There is a clear association between co-occurrence of breast cancer and differentiated thyroid cancer, and clinicians should consider the increased risk for second primary cancers when treating this patient population, according to a meta-analysis.1

University of Chicago researchers performed a systematic review and meta-analysis of the literature using PubMed and Scopus search engines to find publications that studied the incidence of breast cancer as a secondary malignancy following a thyroid cancer diagnosis, and vice versa.

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Results showed that women with a breast cancer diagnosis had an increased risk of thyroid cancer as a secondary malignancy (odds ratio = 1.55; 95% CI, 1.44 – 1.67), and those diagnosed with thyroid cancer had an increased risk of developing breast cancer as a secondary malignancy (odds ratio = 1.18; 95% CI, 1.09 – 1.26).

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Possible explanations for the association include surveillance bias, hormonal risk factors, radiation exposure, genetic susceptibility, and obesity.

The researchers determined that the importance of this association will become more evident as incidences of both cancers rise and treatments continue to improve, allowing patients with cancer to live longer and develop secondary malignancies.


  1. Nielsen SM, White MG, Hong S, et al. The breast-thyroid cancer link: a systematic review and meta-analysis. Cancer Epidemiol Biomarkers Prev. 2016;25(2):231-238.