Abstract：
BACKGROUND: The dose-response relationship between cancers and protracted low-dose rate exposure to ionising radiation is still uncertain. This study aims to estimate quantified relationships between low-dose radiation exposures and site-specific solid cancers among Chinese medical X-ray workers.
METHODS: This cohort study included 27 011 individuals who were employed at major hospitals in 24 provinces in China from 1950 to 1980 and had been exposed to X-ray equipment, and a control group of 25 782 physicians who were not exposed to X-ray equipment. Person-years of follow-up were calculated from the year of employment to the date of the first diagnosis of cancer or the end of follow-up, whichever occurred first. All cancers were obtained from medical records during 1950-1995. This study used Poisson regression models to estimate the excess relative risk (ERR) and excess absolute risk (EAR) for incidence of site-specific solid cancers associated with cumulative dose.
RESULTS: 1643 solid cancers were developed, the most common being lung, liver and stomach cancer. Among X-ray workers, the average cumulative colon dose was 0.084 Gy. We found a positive relationship between cumulative organ-specific dose and liver (ERR/Gy=1.48; 95% CI 0.40 to 2.83), oesophagus (ERR/Gy=18.1; 95% CI 6.25 to 39.1), thyroid (ERR/Gy=2.96; 95% CI 0.44 to 8.18) and non-melanoma skin cancers (ERR/Gy=7.96; 95% CI 2.13 to 23.12). We found no significant relationship between cumulative organ-specific doses and other cancers. Moreover, the results showed a statistically significant EAR for liver, stomach, breast cancer (female), thyroid and non-melanoma skin cancers.
CONCLUSIONS: These findings provided more useful insights into the risks of site-specific cancers from protracted low-dose rate exposure to ionising radiation.
METHODS: This cohort study included 27 011 individuals who were employed at major hospitals in 24 provinces in China from 1950 to 1980 and had been exposed to X-ray equipment, and a control group of 25 782 physicians who were not exposed to X-ray equipment. Person-years of follow-up were calculated from the year of employment to the date of the first diagnosis of cancer or the end of follow-up, whichever occurred first. All cancers were obtained from medical records during 1950-1995. This study used Poisson regression models to estimate the excess relative risk (ERR) and excess absolute risk (EAR) for incidence of site-specific solid cancers associated with cumulative dose.
RESULTS: 1643 solid cancers were developed, the most common being lung, liver and stomach cancer. Among X-ray workers, the average cumulative colon dose was 0.084 Gy. We found a positive relationship between cumulative organ-specific dose and liver (ERR/Gy=1.48; 95% CI 0.40 to 2.83), oesophagus (ERR/Gy=18.1; 95% CI 6.25 to 39.1), thyroid (ERR/Gy=2.96; 95% CI 0.44 to 8.18) and non-melanoma skin cancers (ERR/Gy=7.96; 95% CI 2.13 to 23.12). We found no significant relationship between cumulative organ-specific doses and other cancers. Moreover, the results showed a statistically significant EAR for liver, stomach, breast cancer (female), thyroid and non-melanoma skin cancers.
CONCLUSIONS: These findings provided more useful insights into the risks of site-specific cancers from protracted low-dose rate exposure to ionising radiation.
摘要：
背景：癌症与长期低剂量率暴露于电离辐射之间的剂量-反应关系仍不确定。这项研究旨在评估中国医学X射线工作者中低剂量辐射暴露与特定部位实体癌之间的量化关系。
方法：这项队列研究包括1950年至1980年在中国24个省的主要医院受雇并暴露于X射线设备的27011人，和一个由25782名没有暴露于X射线设备的医生组成的对照组。从就业年到首次诊断出癌症或随访结束之日，计算了随访的人年，以先发生者为准。所有癌症均来自1950-1995年的医疗记录。这项研究使用泊松回归模型来估计与累积剂量相关的位点特异性实体癌的发生率的超额相对风险（ERR）和超额绝对风险（EAR）。
结果：发现了1643种实体癌，最常见的是肺，肝癌和胃癌.在X光工作者中,平均累积结肠剂量为0.084Gy。我们发现累积器官特异性剂量与肝脏之间存在正相关关系（ERR/Gy=1.48;95％CI0.40至2.83），食管（ERR/Gy=18.1；95%CI6.25~39.1），甲状腺(ERR/Gy=2.96;95%CI0.44~8.18)和非黑色素瘤皮肤癌(ERR/Gy=7.96;95%CI2.13~23.12)。我们发现累积器官特异性剂量与其他癌症之间没有显着关系。此外，结果显示肝脏有统计学意义的EAR，胃,乳腺癌（女性），甲状腺和非黑色素瘤皮肤癌。
结论：这些发现为长期低剂量率暴露于电离辐射的特定部位癌症的风险提供了更有用的见解。
方法：这项队列研究包括1950年至1980年在中国24个省的主要医院受雇并暴露于X射线设备的27011人，和一个由25782名没有暴露于X射线设备的医生组成的对照组。从就业年到首次诊断出癌症或随访结束之日，计算了随访的人年，以先发生者为准。所有癌症均来自1950-1995年的医疗记录。这项研究使用泊松回归模型来估计与累积剂量相关的位点特异性实体癌的发生率的超额相对风险（ERR）和超额绝对风险（EAR）。
结果：发现了1643种实体癌，最常见的是肺，肝癌和胃癌.在X光工作者中,平均累积结肠剂量为0.084Gy。我们发现累积器官特异性剂量与肝脏之间存在正相关关系（ERR/Gy=1.48;95％CI0.40至2.83），食管（ERR/Gy=18.1；95%CI6.25~39.1），甲状腺(ERR/Gy=2.96;95%CI0.44~8.18)和非黑色素瘤皮肤癌(ERR/Gy=7.96;95%CI2.13~23.12)。我们发现累积器官特异性剂量与其他癌症之间没有显着关系。此外，结果显示肝脏有统计学意义的EAR，胃,乳腺癌（女性），甲状腺和非黑色素瘤皮肤癌。
结论：这些发现为长期低剂量率暴露于电离辐射的特定部位癌症的风险提供了更有用的见解。
