Inskip P D, Ekbom A, Galanti M R, Grimelius L, Boice J D
Radiation Epidemiology Branch, National Cancer Institute, Bethesda, MD, USA.
J Natl Cancer Inst. 1995 Nov 1;87(21):1613-21. doi: 10.1093/jnci/87.21.1613.
Diagnostic x rays are the largest man-made source of exposure to ionizing radiation for the general population. Whether there are meaningful cancer risks associated with such exposures is unclear. Most previous case-control studies have relied on recalled histories of x rays, and there is concern that completeness and accuracy of recall might differ between cancer case and control subjects.
The present study used information recorded prospectively in hospital charts to address the relationship between medical diagnostic x rays and risk of thyroid cancer.
The Swedish Cancer Registry and the Uppsala-Orebro Regional Cancer Registry were used to identify persons with papillary or follicular thyroid cancer diagnosed from January 1, 1980, through December 31, 1992, among residents of the Uppsala Health Care Region. After histopathologic review, there were 484 such case subjects available for study. An equal number of age-, sex-, and county of residence-matched control subjects from the general population were randomly selected on the basis of the Swedish Registry of the Total Population. Lifetime residential histories were compiled, and radiology records were searched at all Swedish hospital serving regions where study subjects ever maintained an official residence. Approximate radiation doses to the thyroid gland for specific types of x-ray examinations were assigned on the basis of mean values of measurements made in Sweden in 1973-1975 and in the United States in 1970. Odds ratios were used to evaluate the association between diagnostic radiography and risk of thyroid cancer.
A total of 3853 medical diagnostic x rays were ascertained among thyroid cancer case subjects and 4039 among the matched control subjects. There were no tendency for case subjects to have had more of the types of x-ray procedure associated with higher radiation dose to the thyroid gland (i.e., those involving the head or neck area). This finding was true even when analysis was restricted to x rays occurring before 1960, when doses likely were higher than in more recent years, and for examinations occurring in childhood and adolescence, when susceptibility to radiation-induced thyroid cancer is greatest. The relative risk of thyroid cancer was not significantly associated with estimated cumulative dose to the thyroid gland from diagnostic x rays (two-sided P for trend = .80).
These data indicate that the risk of thyroid cancer due to medical diagnostic x rays, if any, is very small.
诊断性X射线是普通人群最大的人工电离辐射源。此类照射是否存在有意义的癌症风险尚不清楚。以往大多数病例对照研究依赖于对X射线照射史的回忆，人们担心癌症病例组和对照组在回忆的完整性和准确性上可能存在差异。
本研究利用医院病历中前瞻性记录的信息来探讨医学诊断性X射线与甲状腺癌风险之间的关系。
利用瑞典癌症登记处和厄勒布鲁地区癌症登记处，在厄勒布鲁医疗保健地区的居民中确定1980年1月1日至1992年12月31日期间诊断为乳头状或滤泡状甲状腺癌的患者。经过组织病理学复查后，有484例此类病例可供研究。根据瑞典总人口登记处，从普通人群中随机选择数量相等的年龄、性别和居住县匹配的对照对象。编制终生居住史，并在研究对象曾有正式居住的所有瑞典医院服务地区查找放射学记录。根据1973 - 1975年在瑞典以及1970年在美国进行的测量平均值，确定特定类型X射线检查对甲状腺的近似辐射剂量。采用比值比来评估诊断性放射摄影与甲状腺癌风险之间的关联。
在甲状腺癌病例组中总共确定有3853次医学诊断性X射线检查，在匹配的对照组中有4039次。病例组并没有接受更多与甲状腺较高辐射剂量相关的X射线检查类型（即涉及头部或颈部区域的检查）的倾向。即使将分析限于1960年以前进行的X射线检查（当时的剂量可能高于近年来）以及儿童期和青春期进行的检查（此时对辐射诱发甲状腺癌的易感性最大），这一发现仍然成立。甲状腺癌的相对风险与诊断性X射线对甲状腺的估计累积剂量无显著关联（趋势的双侧P值 = 0.80）。
这些数据表明，医学诊断性X射线所致的甲状腺癌风险（如果有的话）非常小。
