Background

Second primary neoplasms are associated with high mortality and morbidity rates in cancer survivors successfully treated for the first malignancy. Studies suggested an association between the type of first neoplasm and risk of subsequent thyroid cancer, with part of this risk attributable to exposure to radiotherapy during treatment of the first primary tumor. This study aimed to determine whether radiotherapy is a risk factor for thyroid cancer in patients previously treated for another neoplasm.

Methods

This retrospective case-control study included patients diagnosed with their first cancer between 2007 and 2017. Patients who subsequently developed thyroid cancer as a second primary neoplasm were defined as “cases”, and patients who did not develop a second cancer were defined as “controls”. Exposure to radiotherapy was the primary risk factor of interest; other risk factors were the site to which radiotherapy was delivered and the first neoplasm type.

Results

Exposure to radiotherapy was associated with an increased risk of thyroid cancer (odds ratio [OR] = 2.410, 95% confidence interval [CI]: 1.219–4.764), in particular, in women (OR = 3.121, 95% CI: 1.232–7.907) and in patients receiving radiotherapy to the thorax (OR = 6.298, 95% CI: 2.581–15.370). The median survival time from first cancer recovery to thyroid cancer occurrence was 63.80 months; there was no difference in survival between patients who did and did not receive radiotherapy (P = 0.899).

Conclusion

Radiation to the thorax can increase the risk of thyroid cancer as a second neoplasm among patients with cancer successfully treated for their first cancer.

中文翻译：

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第一原发癌放疗暴露作为第二原发甲状腺癌的危险因素：病例对照研究

背景

在成功治疗第一种恶性肿瘤的癌症幸存者中，第二原发肿瘤与高死亡率和发病率相关。研究表明，首发肿瘤的类型与随后发生甲状腺癌的风险之间存在关联，这种风险的部分原因是在治疗第一个原发肿瘤期间接受了放射治疗。本研究旨在确定放射治疗是否是先前接受过其他肿瘤治疗的患者发生甲状腺癌的危险因素。

方法

这项回顾性病例对照研究包括在 2007 年至 2017 年间被诊断出患有第一次癌症的患者。随后将甲状腺癌作为第二原发肿瘤的患者定义为“病例”，未发生第二次癌症的患者定义为“对照组” ”。放疗暴露是主要的风险因素；其他风险因素是放疗的部位和第一种肿瘤类型。

结果

放疗暴露与甲状腺癌风险增加相关（优势比 [OR] = 2.410，95% 置信区间 [CI]：1.219–4.764），尤其是在女性中（OR = 3.121，95% CI：1.232– 7.907) 和接受胸部放疗的患者 (OR = 6.298, 95% CI: 2.581–15.370)。从第一次癌症康复到甲状腺癌发生的中位生存时间为 63.80 个月；接受和未接受放疗的患者的生存率没有差异（P  = 0.899）。

结论

在成功治疗第一次癌症的癌症患者中，对胸部进行辐射会增加甲状腺癌作为第二次肿瘤的风险。