Abstract: Objective To identify the influencing factors for the response to postoperative ¹³¹I treatment and prognosis in patients with intermediate and high-risk differentiated thyroid cancer(DTC)by employing optimal scale regression analysis and joint diagnostic ROC model analysis, so as to provide a reference basis for the development of clinical treatment plans. Methods A retrospective analysis was conducted on the clinical data of 414 patients with intermediate and high-risk differentiated thyroid cancer(DTC)who had undergone postoperative ¹³¹I treatment. The patients were divided into an intermediate-risk group(n=275)and a high-risk group(n=139)based on the risk of recurrence. Chi-square tests were used to compare the categorical data between the intermediate-risk and high-risk groups; the Mann-Whitney test was employed to compare the numerical data between the two groups. The Medcalc software was used to plot ROC curves and compare the diagnostic efficacy of predictive factors among the groups. Results Patients in the intermediate-risk and high-risk groups showed statistically significant differences in age, T stage, M stage, number of treatments, cumulative dose, thyroid-stimulating hormone, anti-thyroglobulin antibodies, and thyroglobulin levels(P<0.01). The effective predictive factors for treatment response in the intermediate-risk group were gender, number of treatments, and cumulative dose, with the cumulative dose having the largest area under the curve(AUC), but it was still smaller than the AUC of the combined diagnostic model of all three factors. In both the intermediate and high-risk groups, the cumulative dose, T stage, and M stage were predictive factors, with the cumulative dose having the largest AUC, which was also smaller than the AUC of the combined diagnostic model of the three factors. The effective predictive factors for mortality risk in the intermediate and high-risk groups were T stage and M stage, with M stage having the largest AUC. The AUC for the combined diagnosis of T stage and M stage was slightly larger than that of M stage alone. Conclusion The most effective single factor for predicting the treatment response in intermediate and high-risk DTC patients is the cumulative dose, while the most effective single factor for predicting the risk of death is the M stage. The efficacy of the combined diagnostic model of all predictive factors is higher than that of any single factor, suggesting that aggressive ¹³¹I treatment is beneficial for improving the prognosis of intermediate and high-risk DTC patients.

Key words: Differentiated thyroid cancer, Intermediate- and high-risk patients, ¹³¹I treatment, Optimal scale regression analysis, Combined diagnosis