Single status shows age dependent bidirectional effects in differentiated thyroid cancer

Abstract

Abstract Thyroid cancer is one of the most common endocrine malignancies worldwide, and its prognosis is shaped by both tumor characteristics and social factors such as marital status. This study examined the association between single marital status and disease-specific survival (DSS) in differentiated thyroid cancer (DTC), with particular attention to its interaction with age. We analyzed 153,299 DTC cases diagnosed between 2000 and 2021 from the SEER database. Compared to married patients, single individuals were younger and exhibited larger tumors and more advanced N and M stages, though with more favorable overall TNM stages. Unadjusted Cox regression suggested a protective effect of single status (HR 0.79, 95% CI 0.72–0.87), which reversed after multivariable adjustment (HR 1.32, 95% CI 1.19–1.46). This pattern was consistent in papillary and follicular subtypes but not in Hürthle cell carcinoma. Age modified this effect: single status was protective in patients < 55 years (HR 0.89, 95% CI 0.81–0.99) but detrimental in those ≥ 55 years (HR 1.12, 95% CI 1.01–1.29). Significant interactions were observed on both multiplicative and additive scales. Fine–Gray competing risk models confirmed these findings. Overall, single status exerts an age-dependent influence on DTC prognosis and warrants consideration in risk assessment.