Axitinib treatment in advanced RAI-resistant differentiated thyroid cancer (DTC) and refractory medullary thyroid cancer (MTC).

6027 Background: Multikinase inhibitors (MKI) have demonstrated significant activity in advanced thyroid cancer. Axitinib is a potent oral MKI targeting the three known receptors of VEGF. Methods: Patients (pts) with advanced RAI-refractory DTC or unresectable MTC in documented disease progression were included in a compassionate use program of axitinib 5 mg bid. Primary end point was response rate (RR) by RECIST, and secondary objectives included progression-free survival (PFS), toxicity profile and biomarker correlation analysis. The program was validated by regulatory authorities and all patients signed informed consent form. Results: 41 pts were enrolled (med age: 54; male: 51%; 29 DTC, 12 MTC). Axitinib was first-line MKI therapy in 39%, second-line in 36% and 24% in subsequent lines. One level dose reduction (5 mg qd) was required in 24% of pts to manage toxicity. Main side effects were grade 1-2, including fatigue (46%), mucositis (24%), diarrhea (24%) and hypertension (19%). Grade 3-4 side effects...