Sunitinib-induced thyrotoxicosis - a not so rare entity.

BACKGROUND/AIM The tyrosine kinase inhibitor (TKI) sunitinib malate is nowadays a standard first-line treatment option for patients with metastatic clear-cell renal cell carcinoma (mRCC). The aim of this study was to evaluate the incidence and clinical course of thyrotoxicosis in our cohort of patients treated with sunitinib. PATIENTS AND METHODS Medical records of all patients treated with first-line sunitinib for mRCC at our Institution between November 2008 and March 2014 were retrospectively reviewed. Thyroid function was assessed after every 2 cycles of therapy, during the 2 weeks off period. RESULTS Out of the 62 included patients, hypothyroidism has developed during therapy in 12 patients (19%) and it was preceded by thyrotoxicosis in 2 (3.2%). CONCLUSION Sunitinib-induced thyrotoxicosis (SIT), a not so rare entity, was followed by hypothyroidism. The patterns of occurrence and possible significance of SIT, as predictive marker of better treatment response to sunitinib, need to be validated in further studies.