Locoregional progression-free survival of bone metastases from differentiated thyroid cancer.

To evaluate the locoregional progression-free survival (LPFS) of bone metastatic lesions from differentiated thyroid cancer (DTC) after radioiodine therapy (RAIT) and to define its influencing factors, we performed a retrospective cohort analysis of 89 patients with bone metastases from DTC who received RAIT in our department over a 17-year period. The median follow-up time was calculated using the reverse Kaplan-Meier method. The log-rank test and a multivariate Cox proportional hazards regression model were performed in the analysis of prognostic indicators for LPFS. In this research, the median follow-up time for all patients was 47 (95% CI, 35.752-58.248) months, and that for patients with no progression was 42 months. The longest follow-up time was 109 months. The median LPFS time was 58 (95% CI, 32.602-83.398) months, and the 3- and 5-year LPFS probabilities were 57.8 and 45.1%, respectively. Multivariate analysis revealed bone structural changes as an independent risk factor for LPFS (P= 0.004; hazard ratio, 49.216; 95% CI, 3.558-680.704). Furthermore, the non-total-lesion uptake subgroup presented a worse LPFS than the total-lesion uptake subgroup in patients with structural bone lesions (P = 0.027). RAIT can improve the LPFS of radioiodine-avid bone metastases from DTC, especially those without bone structural changes.