Endocrine Abstracts

Introduction: The bidirectional relationship of risk between breast cancer (BC) and thyroid cancer (TC) has been debated. Estrogens are proposed as agents implicated in the risk of developing TC promoting thyroid tumorigenesis. Therapies that reduce the effect of estrogens on their receptors in cancer cells are widely used.

Objective: To correlate the use of hormonal therapy in BC with the prevalence of TC.

Material and Methods: We performed a retrospective analysis of female patients with nodular thyroid pathology and BC followed in our consultation from January 2016 to January 2021. The variables were analyzed using the SPSS software; they are expressed as mean and standard deviation (with a 95% confidence interval).

Results: A total of 3253 patients with nodular thyroid disease were identified. In 4.1% of patients (n=132) BC was described in the medical records. Twenty-eight patients were excluded due to lack of data. Regarding the patients included (n=104), the mean age at diagnosis of BC was 56±12 years. Patients underwent radiotherapy in 75.9% of cases (n=79), hormonal therapy in 72.1% (n=75) and chemotherapy in 52.9% (n=55). Considering the largest thyroid nodule, the mean diameter in thyroid ultrasound was 22.8±8.5 mm. Fine needle aspiration cytology (FNAC) was performed in 88.5% of patients (n=92) and was repeated in 23.9% (n=22), mostly due to an initial non-diagnostic result. Considering both procedures, the result was benign in 82.6% (n=76), non-diagnostic in 9.8% (n=9), follicular lesion of undetermined significance in 2.2% (n=2), suspected of malignancy in 2.2% (n=2), Hürthle cell tumor in 1.1% (n=1) and follicular tumor in 2.2% (n=2). Thyroid surgery was performed in 18.3% of patients (n=19) with a prevalence of thyroid malignancy of 8.7% (n=9). Papillary thyroid carcinoma was diagnosed in eight patients and follicular thyroid carcinoma in one patient. Compared with patients who did not undergo hormonal therapy, patients undergoing hormonal therapy did not show a decrease in cytological (OR=0.88 [0.16-4.88];P=0.88)) or histological (OR=0.28 [0.07-1.15];P=0.08)) risk of TC.

Conclusion: An increased risk of thyroid cancer has been reported in breast cancer survivors. Despite the published evidence on the role of estrogens in the association of BC and TC, in our studied sample there was no relationship between the use of hormonal therapy and the prevalence of TC. Further studies with a larger sample size should be encouraged.