In patients with advanced thyroid cancer, sunitinib, a drug approved for treatment of several other cancers, showed significant cancer-fighting activity t, a new phase 2 clinical trial has found. Results of the single-center study will be presented Sunday at the Endocrine Society's 97th annual meeting in San Diego.

"Sunitinib can potentially be used as an effective adjunctive treatment in patients with advanced differentiated thyroid cancer," said Principal Investigator Kenneth Burman, MD, Chief of Endocrine at MedStar Washington Hospital Center, Washington, D.C.

Differentiated thyroid cancer is the most common type of cancer of the thyroid, a gland in the neck. For patients with this type of cancer, surgery and treatment with radioactive iodine to destroy the cancer cells are very effective, but in some patients, the tumor will continue to progress.

Burman and his colleagues tested the treatment effect of sunitinib in 23 patients with advanced-stage differentiated thyroid cancer who had undergone at least one course of radioactive iodine treatment. Primarily, they measured progression-free survival, the length of time that the tumor did not progress. They also measured the response of tumor growth to sunitinib using the Response Evaluation Criteria in Solid Tumors (RECIST). Patients received a starting daily dose (37.5 milligrams) of oral Sunitinib

The median progression-free survival was 241 days, or about eight months, the researchers reported.

Because this was a Phase 2 clinical trial, there was no control group. The investigators compared their results against that of the control group from a recently published study in patients with the same type of cancer who received a placebo, or "dummy" pill. Compared with these controls, Burman and his group found that the progression-free survival (PFS) with Sunitinib treatment in their study was significantly longer than without it. Further, the PFS using Sunitinib was comparable to that previously reported for Sorafenib.

According to the study abstract, 83 percent of sunitinib-treated patients benefited from treatment, with either significant shrinkage of the tumors (partial response) or slowed disease progression (stable disease). Six patients (26 percent) had a partial response to Sunitinib, and 13 (57 percent) had stable disease.

"Sunitinib is not a cure but it appears from this study that it may slow the progression of disease," Burman said.

He added that, in general, their patients tolerated the medicine fairly well, with the most commonly reported adverse events being mild or moderate.

Sunitinib is currently available for the treatment of advanced renal cell cancer and two other types of cancer under the brand name Sutent, from Pfizer, which supported this study. A targeted therapy, sunitinib works by inhibiting multiple proteins in cancer cells, limiting cancer cell growth and division.

According to Burman, sunitinib merits a larger, controlled, phase 3 trial for treatment of advanced differentiated thyroid cancer.