Long-term Outcomes and Prognostic Factors in Patients with Differentiated Thyroid Cancer and Distant Metastases

ABSTRACT

Objective: Distant metastatic spread is the most frequent cause of thyroid cancer-related death. The objective of this study was to evaluate overall and disease-related survival of patients with differentiated thyroid cancer (DTC) and distant metastases (DM) attending a single medical center and to investigate variables predictive of better long-term outcomes. Methods: The Rabin Medical Center Thyroid Cancer Registry was searched for patients with DM from DTC. Results: The cohort included 138 patients (58.7% female) diagnosed at age 54.7±19.5 years. Mean primary tumor size was 33.9 ± 26 mm. Most patients (57.7%) were stage T3/T4; 48.7% had extrathyroidal extension; 53.5% had lymph node metastases. Histopathology yielded papillary and follicular thyroid carcinoma in 66.7% and 13.8%, respectively, and intermediate/poorly differentiated carcinoma in 19.6%. All but 2 patients underwent total thyroidectomy, and 133/138 (96.4%) received radioactive iodine (RAI) therapy. DM were synchronous in 55.1%. The mean follow-up was 8.2 years from detection of metastases. The common sites of metastases were the lungs (85.6% of patients), bones (39.9%), brain (5.8%) and liver (3.6%). At last follow-up, resolution was documented in 24.6% of patients, improvement/stable disease in 31.6%, and structurally progressive disease in 43.4%. By the end of the study, 40.6% of patients died, 23.2% of DTC. Improved overall survival and disease progression were associated with younger age, lung-only DM, and metastatic RAI avidity. Conclusion: Patients with DTC and DM treated by standard-of-care approaches frequently achieve favorable long-term outcomes. Novel therapies might be necessary in only a minority of these patients, and the reported prognostic factors can aid in their identification. Abbreviations: CR = complete response; DM = distant metastases; DTC = differentiated thyroid cancer; ETE = extra-thyroidal extension; M0 = detected during follow-up; M1 = detected at diagnosis; MSKCC = Memorial Sloan Kettering Cancer Center; NED = no evidence of disease; OS = overall survival; PFS = progression free survival; PTC = papillary thyroid cancer; RAI = radioactive iodine; Tg = thyroglobulin