BREAST-CANCER AMONG RADIOLOGIC TECHNOLOGISTS

Objective.-To evaluate the risk of breast cancer among women occupatio nally exposed to ionizing radiation. Design.-Case-control study. Parti cipants.-A health survey of 105 385 women radiologic technologists cer tified by the American Registry of Radiologic Technologists since 1926 . Among 79016 respondents, 600 breast cancer cases were identified. Ea ch of 528 eligible subjects with breast cancer was matched to five con trol subjects based on age, year of certification, and follow-up time. Main Outcome Measures.-Relative risk (RR) estimated as the relative o dds ratio for breast cancer over categories of years worked as a radio logic technologist and according to personal and occupational exposure characteristics. Results.-Study subjects had been certified for a mea n of 29 years; 63.8% of cases and 62.6% of controls worked as radiolog ic technologists for 10 years or more. Significant increased risks for breast cancer were associated with early age at menarche (for <11 yea rs of age: RR=1.79; 95% confidence interval [CI], 1.09 to 2.94), nulli parity (RR=1.36; 95% CI, 1.04 to 1.78), first-degree relative with his tory of breast cancer(RR=2.07; 95% CI, 1.56 to 2.74), prior breast bio psy (RR=1.53; 95% CI, 1.17 to 2.00), alcohol consumption (for >14 alco holic drinks per week: RR=2.12; 95% CI, 1.06 to 4.27), thyroid cancer (RR=5.36; 95% CI, 1.64 to 17.5), hyperthyroidism (RR=1.66; 95% CI, 1.0 2 to 2.71), and residence in the northeastern United States (RR=1.66; 95% CI, 1.19 to 2.30). Jobs involving radiotherapy, radioisotopes, or fluoroscopic equipment, however, were not linked to breast cancer risk , nor were personal exposures to fluoroscopy or multifilm procedures. Use of birth control pills, postmenopausal estrogens, or permanent hai r dyes also were not risk factors. Based on dosimetry records for 35% of study subjects, cumulative exposures appeared low. Among women who worked more than 20 years, the RR for breast cancer was 1.13 (95% CI, 0.79 to 1.64). Conclusions.-More than 50% of the reported breast cance rs could be explained by established risk factors. Employment as a rad iologic technologist, however, was not found to increase the risk of b reast cancer. The contribution of prolonged exposure to relatively low doses of ionizing radiation to breast cancer risk was too small to be detectable at this time.