Purpose: We conducted a phase II study to assess the efficacy of continuous dosing of sunitinib in patients with flurodeoxyglucose positron emission tomography (FDG-PET)-avid, iodine-refractory well-differentiated thyroid carcinoma (WDTC) and medullary thyroid cancer (MTC) and to assess for early response per FDG-PET.
Experimental design: Patients had metastatic, iodine-refractory WDTC or MTC with FDG-PET-avid disease. Sunitinib was administered at 37.5 mg daily on a continuous basis. The primary end point was response rate per Response Evaluation Criteria in Solid Tumors (RECIST). Secondary end points included toxicity, overall survival, and time to progression. We conducted an exploratory analysis of FDG-PET response after 7 days of treatment.
Results: Thirty-five patients were enrolled (7 MTC, 28 WDTC), and 33 patients were evaluable for disease response. The primary end point, objective response rate per RECIST, was 11 patients (31%; 95% confidence interval, 16-47%). There were 1 complete response (3%), 10 partial responses (28%), and 16 patients (46%) with stable disease. Progressive disease was seen in 6 patients (17%). The median time to progression was 12.8 months (95% confidence interval, 8.9 months-not reached). Repeat FDG-PET was done on 22 patients. The median percent change in average standardized uptake values was -11.7%, -13.9%, and 8.6% for patients with RECIST response, stable disease, and progressive disease, respectively. Differences between response categories were statistically significant (P = 0.03). The most common toxicities seen included fatigue (11%), neutropenia (34%), hand/foot syndrome (17%), diarrhea (17%), and leukopenia (31%). One patient on anticoagulation died of gastrointestinal bleeding.
Conclusion: Continuous administration of sunitinib was effective in patients with iodine-refractory WDTC and MTC. Further study is warranted.