxifene. In the United States, tamoxifen was approved for breast cancer prevention in 1998 and raloxifene in 2007. A double-blind randomized controlled trial for postmenopausal women with a high risk demonstrated that raloxifene was similarly effective in terms of breast cancer prevention, with lower risks of endometrial cancer, thrombosis, and cataract than tamoxifen. Raloxifene has been approved as an anti-osteoporosis drug in Japan. Breast cancer prevention using either drug is not covered by the medical insurance system in Japan, resulting that its prescription is rare. Tamoxifen is activated by CYP2D6 and raloxifene is metabolized by UGT1A1. It is known that the activity of both enzymes is determined by the genotype for each enzyme. Therefore, genotyping of these genes will be an option for breast cancer prevention.

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Recently, the age-adjusted incidence and death rate of breast cancer have been increasing in Japan, and the establishment of primary and secondary prevention strategies is becoming important. The age-specific incidence rate of breast cancer in Japan shows characteristic features in comparison with Euro-American countries. The peak age at onset of breast cancer is around 50 years, and more than 65% of breast cancer patients in Japan are distributed within the 40-65-year age range. The 5-year survival rate for breast cancer is relatively good, and a rate of almost 100% might be expected if early detection and treatment were possible. In order to reduce not only the death rate but also medical costs, it is necessary to promote effective screening programs to detect breast cancer at an early stage. On the other hand, general risk factors for breast cancer have been clarified by previous epidemiological studies, and middle-aged women with such risk factors, e.g., a family history of breast cancer, benign breast tumor, obesity (BMI>25), early menarche or later menopause, unmarried or nulliparous, etc. should undergo breast cancer screening more frequently. Finally, a primary prevention strategy involving improvement of general lifestyle, e.g., more daily exercise and a well balanced diet, is also important for reducing both the incidence of breast cancer and the associated death rate.

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Objective: We assessed the usefulness of telemammography by soft-copy diagnosis.
Methods: A wide area network for teleradiology was set up incorporating seven institutions located in two prefectures. A total of 1053 subjects were enrolled. The first reading was performed using hard-copy images at the institution where mammography was undertaken. The second reading using hard-copy images was then performed. These images were transferred to our institution, where a second reading based on soft-copy images was performed. The result of soft-copy diagnosis were then compared with those of the hard-copy diagnosis. The diagnosis concordance rate, which was higher than category 3, was evaluated.
Results: Category 1 or 2 accounted for 956 cases at the stage of the second hard-copy diagnosis, of which category 1 or 2 accounted for 930 cases analyzed in the second soft-copy diagnosis. A category higher than 3 accounted for 97 cases at the second hard-copy diagnosis, of which a category higher than 3 accounted for 75 cases at the stage of the second soft-copy diagnosis. The κ-value for the diagnosis concordance rate was 0.751.
Conclusion: The diagnostic concordance between hard-copy diagnosis and soft-copy diagnosis was good. Diagnostic accuracy showed no significant difference between the two. We conclude that soft-copy diagnosis by telemammography is useful, and that its application is desirable for screening mammography.

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To evaluate the influence of soft-copy reading for digital mammography when switching from hard-copy reading, we examined the recall rate, positive predictive value (PPV), and cancer detection rate for population-based mass screening in Miyagi prefecture. There was no significant difference in the recall rate for mass-finding. In cases showing calcification, the recall rate for hard-copy reading and soft-copy reading was 0.84% and 0.67% respectively, and the difference was significant (p=0.01). On the other hand, for other findings, the recall rate for soft-copy reading (1.50%) was significantly higher than that for hard-copy reading (1.02%). There was no significant difference in the cancer detection rate between hard-copy and soft-copy reading, although a high recall rate for other findings was the prime cause of the low PPV for hard-copy reading.

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The system for mammographic reading has been undergoing a change from a hard-copy to a soft-copy system, and it is necessary to ensure that the reading performance is not decreased as a result. Therefore, we have been prospectively studying the performance of radiologists to determine how they read soft-copy (SC) and hard-copy (HC) data from the same cases. The information obtained using monitors is limited by resolution and contrast. In this study, 5,787 screening mammograms were prospectively read for each system by 16 radiologists certified as Grade A by the Central Committee for Quality Control of Mammography Screening in Japan. The recall and detection rates were 5.3% and 0.17% for HC, and 6.7% and 0.16% for SC. Calcification was detected more sensitively by SC than by HC, because of the magnification methods employed. The degrees of mass and distortion were almost the same. Persons in whom FAD was found and/or FAD location in the breast were different between SC and HC.
We conclude that reading performance does not differ significantly between SC and HC, but that SC requires more time for picking up details.

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The number of women participating in breast cancer screening in Kyoto City was 19,093 in 2007,and the participation rate of 8.6% was less than the national average (12.9%) in 2006. The number of examinees attending our Kyoto Preventive Medical Center was 4,322 in 2007. Since 60-70% of women of their 5th to 6th decades in Kyoto City have occupations, it is very important to maintain the system of screening of the working population, for which new legislation will be necessary.
Although, for quality control of breast cancer screening for inhabitants in Kyoto City, a regional hub has been advocated, recall responders have often visited institutions other than our center, leading to incomplete follow-up. Problems have also been created due to Personal Information Protection Law and the duty of confidentiality of medical doctors, highlighting the need for revision of the related laws.
In their responses to our questionnaires, many of the examinees expressed a wish for female doctors or radiological technologists to conduct the screening examinations. Therefore, the presence of more female doctors at screenings, and for carrying out inspection and palpation, might improve the participation rate. Some examinees underwent inappropriate examinations, such as those involving only inspection and palpation, or those involving mammography for women in their 20s. It was thought that breast cancer screening might be promoted further if it was included among the items in annual occupational health checks. A need to reconsider the present system, in which companies or health insurance associations have different kinds of health check items for examinees (or their husbands), was also indicated.
Women's lifestyles vary according to marriage, childbirth, child care, and mode of work. In order for all women to have equal access to proper and effective health care services, they must be aware of the services that are appropriate for various stages of their lives and the importance of preventive care for various diseases, including breast cancer screening.

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To investigate the characteristics of full-field digital mammography (FFDM) in comparison with screen film mammography (SFM), we compared the results of interpretation between FFDM and SFM in 64 patients with breast carcinoma who were preoperatively examined using both modalities. In FFDM, the flat panel detector was adopted, and double reading was performed using a 5-megapixel liquid crystal display monitor. The mass margins, associated findings such as architectural distortion or micro-calcification, and categories were compared. Identification of the lesion was difficult in 7.8% of cases by FFDM and in 10.9% by SFM. The category was 4 or 5 in78.2% by FFDM and in 70.3% by SFM; diagnosis was more accurate using FFDM. The mass margins were microlobulated or spiculated, being highly specific to cancer, in 65.7% of cases by FFDM and in 45.7% by SFM, allowing more detailed diagnosis by FFDM. Associated findings were revealed in 59.4% of cases by FFDM but in only 45.3% by SFM. Isodense DCIS without associated findings accounted for 60% of the lesions not identified by FFDM, while small invasive carcinoma accounted for 85.7% of those not identified by SFM. FFDM was superior to SFM in its ability to detect invasive carcinoma affecting survival.

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[in Japanese]

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