Benign thyroid disease is associated with breast cancer: a meta-analysis.

Wednesday, 03/04/2013  |   Breast Cancer  |  no comments

Hardefeldt PJ, Eslick GD, Edirimanne S. Breast Cancer Res Treat. 2012 Jun;133(3):1169-77. doi: 10.1007/s10549-012-2019-3. Epub 2012 Mar 21.

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The controversial relationship between benign thyroid diseases and breast cancer (BCa) has been investigated for over 50 years. Despite extensive population studies, the results as a whole have been inconsistent. The purpose of this study was to collate and analyse available data, calculating a pooled odds ratio (OR) of the risk of BC in patients diagnosed with benign thyroid diseases.

Studies were obtained from a database search of MEDLINE, EMBASE, PubMed, Current Contents Connect and Google Scholar with additional cross checking of reference lists. Inclusion criteria required a confirmed diagnosis of a benign thyroid disease, reporting of an OR or data to calculate an OR (and 95% confidence interval, CI) and the use of an internal control group as the comparator. Collated data was assessed for heterogeneity and a pooled OR calculated. 28 studies were included in the meta-analysis. There was significant evidence of an increased risk of BCa in patients with autoimmune thyroiditis, evident in a pooled OR 2.92 (95% CI 2.13-4.01). In addition, the results supported an increased risk associated with the presence of anti-thyroid antibodies (OR 2.02, 95% CI 1.63-2.50) and goitre (OR 2.26, 95% CI 1.39-3.69). Subgroup analysis of antibody presence revealed increased risk associated with both anti-TPO (OR 2.64, 95% CI 1.82-3.83) and anti-TG (2.71, 95% CI 1.58-4.69).

Quantitative analysis of hypothyroidism and hyperthyroidism was not significant. While these results indicate an association between thyroid auto-immunity and BCa, further prospective studies are required to definitively prove causality.

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