Long-Term Survival and Low Effective Cumulative Radioiodine Doses to Achieve Remission in Patients With 131Iodine-Avid Lung Metastasis From Differentiated Thyroid Cancer

Objective: To evaluate long-term survival and response to RAI treatment in patients with differentiated thyroid cancer (DTC) and (131)Iodine-avid metastatic lung disease. Patients and Methods: A retrospective review of 639 DTC patients followed-up at the Hospital de Clinicas, Buenos Aires, Argentina, showed that 42 (6%) patients had lung metastasis, and 24 patients were included for analysis. Results: Seventeen were women, and 7 were men (F: M = 2.4: 1). Eighteen patients (75%) had PTC, and 6 (25%) had FTC. The median age at diagnosis was older than 45 years in 50%, and the median follow-up was 13 years. Good response to treatment (GRT: no evidence of disease or biochemical persistence without structural correlate) was observed in 46% of patients (all with diffuse postdose radioiodine uptake and no structural images higher than 1 cm in diameter); and 21% patients died from disseminated lung metastasis. Overall survival at 5 and 10 years was 100% and 88.4%, respectively. The Cox proportional hazard ratio showed that extrathyroidal invasion, positive uptake of 18-FDG, and metachronous diagnosis of the lung metastasis were variables that significantly predicted death. Those patients who had a GRT did with a mean effective cumulative RAI dose of 457.3 +/- 29.7 mCi I-131 (range, 300-600 mCi 131I). Conclusions: Lung metastasis showed a slow progression with a high long-term overall survival. The presence of synchronous lung metastasis, the absence of nodules larger than 1 cm, and the lack of uptake of (18)FDG were predictive factors for an early response to treatment with RAI cumulative doses lower than 600 mCi I-131.