CORONADO, CALIF. (FRONTLINE MEDICAL NEWS)In patients with radioactive iodine–refractory differentiated thyroid cancer, those with target lesions less than 1.5 cm in size appeared to derive less benefit from sorafenib in terms of progression-free survival, results from an international study showed.

In addition, papillary histology was a positive predictive factor and a predictive factor for benefit from sorafenib.

“Patients with radioactive iodine–refractory differentiated thyroid cancer have a poor prognosis, and there is a lack of effective treatments,” Dr. Martin Schlumberger said at the annual meeting of the American Thyroid Association. “The median survival for this subset is estimated to be 2.5-5 years.”

Sorafenib was approved by the Food and Drug Administration in November 2013 for the treatment of radioactive iodine–refractory differentiated thyroid cancer based on results from the randomized, controlled, double-blind phase III DECISION trial (Lancet 2014;384:319-28 ). Investigators found that the use of sorafenib extended median progression-free survival by 5 months, compared with placebo (10.8 vs 5.8 months; P < .0001). The purpose of the current analysis was to determine which demographic baseline or disease-related characteristics are prognostic for better outcomes in this patient population. To do so, Dr. Schlumberger of the department of nuclear medicine and endocrine oncology at Gustave Roussy, Villejuif, France, and his associates performed multivariate Cox proportional hazards models adjusted for treatment effect.

He reported findings from 417 patients. Of these, 210 were randomized to receive placebo and 207 were randomized to receive sorafenib. Variables found to be prognostic factors for progression-free survival in placebo patients, and in all patients when adjusted for sorafenib treatment, included papillary histology, lower targeted tumor size, baseline thyroglobulin less than 486 ng/mL, lower number of lesions, and residing in Asia vs. Europe and North America. Subgroup analyses of patients in the sorafenib arm revealed that the following baseline or disease-related variables were predictive of progression-free survival: papillary histology, tumor size of at least 1.5 cm, and having only lung metastases.

In a post-hoc exploratory analysis of progression-free survival by thyroid cancer symptoms among all 417 patients at study entry, the researchers found that both symptomatic and asymptomatic patients had improved progression-free survival following treatment with sorafenib.

On the basis of these findings, radioactive iodine–refractory differentiated thyroid cancer patients with no progressive disease and a tumor size of less than 1.5 cm “appear to have a good prognosis and may be candidates for a ‘watch and wait’ approach before initiating treatment with sorafenib,” Dr. Schlumberger concluded.

Dr. Schlumberger is an adviser to AstraZeneca, Bayer, Eisai, Exelixis, and Genzyme. He has also received research support from Genzyme and Bayer.

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