Background: Differentiated thyroid cancer (DTC) with distant metastases at presentation is uncommon; the prognosis of patients with this condition is more favorable than for other cancers. Demographic, clinical, and pathologic characteristics are described at a population level; factors associated with long-term disease-specific survival are identified.
Methods: Patients were identified in the Surveillance, Epidemiology, and End Results (SEER) database between 1988 and 2009. They were divided into two groups: patients with distant metastases (met-DTC) and patients without distant metastases (DTC) at presentation. Data analyses were performed with chi square tests, ANOVA, Kaplan-Meier analysis, and binary logistic and Cox proportional hazards regression.
Results: A total of 1,291 patients with met-DTC at diagnosis and 58,518 with DTC were included. The met-DTC rate was 2.2 %; compared to DTC, met-DTC patients were more often male (22.7 vs 41.3 %, respectively; p < 0.001) and older (mean 48.8 vs 62.7 years; p < 0.001). Patients with met-DTC were more likely not to have had surgery (23.3 vs 2.0 %; p < 0.001) or to have received radiation therapy (RAI) (66.8 vs 46.5 %; p < 0.001). Met-DTC tumors were larger (mean 41.0 vs 20.5 mm; p < 0.001). Independent factors associated with distant metastases were male gender, older age, single status, black and "other" races, follicular and Hurthle cell histology, larger tumors, and positive regional lymph nodes. Disease-specific survival was lower for met-DTC; this has not improved over the past two decades (p = 0.494). Independent factors associated with mortality included patient age ≥ 45 years, single status, follicular and Hurthle cell histologies, tumor size >4 cm, and not receiving surgery and/or RAI.
Conclusions: Overall, met-DTC is uncommon. Given the lack of survival improvement observed over the last two decades, novel treatments should be pursued aggressively for this subset of patients.