Breast cancer risk and protracted low-to-moderate dose occupational radiation exposure in the US Radiologic Technologists Cohort, 1983-2008.
BACKGROUND
Although high-dose ionising radiation is associated with increased breast cancer risks, the association with protracted low-dose-rate exposures remains unclear. The US Radiologic Technologist study provides an opportunity to examine the association between low-to-moderate dose radiation and breast cancer incidence and mortality.


METHODS
One thousand nine hundred and twenty-two self-reported first primary cancers were diagnosed during 1983-2005 among 66 915 female technologists, and 586 breast cancer deaths occurred during 1983-2008 among 83 538 female cohort members. Occupational breast dose estimates were based on work histories, historical data, and, after the mid-1970s, individual film badge measurements. Excess relative risks were estimated using Poisson regression with birth cohort stratification and adjustment for menopause, reproductive history, and other risk factors.


RESULTS
Higher doses were associated with increased breast cancer incidence, with an excess relative risk at 100 mGy of 0.07 (95% confidence interval (CI): -0.005 to 0.19). Associations were strongest for technologists born before 1930 (excess relative risk at 100 mGy=0.16; 95% CI: 0.03-0.39) with similar patterns for mortality among technologists born before 1930.


CONCLUSIONS
Occupational radiation to the breast was positively associated with breast cancer risk. The risk was more pronounced for women born before 1930 who began working before 1950 when mean annual doses (37 mGy) were considerably higher than in later years (1.3 mGy). However, because of the uncertainties and possible systematic errors in the occupational dose estimates before 1960, these findings should be treated with caution.
Hirosoft International, 1335 H, Eureka, CA 95501, USA.
D L
DL
Preston
Radiation Epidemiology Branch, Division of Cancer Epidemiology and Genetics, National Cancer Institute, 9609 Medical Center Drive, Rockville, MD 20850, USA.
C M
CM
Kitahara
Radiation Epidemiology Branch, Division of Cancer Epidemiology and Genetics, National Cancer Institute, 9609 Medical Center Drive, Rockville, MD 20850, USA.
D M
DM
Freedman
Radiation Epidemiology Branch, Division of Cancer Epidemiology and Genetics, National Cancer Institute, 9609 Medical Center Drive, Rockville, MD 20850, USA.
A J
AJ
Sigurdson
Radiation Epidemiology Branch, Division of Cancer Epidemiology and Genetics, National Cancer Institute, 9609 Medical Center Drive, Rockville, MD 20850, USA.
S L
SL
Simon
Radiation Epidemiology Branch, Division of Cancer Epidemiology and Genetics, National Cancer Institute, 9609 Medical Center Drive, Rockville, MD 20850, USA.
M P
MP
Little
Radiation Epidemiology Branch, Division of Cancer Epidemiology and Genetics, National Cancer Institute, 9609 Medical Center Drive, Rockville, MD 20850, USA.
E K
EK
Cahoon
Radiation Epidemiology Branch, Division of Cancer Epidemiology and Genetics, National Cancer Institute, 9609 Medical Center Drive, Rockville, MD 20850, USA.
P
P
Rajaraman
Information Management Services Inc., 6110 Executive Boulevard No. 310, Rockville, MD 20852, USA.
J S
JS
Miller
Division of Environmental Health Sciences, School of Public Health, University of Minnesota, 426 Church Street SE, Minneapolis, MN 55455, USA.
B H
BH
Alexander
Radiation Epidemiology Branch, Division of Cancer Epidemiology and Genetics, National Cancer Institute, 9609 Medical Center Drive, Rockville, MD 20850, USA.
M M
MM
Doody
Radiation Epidemiology Branch, Division of Cancer Epidemiology and Genetics, National Cancer Institute, 9609 Medical Center Drive, Rockville, MD 20850, USA.
M S
MS
Linet
D000368:Aged; D000369:Aged, 80 and over; D001943:Breast Neoplasms / Q000453:epidemiology* / Q000209:etiology; D005260:Female; D006801:Humans; D015994:Incidence; D017056:Medical Laboratory Personnel / Q000706:statistics & numerical data; D009381:Neoplasms, Radiation-Induced / Q000453:epidemiology* / Q000209:etiology; D016273:Occupational Exposure / Q000706:statistics & numerical data*; D011829:Radiation Dosage; D018787:Radiation Oncology; D011839:Radiation, Ionizing; D000072177:Radiologists / Q000706:statistics & numerical data; D012307:Risk Factors; D014481:United States / Q000453:epidemiology; D000078329:Workforce