Pazopanib Holds Promise in Advanced Thyroid Cancers

Pazopanib represents a therapeutic option for patients with advanced differentiated thyroid cancers. A phase II trial conducted at the Mayo Clinic in Rochester, Minn., included 39 patients with metastatic, rapidly progressive, radioiodine-refractory differentiated thyroid cancers.

Each patient received 800 mg of continuous pazopanib daily in four-week cycles until disease progression, drug intolerance, or both were reached. The primary endpoint was tumor response.

Partial responses were recorded in 18 patients (response rate 49%) with the likelihood of a response lasting longer than one year calculated to be 66%.

According to the results, maximum concentration of pazopanib in plasma during the first cycle was significantly correlated with radiographic response. Of the 39 patients, 16 (43%) required dose reductions owing to adverse events, including fatigue, skin and hair hypopigmentation, diarrhea, and nausea. Two patients who died during treatment had pre-existing contributory disorders, according to the study authors (Lancet Oncol 11:962-972, 2010).

"The correlation of the patient’s response and pazopanib concentration during the first cycle might indicate that treatment can be individualised to achieve optimum outcomes," wrote lead investigator Keith Bible, MD, and colleagues.

"Assessment of pazopanib in an expanded cohort of patients with differentiated thyroid cancer, as well as in cohorts of patients with medullary and anaplastic thyroid cancers, is presently being done." The study results offered a better idea as to the potential therapeutic role of tyrosine kinase inhibitors in thyroid cancer, they said GSK and Provenge GlaxoSmithKline will supply the antigen used to manufacture prostate cancer vaccine Provenge, according to a regulatory filing by Dendreon.

Dendreon placed its first order for about $8.3 million worth of antigen. The contract is set to run through the end of 2015.