Radiation Risk Estimate and Risk-Benefit Analysis Following Breast Cancer Screening Using Mammography

1999 Fiscal Year Final Research Report Summary

• Project/Area Number: 10470192
• Research Category: Grant-in-Aid for Scientific Research (B)
• Allocation Type: Single-year Grants
• Section: 一般
• Research Field: Radiation science
• Research Institution: Oita University of Nursing and Health Sciences
• Principal Investigator: KUSAMA Tomoko Faculty of Nursing, Oita University of Nursing and Health Sciences, Professor, 看護学部, 教授 (50134523)
• Co-Investigator(Kenkyū-buntansha): AKAHANE Keiichi Faculty of Nursing, Oita University of Nursing and Health Sciences, Research Associate, 看護学部, 助手 (80202521) ; BAN Nobuhiko Faculty of Nursing, Oita University of Nursing and Health Sciences, Assistant Professor, 看護学部, 講師 (70251220) ; KAI Michiaki Faculty of Nursing, Oita University of Nursing and Health Sciences, Professor, 看護学部, 教授 (10185697)
• Project Period (FY): 1998 – 1999
• Keywords: MAMMOGRAPHY / BREAST CANCER RISK / MASS SCREENING / X-RAY / CR

Research Abstract

In Oita prefecture, we investigated whether screening mammography (SMG) is used for detecting early breast cancer, and found that SMG is carried our in 8 medical facilities among 14 facilities which preform primary mass screening. In each, the average does to breast tissue was less than 3mGy which is guidance level recommended by IAEA. However, there was large variation among the facilities. The Maximum dose was 4.25 time higher than the minimum. The doses may depended not only upon age at diagnosis but also a type of record in SMG, which the dose in film-screen record was 2.4 times higher than in CR (Computed Radiography).
Average glandular doses to breast were based on determination of entrance skin exposure (ESE) to the breast of a known thickness. The relation between the ESE and average glandular dose was obtained using the Monte Carla method with the EGS4 code. This method enables us to look at the effect of any breast composition.
We investigated the relation between the dose and the image quality in SMG using a RMI 156 phantom in order to optimize the breast dose. Image evaluation was carried out by 8 radiation technicians and one radiologist according to the guideline of the Japan Association of Breast Cancer Screening. The total evaluation of performance in CR was lower than in film-screen whereas the dose in film-screen record was 2.4 times higher than in CR. If the dose increase in CR, a better performance did not appear to be increased. The various factors which control the relation between the dose and the image quality will be need to make clear.
We analyzed breast cancer incidence data of atomic bomb survivors in Hiroshima and Nagasaki using a two-stage stochastic model and found that our model can explain the incidence trend due to birth cohort effect.