BREAST-CANCER MORTALITY BETWEEN 1950 AND 1987 AFTER EXPOSURE TO FRACTIONATED MODERATE-DOSE-RATE IONIZING-RADIATION IN THE CANADIAN FLUOROSCOPY COHORT STUDY AND A COMPARISON WITH BREAST-CANCER MORTALITY IN THE ATOMIC-BOMB SURVIVORS STUDY
Gr. Howe et J. Mclaughlin, BREAST-CANCER MORTALITY BETWEEN 1950 AND 1987 AFTER EXPOSURE TO FRACTIONATED MODERATE-DOSE-RATE IONIZING-RADIATION IN THE CANADIAN FLUOROSCOPY COHORT STUDY AND A COMPARISON WITH BREAST-CANCER MORTALITY IN THE ATOMIC-BOMB SURVIVORS STUDY, Radiation research, 145(6), 1996, pp. 694-707
The relationship between exposure to low-linear energy transfer ionizi
ng radiation and subsequent breast cancer mortality risk is reported b
ased on a further 7 years of follow-up in the Canadian fluoroscopy stu
dy. Amongst 31,917 women first treated for tuberculosis in a Canadian
institution between 1930 and 1952, a total of 688 breast cancer deaths
were observed between 1950 and 1987. There is a strong linear trend o
f increasing risk with increasing dose (P < 0.0001), with the excess r
elative risk per sievert decreasing with age at exposure (P = 0.0003).
The excess relative risk is approximately constant between 5 and 39 y
ears after exposure, with a suggestion of a decrease between 40 and 57
years after exposure, though this could be a chance effect (P = 0.22)
. Combined analyses of the Canadian fluoroscopy data and the data for
the atomic bomb survivors with respect to breast cancer mortality are
also reported. In general the two studies are reasonably consistent, t
he only distinct difference being the much greater excess relative ris
k per sievert amongst women exposed to very high doses in the province
of Nova Scotia (P, heterogeneity <0.0001). Based on the combined data
sets a simple relative risk (RR) model for the effect of a dose of D
sieverts at age A years is developed: RR(D) = 1.0 + 0.52D exp[-0.10(A
- 15)]. This model fits the combined data well, and is used to predict
excess lifetime risks of breast cancer mortality after radiation expo
sure from routine annual mammography. (C) 1996 by Radiation Research S
ociety