Abstract:Objective To investigate the efficacy of apatinib combined with levothyroxine sodium and ¹³¹I in the treatment of differentiated thyroid carcinoma (DTC), and its impact on immune indicators and thyroid function parameters in DTC patients. Methods A total of 86 DTC patients diagnosed at Handan First Hospital from January 2020 to December 2023 were selected as the study subjects and randomly divided into a conventional group and an apatinib group, with 43 patients in each group. The conventional group was treated with levothyroxine sodium and ¹³¹I, while the apatinib group received apatinib in addition to the conventional treatment. Both groups were treated continuously for one month. The clinical efficacy, Karnofsky Performance Status (KPS) score, vascular endothelial growth factor (VEGF), cytokeratin 19 fragment antigen 21-1 (CYFRA21-1), thyroid-related indicators [thyroglobulin (TG), anti-thyroglobulin antibody (TGAb), anti-thyroid peroxidase antibody (TPOAb), thyroid-stimulating hormone (TSH), free triiodothyronine (FT3), free thyroxine (FT4)], immune function indicators, and the incidence of adverse reactions were observed in both groups after treatment. Results Two patients in the conventional group dropped out, resulting in 41 patients in the conventional group and 43 patients in the apatinib group included in the final analysis. After treatment, the total effective rate in the apatinib group was higher than that in the conventional group [95.35% (41/ 43) vs 78.05% (32/41), χ²=5.520, P=0.019]. The KPS scores of both groups increased after treatment, with the apatinib group showing a higher score than the conventional group (P<0.05). The levels of VEGF, CYFRA21-1, TPOAb, TG, TGAb, and TSH in both groups decreased after treatment compared to before treatment, and the apatinib group was significantly lower than the conventional group (P<0.05). The levels of FT3, FT4, CD3⁺, CD4⁺, and CD4⁺/ CD8⁺ in both groups increased after treatment compared to before treatment, and the apatinib group was significantly higher than the conventional group (P<0.05). There was no statistically significant difference in the total incidence of adverse reactions between the conventional group and the apatinib group [17.07% (7/41) vs 9.30% (4/43), χ²=1.114, P= 0.291]. Conclusion Apatinib combined with levothyroxine sodium and ¹³¹I in the treatment of DTC can effectively improve clinical efficacy, regulate thyroid hormone levels, promote the recovery of thyroid function, increase KPS scores, inhibit tumor angiogenesis, enhance immune function, and demonstrate high safety.