Study validates an association between thyroid and breast cancer

A single center retrospective case-controlled study performed by Jee Hyun An and colleagues of Seoul National University College of Medicine, South Korea and published in December 2015 issue of Thyroid.

The study group consists of 4243 patients with differentiated Thyroid Carcinoma (TC) and 6833 patients with Breast Cancer (BC) while the control group consisted of age matched patients without second malignancies.

In the study group with TC , 55 patients subsequently developed BC in the 5 year follow up, while among  those patients with BC  81 patients developed subsequent TC during a 6.2-year follow-up.

The expression of estrogen and progesterone receptors was significantly higher in the tissues of BC patients with coexisting TC compared with those with BC alone suggesting  a molecular association between both the cancers.

A slight increase in incidence of BC in TC patients may be due to increased screening procedure due to a primary malignancy.

Clinically, the findings suggest that regular breast examination and screening guidelines to be followed in patients with TC.

However, because there were no clinical predictors of TC development among the BC patients compared with those with TC alone and no evidence of improved prognosis for early TC diagnosis, "screening for TC in BC patients cannot be recommended, irrespective of the patient's age at BC diagnosis."

Many earlier studies have demonstrated an increase prevalence of thyroid disease like nontoxic goiter, Hashimoto's thyroiditis, Graves' disease, thyroid carcinoma, and subacute thyroiditis in patients treated for Breast Cancer as compared to age matched controls.

Clinically this means that women with primary breast cancer, screening for thyroid disease particularly hypothyroidism and autoimmune thyroiditis should be carried out for extended period of time even after the patient is cure of the primary cancer.

References:
http://www.ncbi.nlm.nih.gov/pubmed/8772562
http://online.liebertpub.com/doi/abs/10.1089/thy.2014.0561
http://www.ncbi.nlm.nih.gov/pubmed/1465285