Breast cancer mortality may be tied to prolonged exposure to low dose radiation

Women who worked as radiation technologists before 1950 have a higher risk of dying from breast cancer than those who began working in more recent years, report Aparna K. Mohan, M.D., Ph.D., now with the U.S. Food and Drug Administration, and her coworkers in the June 19 issue of the Journal of the National Cancer Institute.

Women exposed to high-dose radiation are known to be at increased risk of developing breast cancer. However, it is unclear how prolonged exposure to low or moderate levels of radiation influences breast cancer risk.

A previous study of female medical radiation workers in China suggested that breast cancer risk increased the further back these women were first employed. In the United States, women represent a large proportion of all medical radiation workers.

To examine breast cancer mortality among female medical radiation workers in the United States, Mohan and colleagues looked at radiation-exposure trends among 69,525 female radiologic technologists who completed an earlier questionnaire about their lifetime work histories, reproductive and family cancer histories, and other lifestyle factors that influence breast cancer risk. The women were certified as radiation technologists between 1926 through 1982. The average length of follow-up after the questionnaire was 12 years.

After adjusting for age of menopause, age at first birth, and family history of breast cancer, the authors found that women who began working as radiologic technologists before 1940 were nearly 3 times more likely to die from breast cancer than those first employed in 1960 or later. They also found that women who began working between 1940 and 1949 were about 2 1/2 times more likely to die of breast cancer compared with those who started working in 1960 or later.

Moreover, technologists who first performed fluoroscopy (an X-ray technique) and multifilm procedures before 1950 had statistically significantly higher risks compared with technologists who first performed these procedures in 1960 or later.

The authors note that the decline in risk over time probably reflects necessary reductions in the recommended radiation exposure limit.

Contact: Kathleen Kolar, U.S. Food and Drug Administration, (301) 827-6242; fax: (301) 827-1683, kkolar@oc.fda.gov

Mohan A, Hauptmann M, Linet M, Ron E, Lubin J, Freedman M, et al. Breast cancer mortality among female radiologic technologists in the United States. J Natl Cancer Inst 2002;94:943–8.

Attribution to the Journal of the National Cancer Institute is requested in all news coverage.

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