Inskip P D, Stovall M, Flannery J T
Radiation Epidemiology Branch, Division of Cancer Etiology, National Cancer Institute, Bethesda, Md.
J Natl Cancer Inst. 1994 Jul 6;86(13):983-8. doi: 10.1093/jnci/86.13.983.
Evidence shows ionizing radiation can cause lung cancer, but few studies have quantified risk in relation to radiation dose.
This study evaluated the long-term risk of lung cancer among women treated with radiation for breast cancer.
In this case-referent study, the Connecticut Tumor Registry was used to identify women diagnosed with histologically confirmed invasive breast cancer between 1935 and 1971 who survived for at least 10 years (8976) and to ascertain lung cancers occurring in this group between 1945 and 1981. Seventy-six cases of lung cancer were identified; however, 15 cases did not meet the criteria for inclusion. For the 61 remaining lung cancer case patients and 120 reference subjects (selected from the same registry and matched according to race, age at breast cancer diagnosis, year of breast cancer diagnosis, and survival without a second primary tumor), hospital charts were reviewed to collect medical history and radiotherapy information. A medical physicist estimated radiation dose to different segments of the lungs on the basis of radiotherapy reports and experimental simulations of treatments.
For these 10-year survivors of breast cancer, the overall relative risk (RR) of lung cancer associated with initial radiotherapy for breast cancer was 1.8 (95% confidence interval [CI] = 0.8-3.8), and the RR increased with time following treatment. The RR for periods of 15 years or more after radiotherapy was 2.8 (95% CI = 1.0-8.2). Mean dose was 15.2 Gy to the ipsilateral lung, 4.6 Gy to the contralateral lung, and 9.8 Gy for both lungs combined. The excess RR was 0.08 per Gy, based on average dose to both lungs, and 0.20 per Gy to the affected (cancerous) lung.
Breast cancer radiotherapy regimens in use before the 1970s were associated with an elevated lung cancer risk many years following treatment. The estimated risk coefficients are lower than those reported for atomic bomb survivors. The lower than expected risk might be attributable to high-dose cell killing or the fractionated nature of the exposure.
Approximately nine cases of radiotherapy-induced lung cancer per year would be expected to occur among 10,000 women who received an average lung dose of 10 Gy and survived for at least 10 years. Current radiotherapy for breast cancer results in less extensive exposure of the lungs in comparison to treatments of years past, and the risk of secondary lung cancer need not play a major role in clinical decisions regarding treatment for breast cancer. Nonetheless, efforts to reduce unnecessary exposure of the lungs and heart should continue to further reduce possible adverse radiation effects.
有证据表明电离辐射可导致肺癌，但很少有研究对辐射剂量相关的风险进行量化。
本研究评估了接受乳腺癌放疗的女性患肺癌的长期风险。
在这项病例对照研究中，康涅狄格肿瘤登记处用于识别1935年至1971年间被诊断为组织学确诊的浸润性乳腺癌且存活至少10年的女性（8976名），并确定该组在1945年至1981年间发生的肺癌。共识别出76例肺癌病例；然而，15例不符合纳入标准。对于其余61例肺癌病例患者和120名对照对象（从同一登记处选取，并根据种族、乳腺癌诊断时的年龄、乳腺癌诊断年份以及无第二原发性肿瘤存活情况进行匹配），查阅医院病历以收集病史和放疗信息。医学物理学家根据放疗报告和治疗的实验模拟估算肺部不同区域的辐射剂量。
对于这些乳腺癌10年幸存者，与乳腺癌初始放疗相关的肺癌总体相对风险（RR）为1.8（95%置信区间[CI]=0.8 - 3.8），且RR随治疗后的时间增加。放疗后15年或更长时间的RR为2.8（95%CI = 1.0 - 8.2）。患侧肺的平均剂量为15.2 Gy，对侧肺为4.6 Gy，双侧肺联合平均剂量为9.8 Gy。基于双侧肺的平均剂量，每Gy的超额RR为0.08，患侧（癌侧）肺每Gy为0.20。
20世纪70年代以前使用的乳腺癌放疗方案与治疗多年后肺癌风险升高相关。估计的风险系数低于原子弹幸存者报告的系数。风险低于预期可能归因于高剂量细胞杀伤或照射的分次性质。
在平均肺部剂量为10 Gy且存活至少10年以上的1万名女性中，预计每年约有9例放疗诱发的肺癌。与过去的治疗相比，当前乳腺癌放疗导致肺部的照射范围较小，继发性肺癌风险在乳腺癌治疗的临床决策中不必起主要作用。尽管如此，应继续努力减少肺部和心脏的不必要照射，以进一步降低可能的不良辐射效应。
