The prognosis and treatment of primary thyroid cancer occurred in breast cancer patients: comparison with ordinary thyroid cancer

PURPOSE Due to the increased prevalence of thyroid cancer, it has been frequently detected in breast cancer patients recently. The aim of this study was to evaluate the clinicopathologic characteristics of thyroid cancer in breast cancer patients with respect to prognosis and treatment. METHODS From August 1998 to September 2012, 101 breast cancer patients were diagnosed with thyroid cancer (BT group). One hundred ninety-three female patients with a thyroid malignancy that underwent thyroidectomy in 2008 were recruited as controls (oT group). The clinicopathologic results of these two groups were compared. RESULTS Patients were older (51.40 vs. 47.16, P < 0.001), mean tumor size was smaller (0.96 cm vs. 1.43 cm, P < 0.001), and extrathyroidal extension was less common in the BT group. In both groups, papillary thyroid carcinoma was the most common type of thyroid malignancy. T and N classifications of thyroid cancer were less severe in the BT group, but group TNM stages were similar. Endoscopic thyroid surgery was performed in 12.9% of patients in the BT group and in 6.7% of patients in the oT group. Postoperative radioactive iodine ablation was performed less often in the BT group (P < 0.001). Group recurrence rates were not significantly different. CONCLUSION Thyroid cancer in breast cancer patients was diagnosed at earlier status than ordinary thyroid cancer. However, the prognosis of thyroid cancer in breast cancer patients was not superior to that in patients with thyroid cancer alone. Radioactive iodine ablation was performed less often and endoscopic surgery could be performed in breast cancer patients.