The Impact of Distant Metastases at Presentation on Prognosis in Patients with Differentiated Carcinoma of the Thyroid Gland

Abstract

Distant metastases at presentation are rare in well-differentiated thyroid cancer (WDTC). The objective of this study was to report outcomes for patients presenting with distant metastases managed by thyroidectomy and radioactive iodine (RAI) therapy. Fifty-two patients with distant metastases from thyroid cancer diagnosed before thyroid surgery (n=32) or on a postoperative RAI scan after thyroid surgery (n=20) were identified from a database of patients with WDTC treated between 1985 and 2005. The median age was 58 years (range 12-83 years), with a male-to-female ratio of 3:2. Forty-seven patients (90%) had total thyroidectomy and two (4%) had thyroid lobectomy, and three patients (6%) were found to be unresectable. Distant metastases were classified into pulmonary and extrapulmonary. Overall survival (OS), disease-specific survival (DSS), and locoregional recurrence-free survival were calculated by the Kaplan-Meier method. Factors predictive of the outcome were determined by univariate and multivariate analyses. Thirty-nine patients (75%) were diagnosed with pulmonary metastases alone and 13 (25%) with extrapulmonary metastases. The sites of extrapulmonary metastases were bone in nine, mediastinum in one, pyriform sinus in one and skin in one, and one patient had synchronous lung, bone, and intracerebral metastases. After thyroid surgery, 47 patients (90%) were treated with RAI alone, and 2 patients had external beam radiation in addition to RAI. With a median follow-up after surgery of 78.5 months, the 5-year OS and DSS were 65% and 68%, respectively. Twenty-nine patients (56%) died during follow-up, of whom 24 (46%) died of thyroid cancer. Six patients (12%) developed recurrent disease in the lateral neck, and three patients (6%) developed recurrence in the thyroid bed. Over 45 years, follicular pathology and extrapulmonary metastases were predictive of lower 5-year DSS (56% vs. 100%, p<0.001; 50% vs. 70%, p=0.004; and 46% vs. 75%, p=0.013, respectively). Approximately half of patients with WDTC presenting with distant metastases die of disease within 5 years of initial diagnosis despite thyroid surgery and RAI. Age over 45 years, extrapulmonary metastases, and follicular pathology were significant predictors of the poor outcome.