Abnormalities of thyroid function in Japanese patients with metastatic renal cell carcinoma treated with sorafenib: A prospective evaluation

The objective of this study was to characterize features of thyroid dysfunction in Japanese patients with metastatic renal cell carcinoma (RCC) who were treated with sorafenib. We performed a prospective observational study including 69 Japanese patients who were diagnosed as having metastatic RCC refractory to cytokine therapy and subsequently treated with sorafenib for at least 12 weeks. Thyroid function was assessed before and every 4 weeks after the initiation of sorafenib treatment. Of the 69 patients, 23 (33.3%) did not show any biochemical thyroid abnormality, while the remaining 46 (67.7%) developed hypothyroidism. However, 11 (23.9%) of these 46 hypothyroid patients initially had a suppressed thyroid-stimulating hormone (TSH) value accompanying the increase in free triiodothyronine (T3) and/or free thyroxine (T4) before developing hypothyroidism, suggesting sorafenib-induced thyroiditis. During the observation period of this study, 4 patients (5.8%) demonstrated severe clinical symptoms caused by hypothyroidism and received thyroid hormone replacement. Among several factors examined, only age was significantly associated with the risk for hypothyroidism. These findings suggest that although the incidence of clinically significant hypothyroidism requiring thyroid hormone replacement therapy was not very high, biochemical thyroid abnormality was frequently observed in Japanese RCC patients treated with sorafenib. Accordingly, regular surveillance of thyroid function by the measurement of TSH, free T3, and T4 is warranted during sorafenib treatment in Japanese RCC patients.