Predictive factors for therapeutic response to radioactive iodine therapy in pulmonary metastases from differentiated thyroid carcinoma.

PURPOSE: To evaluate the therapeutic outcomes of radioactive iodine (RAI) therapy for pulmonary metastases from differentiated thyroid carcinoma (DTC) and identify clinical factors predictive of treatment response.

METHODS

This retrospective study included 186 patients with pulmonary metastases of DTC who underwent RAI at our institution between 2010 and 2024. The treatment response was assessed based on integrated radiological and biochemical criteria using CT, I-131 scintigraphy, and serum thyroglobulin levels. Patients were classified as disease control complete response (CR), partial response (PR), stable disease (SD), or progressive disease (PD). Clinical variables including age, sex, histological subtype, timing of pulmonary metastasis diagnosis, maximum lesion diameter, pulmonary RAI uptake score, initial administered activity, and history of adjuvant RAI therapy were evaluated. Univariate and multivariate logistic regression analyses were performed to identify independent predictors of treatment response.

RESULTS

The overall disease control rate (CR + PR + SD) was 23.1%. Younger age (< 55 years) and synchronous detection of pulmonary metastases at the time of thyroid surgery were identified as independent predictors of a favorable treatment response (odds ratio = 3.77 and 2.65, respectively). A strong positive correlation was observed between the pulmonary RAI uptake score and the therapeutic outcome (Spearman's ρ = 0.683, p < 0.001). In contrast, the initially administered activity (100 vs. ≥ 150 mCi) was not significantly associated with treatment efficacy.

CONCLUSION

Younger age and synchronous detection of pulmonary metastases were identified as independent predictors, whereas pulmonary RAI uptake was strongly correlated with favorable RAI responsiveness in patients with DTC. The identified predictors of disease control may assist in optimizing patient selection and counseling for RAI therapy.