According to data for patients in the Phase I/II trial of sunitinib (Sutent), 36% developed hypothyroidism during treatment with sunitinib, and the incidence of hypothyroidism increased with duration of treatment. These findings were published in November 2006 by Desai et al in the Annals of Internal Medicine (click for abstract).

Desai et al report that “15 of 42 patients (36%) developed hypothyroidism after an average of 50 weeks of therapy (range 12 to 94 weeks)” and an additional 7 patients (17%) had an abnormal serum thyroid stimulating hormone (TSH) test result at at least one point during treatment. Two patients’ thyroid glands atrophied, becoming undetectable on imaging. All patients responded to treatment with L-thyroxine.

Hypothyroidism has also been reported in a separate study of renal cell carcinoma patients treated with sunitinib (AJ Martorella et al, abstract 593 presented at 88th annual meeting of the Endocrine Society, Boston, June 2006) and in a study published in January 2007 by Rini et al entitled “Hypothyroidism in patients with metastatic renal cell carcinoma treated with sunitinib.”

Desai et al recommended that patients on sunitinib therapy be “screened for the development of hypothyroidism with frequent measurements of TSH, perhaps at 2- to 3-month intervals.” They recommended L-thyroxine treatment if indicated, as well as consultation with an endocrinologist. The authors stated that “hypothyroidism is easily treated and is not in itself an indication for the discontinuation of sunitinib therapy given its effectiveness in treating life-threatening conditions.”