Patterns of radioiodine uptake combined with pulmonary nodule size in predicting long-term clinical outcomes of differentiated thyroid carcinoma patients with lung metastasis alone.

Objectives: This study aimed to evaluate the role of radioiodine uptake patterns and pulmonary nodule size in predicting progression- free survival (PFS) and overall survival (OS) in DTC patients with lung metastases only. Methods: A retrospective study was conducted on 189 DTC patients with pulmonary metastasis alone who were treated and monitored at the Department of Nuclear Medicine, Hospital 108, Vietnam from January 2004 to December 2018. They were categorized based on radioiodine uptake patterns on post-therapy whole-body scans (WBS) and CT-based pulmonary nodule sizes. Prognostic factors were identified by Kaplan-Meier survival and Cox regression. Results: The 5-year and 10-year OS rates were 96.83 % and 94.71 %. DTC-LM patients with diffuse radioiodine uptake and miliary metastases demonstrated significantly higher survival rates, with 5-year and 10-year PFS rates of 100% and 98.8%, respectively. In contrast, patients with nonavid metastases exhibited a markedly lower prognosis, with 5-year and 10-year PFS rates of 58.8% and 25.2%, respectively (p<0.001). Patients with nodules <5 mm had 5-year and 10-year PFS rates of 88.8% and 73.8%, respectively, while those with nodules 5-10 mm had rates of 79.8% and 52.7%. Patients with nodules ≥10 mm experienced the worst outcomes, with 5-year and 10-year PFS rates of 70.6% and 29.3% (p<0.001). Multivariate analysis confirmed that non-avid metastases, nodule size ≥10 mm, and age ≥55 were independent predictors of poor prognosis (HR:24.99, 5.96, and 6.58; p<0.001). Conclusions: Patterns of radioiodine uptake and pulmonary nodule sizes on CT imaging are crucial predictors of long-term clinical outcomes in DTC-LM. Diffuse iodine uptake and military pulmonary metastases are associated with favorable outcomes, while non-avid lung nodules and larger nodule sizes predict poorer survival.