Endocrine Abstracts

Introduction: The standard treatment for differentiated thyroid carcinoma (DTC) with distant metastasis comprises complete total thyroidectomy and lymph node dissection, followed by radioactive iodine (RAI) ablation for metastatic lesions. However, between 2014 and 2015, sorafenib and lenvatinib have been approved for treatment of RAI-refractory advanced thyroid cancer in Japan. We retrospectively analyzed how the treatment results have changed after the approval of tyrosine kinase inhibitor (TKI) treatment.

Patients and methods: Among patients currently followed at outpatient clinics, 111 diagnosed with stage IV-C DTC who underwent surgery at our hospitals were included. A total of 48 patients with disease progression and an estimated lesion size ≥15 mm were treated with sorafenib and/or lenvatinib. The approval rate was 43.2%. Lesion evaluation was performed to compare and study these prognoses among 21 patients with lung metastasis, 18 with unresectable local recurrence, and nine with bone metastasis.

Results: Treatment results were classified as partial response (PR), stable disease (SD), not evaluable, and progressive disease (PD) in 16 (33.3%), 18 (37.5%), five (10.4%), and nine (18.8%) patients, respectively. The disease control rate (PR + SD) was 34/48 (70.8%) patients. Lesion evaluation showed that the disease control rate for pulmonary metastasis was the best (81.0%) and for bone metastasis (66.7%) and unresectable local recurrence (61.1%) was the worst (Table 1).

Conclusion: Because disease progression of pulmonary metastasis can be identified on a computed tomography image, the timing of TKI treatment was easy to determine and the treatment outcome was satisfactory. However, in some cases, local recurrence involved large blood vessels, or therapy was interrupted due to tumor-skin fistula or bleeding. Eventually, some patients died due to an adverse event (AE) or PD. Some cases of bone metastasis were initially diagnosed with large metastatic lesions, and the treatment outcomes were considered worse. Our results suggested that an appropriate timing of TKI administration and the control of its AEs can improve the prognosis of patients with stage IV-C DTCs with PD.