Prognostic value of adjuvant external beam radiotherapy for papillary thyroid cancer based on competitive risk model and propensity score matching

Background: This study aimed to assess the impact of adjuvant external beam radiotherapy (EBRT) on the survival of patients with locally invasive papillary thyroid carcinoma. Methods: This retrospective study used data from the Surveillance, Epidemiology, and End Results database for the diagnosis of papillary thyroid carcinoma, using Cox models to screen for adverse prognostic factors. The prognostic value of using adjuvant external beam radiotherapy in papillary thyroid carcinoma was further evaluated, based on the competing risk model and propensity score matching. Results: : Based on the competitive risk model, the sub-distribution hazard ratio (SHR) of the multivariate analysis of patients receiving EBRT alone versus those receiving radioiodine-131 alone was 9.301 (95% CI, 5.99–14.44) (P<0.001), and the SHR of the univariate analysis was 1.97 (95% CI, 1.03–3.78) (P=0.042). In the propensity score-matched Kaplan–Meier analysis, patients who received EBRT still had worse OS (6-year OS, 59.62% vs 74.6%; P<0.001) and DSS (6-year DSS, 66.6% vs. 78.2%; P<0.001) than patients who did not receive EBRT. Patients who received EBRT had a higher cumulative risk of death due to thyroid cancer after PSM (P<0.001). Conclusion: Adjuvant EBRT was not associated with survival benefit in the initial management of locally invasive papillary thyroid cancer.