Watch Thyroid While on Sutent (ZT)

Half of Users Develop Thyroid Problems, Study Finds

November 22, 2006 11:58:55 AM PST

Yahoo! Health: Cancer News

Summary: Patients who take the targeted drug Sutent (sunitinib) should have their thyroid function routinely monitored, according to doctors from Harvard Medical School, Brigham and Women's Hospital, and the Dana-Farber Cancer Institute. More than half of people taking the drug developed some kind of thyroid problem during treatment, the researchers report in a new study.

Why it's important: Sutent is approved to treat people with advanced kidney cancer and people with gastrointestinal stromal tumor (GIST) who cannot take Gleevec (imatinib) or whose tumor no longer responds to Gleevec. In both cases, patients have few other treatment options available to them. Because Sutent is a relatively new drug, doctors are still learning about its side effects. Because the thyroid problems linked to Sutent are treatable, patients taking the drug end up having a better quality of life.

What's already known: During early clinical trials of Sutent for GIST, 2 patients developed an underactive thyroid, a condition called hypothyroidism. Hypothyroid glands produce too little thyroid hormone. Symptoms include fatigue, sensitivity to cold, constipation, hoarseness, and dry skin. Because fatigue was a commonly reported symptom among trial participants, the researchers decided to investigate whether Sutent might be causing thyroid problems.

How this study was done: The researchers measured levels of thyroid hormone in the blood of patients with GIST who were about to start treatment with Sutent as part of a clinical trial of the drug. They continued measuring thyroid levels as long as patients were taking the medication. They published their findings in the Annals of Internal Medicine.

What was found: Of the 79 patients in the trial, 42 had normal thyroid function before beginning Sutent therapy and were included in the analysis. After an average of about 9 months of treatment with Sutent, 15 of the 42 (36%) had developed underactive thyroid, and 26 people (62%) had some kind of thyroid abnormality. The longer patients took Sutent, the more likely they were to develop underactive thyroid.

People who had underactive thyroid were given levothyroxine, the standard treatment for this condition, and their thyroid levels normalized.

The bottom line: The researchers suggest people who are being treated with Sutent should be checked every 2-3 months for thyroid problems. Those with abnormal results should be evaluated more thoroughly, and those found to have underactive thyroid should be treated with levothyroxine.

More studies are needed to figure out how Sutent is affecting thyroid function, the researchers say. However, because underactive thyroid is easily treated, this side effect should not cause people to quit successful Sutent therapy, they add.

Citation: "Hypothyroidism After Sunitinib Treatment for Patients Wth Gastrointestinal Stromal Tumors." Published in the Nov. 7, 2006, Annals of Internal Medicine (Vol. 145, No. 9: 660-664). First author: Jayesh Desai, MD,