Time Course and Predictors of Structural Disease Progression in Pulmonary Metastases Arising from Follicular Cell-Derived Thyroid Cancer.

BACKGROUND With the advent of molecular targeted therapy for the management of radioactive iodine (RAI) refractory, progressive metastatic thyroid cancer, it becomes important to define the time course and risk factors for structural disease progression in follicular cell-derived thyroid cancer (FCDTC) patients. This will help in defining the optimal time to start these therapies and better define their impact on structural disease progression. OBJECTIVES This retrospective review of 199 consecutive patients with FCDTC presenting with lung metastasis examined the progression-free survival (PFS) in thyroid cancer patients with lung metastasis treated with surgery and RAI, and who had not received molecular targeted therapy or chemotherapy. RESULTS The median overall survival (OS) was 10.45 years, while the median PFS was 3.65 years. A strong correlation was found between OS and PFS. PFS is shorter in patients with RAI refractory disease, poorly differentiated/Hürthle cell histologies, male sex, fluorodeoxyglucose-avid metastatic foci, older age (>45 years), and pulmonary metastases >1 cm. At final follow-up (a median of 6.9 years from lung metastasis diagnosis), 68% of the patients had progressed and 46% had died. CONCLUSIONS With the exception of younger patients with low disease burden, most patients presenting with lung metastasis from FCDTC (RAI avid and RAI refractory) using standard-of-care approaches will have disease progression on long-term follow-up. Additional studies are needed to identify novel therapies that would improve the PFS of such patients.