The impact of sunitinib-induced hypothyroidism on progression-free survival of metastatic renal cancer patients: a prospective single-center study.

BACKGROUND: Several studies have reported unexpected rates of hypothyroidism in patients treated with sunitinib. The biochemical basis of this impairment is unknown. A relationship between hypothyroidism and improved outcome has been suggested in some cancer patients. Here we describe the incidence of newly onset hypothyroidism and its relationship with progression-free survival in metastatic renal cell carcinoma patients undergoing sunitinib treatment at our institution. PATIENTS AND METHODS: Between July 2007 and June 2009, 22 patients received a first line sunitinib for metastatic renal cell carcinoma. Thyroid function tests were prospectively evaluated as routine laboratory assessment in every patient, at baseline and on the first and last day of every ON and OFF sunitinib period. RESULTS: The median duration of treatment was 39.5 weeks. During sunitinib therapy, 13 patients (59.1%) showed at least one elevated TSH level. No reductions of TSH below normal ranges were observed. L-thyroxine replacement therapy was required in 2 patients. Based on thyroid function, median progression-free survival was 8.55 months for hypothyroid compared with 7.03 months for euthyroid patients (P < 0.05). CONCLUSION: Patients administered sunitinib have an high incidence of hypothyroidism. The improved outcome of hypothyroid patients suggests an important relationship between sunitinib and this uncommon side effect.