Could thyroid dysfunction influence outcome in sunitinib-treated metastatic renal cell carcinoma?

Background: Sunitinib is a standard of care for metastatic renal cell carcinoma (mRCC). Hypothyroidism is frequently observed under sunitinib therapy. This study was conducted to prospectively determine the correlation between thyroid function and progression-free survival (PFS) in this population. Patients and methods: One hundred and eleven mRCC patients treated with sunitinib were evaluated for serum thyroid-stimulating hormone (TSH) and T4 levels before treatment and every 6 weeks during treatment. Survival was analysed according to a landmark method with a cut-off of 6 months, excluding early progressive or early-censored patients. Results: Out of the 102 patients with normal baseline thyroid function, 53% developed thyroid dysfunction, including 95% hypothyroidisms out of which 90.9% received L-thyroxine replacement. Median time to TSH alteration was 5.4 months. Median PFS was 11.7 months for the entire population. Median PFS was not different between the groups with abnormal or normal thyroid function after 6 months of treatment (18.9 and 15.9 months, respectively, log-rank P = 0.94, hazard ratio = 1.02, 95% confidence interval = 0.54-1.93). There was no difference even after adjustment for Memorial Sloan-Kettering Cancer Centre classification and therapy line. Conclusions: Abnormal thyroid function with hormonal substitution did not increase survival in our population, independent of initial prognosis and previous treatments. Larger comparative studies are deserved to validate these conclusions.