Clinical outcomes and implication of radioactive iodine therapy on cancer-specific survival in WHO classification of FTC.

BACKGROUND:The clinical outcomes and implications of radioactive iodine therapy (RAIT) on cancer-specific survival (CSS) in World Health Organization (WHO) classification of follicular thyroid carcinoma (FTC) are not well established. MATERIAL AND METHODS:The data of eligible patients with minimally invasive FTC (mi-FTC), encapsulated angioinvasive FTC (ea-FTC), or widely invasive FTC (wi-FTC) between 2000 and 2020 were extracted from the Surveillance, Epidemiology, and End Results (SEER) database. Cancer-specific survival (CSS), the primary outcome, was compared among the three subtypes of FTC patients before and after adjusting for differences using propensity score matching (PSM). The FTC patients in different subtypes were then divided into two groups: the RAIT group and the no-RAIT group. Cox proportional hazards regression analyses were applied to discover the relationships of factors associated with CSS in the each PSM cohort. RESULTS:A total of 2433 mi-FTC patients, 216 ea-FTC patients, and 554 wi-FTC patients were enrolled in the original cohorts, respectively. Patients with mi-FTC or ea-FTC had similar CSS (p =0.805), which was better than that of patients with wi-FTC (p <.001; p =0.021). Cox proportional hazards regression analysis revealed that RAIT was not associated with improved CSS in either the mi-FTC PSM cohort (HR =1.21, 95% CI=0.46-3.18, p =0.705) or the wi-FTC PSM cohort (HR =0.56, 95% CI=0.35-1.08, p =0.086). However, subgroup analysis demonstrated that wi-FTC patients with N1 stage (HR =0.44, 95% CI=0.20-0.99, p =0.018) or M1 stage (HR =0.25, 95% CI=00.11-0.53, p <.001) could gain CSS advantage from RAIT. CONCLUSIONS:The RAIT can provide a CSS advantage for wi-FTC patients who with N1-stage or M1-stage disease.