Prognostic disparities between radioactive iodine-refractory and non-refractory DTC patients: a cohort study on survival rates and independent risk factors.

AIMS: Patients with distant metastases of differentiated thyroid cancer (DM-DTC) exhibit significant heterogeneity in clinical characteristics and prognosis. This study aimed to investigate prognostic variables affecting overall survival (OS) in radioiodine-refractory (RAIR) patients and to predict the radioiodine therapy (RAIT) response and stimulated thyroglobulin (sTg) levels in non-radioiodine-refractory (NRAIR) patients. METHODS: A retrospective analysis was conducted on 146 patients of DM-DTC undergoing RAIT, categorizing them into an RAIR group (n = 56) and an NRAIR group (n = 90). Kaplan-Meier assessed survival, Cox regression identified RAIR prognostic factors, and logistic regression explored sTg-treatment response in NRAIR. RESULTS: The median follow-up period was 71 months (IQR: 24-132 months).In RAIR, brain metastasis (HR = 5.49, 95% CI: 1.46-20.66, p = 0.012) and other-site metastases (HR = 4.11, 95% CI: 1.06-15.85, p = 0.004) were independent poor prognostic factors. In NRAIR, sTg ≤ 75 ng/mL predicted favorable response (sensitivity 84.8%, specificity 78.9%). CONCLUSIONS: RAIR status significantly impacts DM-DTC prognosis. Brain metastases or other-site metastases are independent prognostic factors in RAIR patients, highlighting the need for stratified treatment. In NRAIR patients, preliminary data suggest that sTg ≤ 75 ng/mL predicts a favorable treatment response.