Major Finding: Overall, 28 of 789 women with goiter also had breast cancer, for a prevalence of 3.6%.
Data Source: A review of 789 women with nontoxic goiter.
Disclosures: Dr. Sanghvi reported having no financial conflicts to disclose.
SAN DIEGO – Women with nontoxic goiter were more than twice as likely to have breast cancer compared with women in the general population, according to a review of data from 789 women with nontoxic, multinodular goiter, uninodular goiter, or simple goiter.
Data from previous studies of a potential link between thyroid disorders and breast cancer are inconclusive, said Sarika Patel Sanghvi, D.O., of Robert Wood Johnson Medical School in New Brunswick, N.J.
In this study, Dr. Sanghvi and her colleagues compared breast cancer incidence in women with nontoxic goiter with breast cancer incidence in the general population of New Jersey. Breast cancer history was obtained from each patient's medical history.
Overall, 28 of 789 women with goiter also had breast cancer, for a prevalence of 3.6%. By contrast, the prevalence of breast cancer in the general population, based on data from the New Jersey Department of Health and Senior Services, was significantly lower at 1.6%.
Two of the 28 patients with breast cancer had low TSH levels, but one had a free T4 within normal limits and the other had a total T4 within normal limits, said Dr. Sanghvi. Four of the 28 patients had serum thyroid peroxidase (TPO) antibodies, only one level of which was elevated, but this patient had normal TSH and free T4 levels, Dr. Sanghvi said.
The association between breast cancer and nontoxic goiter is unclear, she said. Possible mechanisms include the role of iodine, thyroid-stimulating hormone, and estrogen.
“Iodine has been theorized as being a causative factor, because it is utilized by both breast and thyroid tissues,” and these are the only two organs in which iodine is stored. Dr. Sanghvi explained. However, epidemiologic studies are needed to explore the association between iodine and breast cancer.
The results were limited by the retrospective nature of the study, and the lack of a standard medical history questionnaire. But they underscore the important of breast cancer screening in women with benign thyroid disease until larger, prospective studies provide additional information, Dr. Sanghvi said.
In the study population as a whole, the average age was 51 years, the average body mass index was 29.2 kg/m
One of the patients with breast cancer had ductal carcinoma in situ; the breast cancer types in the other 27 patients were not specified.