Miller A B, Howe G R, Sherman G J, Lindsay J P, Yaffe M J, Dinner P J, Risch H A, Preston D L
National Cancer Institute of Canada Epidemiology Unit, Toronto.
N Engl J Med. 1989 Nov 9;321(19):1285-9. doi: 10.1056/NEJM198911093211902.
The increasing use of mammography to screen asymptomatic women makes it important to know the risk of breast cancer associated with exposure to low levels of ionizing radiation. We examined the mortality from breast cancer in a cohort of 31,710 women who had been treated for tuberculosis at Canadian sanatoriums between 1930 and 1952. A substantial proportion (26.4 percent) had received radiation doses to the breast of 10 cGy or more from repeated fluoroscopic examinations during therapeutic pneumothoraxes. Women exposed to greater than or equal to 10 cGy of radiation had a relative risk of death from breast cancer of 1.36, as compared with those exposed to less than 10 cGy (95 percent confidence interval, 1.11 to 1.67; P = 0.001). The data were most consistent with a linear dose-response relation. The risk was greatest among women who had been exposed to radiation when they were between 10 and 14 years of age; they had a relative risk of 4.5 per gray, and an additive risk of 6.1 per 10(4) person-years per gray. With increasing age at first exposure, there was substantially less excess risk, and the radiation effect appeared to peak approximately 25 to 34 years after the first exposure. Our additive model for lifetime risk predicts that exposure to 1 cGy at the age of 40 increases the number of deaths from breast cancer by 42 per million women. We conclude that the risk of breast cancer associated with radiation decreases sharply with increasing age at exposure and that even a small benefit to women of screening mammography would outweigh any possible risk of radiation-induced breast cancer.
越来越多地使用乳房X线摄影术来筛查无症状女性，因此了解与低水平电离辐射暴露相关的乳腺癌风险变得很重要。我们研究了1930年至1952年间在加拿大疗养院接受过结核病治疗的31710名女性队列中的乳腺癌死亡率。相当一部分（26.4%）女性在治疗气胸期间因多次荧光透视检查而接受了10 cGy或更高剂量的乳房辐射。与接受辐射剂量低于10 cGy的女性相比，接受辐射剂量大于或等于10 cGy的女性患乳腺癌死亡的相对风险为1.36（95%置信区间1.11至1.67；P = 0.001）。数据最符合线性剂量反应关系。在10至14岁时接受辐射的女性中风险最高；她们每格雷的相对风险为4.5，每格雷每104人年的附加风险为6.1。随着首次暴露年龄增加，额外风险大幅降低，辐射效应似乎在首次暴露后约25至34年达到峰值。我们的终生风险附加模型预测，40岁时暴露于1 cGy会使每百万女性中因乳腺癌死亡的人数增加42人。我们得出结论，与辐射相关的乳腺癌风险随着暴露年龄的增加而急剧下降，即使乳房X线摄影筛查对女性有微小益处，也会超过辐射诱发乳腺癌的任何可能风险。
