Radiotherapy for childhood cancer and subsequent thyroid cancer risk: a systematic review
Most of the pooled analyses and reviews reported an association between radiotherapy for childhood cancer and an increased thyroid cancer risk. Up to now this article presents the first systematic literature review on this association combined with a critical assessment of the methodological quality of the included articles. PubMed and Web of Science databases were searched for relevant articles until May 2016. We included peer-reviewed cohort and case–control studies that investigated an association between radiotherapy for childhood cancer and the occurrence of subsequent thyroid cancer. A systematic overview is presented for the included studies. We identified 17 retrospective cohort studies, and four nested case–control studies, representing 100,818 subjects. The age range at first cancer diagnosis was 0–25.2 years. Considerable variability was found regarding study sizes, study design, treatment strategies, dose information, and follow-up periods. 20 of the 21 identified studies showed increased thyroid cancer risks associated with childhood radiation exposure. The large majority showed an increased relative risk or odds ratio confirming the association between radiotherapy and thyroid cancer although the variation in results was large. Additionally to a pooled analysis that has been published recently, we systematically included 17 further studies, which allowed us to cover information from countries that were not covered by large-scale childhood cancer survivor studies. The methodological limitations of existing studies and inconsistencies in findings across studies yielded a large study heterogeneity, which made a detailed comparison of study results difficult. There is a need to strengthen standardisation for reporting.
KeywordsChildhood cancer survivors Haemangioma Radiation therapy Secondary thyroid cancer Systematic review
The authors would like to thank the Deutsche Krebshilfe (German Cancer Aid) for supporting this work (Award Number: 70111916). The content of this publication is solely the responsibility of the authors.
MB, PSK and RP wrote the grant application and laid down the overall principles of the study, and advised on conceptual issues. EL compiled the search. EL, PSK, and DB screened titles, abstracts and full-text articles for inclusion, and completed the quality and risk of bias assessment. EL led the review process, the analysis and the writing. All authors read, edited and approved the final manuscript.
Compliance with ethical standards
Conflict of interest
The authors declare that they have no conflict of interest.
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