Clinical factors associated with prognosis in patients with differentiated thyroid cancer with lung metastases treated with radioiodine therapy

Purpose This retrospective study aimed to identify clinical factors associated with prognosis and to develop a scoring system to predict treatment efficacy in patients with differentiated thyroid cancer (DTC) who developed lung metastases following radioiodine therapy (RAI). Methods Among 300 patients who received RAI at our institution between January 1, 2017, and December 31, 2022, 74 exhibited lung metastases. We constructed a scoring system based on age (< 55 years vs. ≥55 years), the size of lung metastases (< 10 mm vs. ≥10 mm), the total diameter of lung metastases (≤ 20 mm vs. >20 mm), the presence or absence of iodine-131 ( ¹³¹ I) uptake, and the pretreatment serum thyroglobulin (Tg) level (< 100 vs. ≥100 ng/mL). Each factor was assigned a specific point value, yielding a total possible score ranging from 0 to 7. Results The median progression-free survival (PFS) for all patients was 46.3 months, and the median overall survival (OS) was 76.0 months. Among these patients, 20 had ¹³¹ I -avid lung metastases. In univariate analyses, age, size of lung metastases, total diameter of lung metastases, pretreatment Tg level, and ¹³¹ I uptake were significantly associated with PFS. In multivariate analyses, the size of lung metastases and the presence or absence of ¹³¹ I uptake were identified as independent prognostic factors. Based on the scoring system, patients were categorized into low-risk (0–2 points), intermediate-risk (3–4 points), and high-risk (5–7 points) groups. Both PFS and OS were significantly shorter in the high-risk group. Conclusion The scoring system developed in this study may serve as a valuable tool to guide treatment decisions based on risk stratification.