Revision 1
March 19, 1998
by Radiation, Science, and Health, Inc.,
Edited by J. Muckerheide

1.2.3
Medical

1.2.3.2
Medical Patients

" ‘Analyses of the incidence of breast cancer among Japanese atomic-bomb survivors have indicated that the dose-response curve is essentially linear (Tokunaga et al. 1987) (Table 3.2). The low-dose portion of the data set has also been examined. In the irradiated group with <0.5 Gy, 179 breast cancers were observed as compared with 163 expected. A statistically significant dose-response trend was seen over the range 0.2 to 0.5 Gy, and the trend was suggestive, but not statistically significant for the dose range up to 0.2 Gy.

‘There was a significant dose-response relationship which was consistent with linearity. There was also a significant elevation of risk in the subgroup who received less than 0.5 Gy.

‘The 2,500 women in this cohort received an average breast dose of 0.8 Gy from an average of 88 fluoroscopic examinations. The risk estimate for this highly fractionated protocol was comparable in magnitude to those from studies with unfractionated exposures (Table 3.2), and the dose-response relationship was well approximated by a simple linear model.

"Similar results were found in a large multiple fluoroscopy study of 31,700 women in Canada (Miller et al. 1989) where it was reported that a linear dose-response provided a good fit with a risk estimate comparable with other breast-irradiation studies. An excess was evident over the entire dose range, including doses below 0.4 Gy.

‘The data are supportive of an interpretation that low doses or fractionated doses have a substantial degree of additivity of their effects upon breast cancer risk.

‘The data for breast cancer from x-ray irradiation, perhaps more than any other human cancer, supports the notion of a dose-response relationship that is a linear function of dose and largely independent of dose rate or fractionation, thus supporting the concept of collective dose.’" [Emphasis added.]