title: Benign thyroid disease is associated with breast cancer: a meta-analysis.
abstract: The controversial relationship between benign thyroid diseases and breast cancer (BC) 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 BC 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 BC, further prospective studies are required to definitively prove causality.
authors.affiliation: The Whiteley-Martin Research Centre, Discipline of Surgery, Sydney Medical School Nepean, Nepean Hospital, The University of Sydney, Level 5, South Block, PO Box 63, Penrith, NSW 2751, Australia. phar5793@uni.sydney.edu.au
authors.forename: Prue J
authors.initials: PJ
authors.lastname: Hardefeldt
authors.forename: Guy D
authors.initials: GD
authors.lastname: Eslick
authors.forename: Senarath
authors.initials: S
authors.lastname: Edirimanne
mesh_terms: D001323:Autoantibodies / Q000276:immunology; D001327:Autoimmune Diseases / Q000150:complications / Q000276:immunology; D001943:Breast Neoplasms / Q000150:complications* / Q000453:epidemiology / Q000276:immunology; D005260:Female; D006042:Goiter / Q000150:complications / Q000276:immunology; D006111:Graves Disease / Q000150:complications; D006801:Humans; D006980:Hyperthyroidism / Q000150:complications; D007037:Hypothyroidism / Q000150:complications; D016017:Odds Ratio; D013959:Thyroid Diseases / Q000150:complications* / Q000276:immunology; D013967:Thyroiditis, Autoimmune / Q000150:complications / Q000276:immunology
chemical_list: D001323:Autoantibodies