Risk Factors, Prognostic Indicators, and a Prognostic Nomogram for Distant Metastasis in Thyroid Cancer Patients without Lymph Node Metastasis

Abstract

Abstract Background: Despite negative lymph node (N0) status, thyroid cancer (TC) patients may still experience distant metastasis (DM), which significantly affects their survival. This study aimed to investigate the risk factors for DM in thyroid cancer patients (N0) and develop a predictive nomogram model for analyzing the prognosis of TC N0 patients with DM. Methods: Collected data from the Surveillance, Epidemiology, and End Results (SEER) database for 18,487 thyroid cancer patients (N0) between 2004 and 2015 were analyzed. Multivariate logistic and Cox regression models were used to identify independent risk factors for DM and assess 1-, 3-, and 5-year overall survival (OS). Kaplan-Meier (K-M) survival curve was used to analyze the survival probability and cumulative risk of patients with different variables in the subgroup of DM in TC N0, and the Cox analysis results were used to construct an innovative nomogram model. The nomogram model's performance was evaluated using receiver operating characteristic (ROC) curves, concordance index (C-index), and calibration curves. Result: Six variables, including age (P < 0.001), race (P = 0.002), grade (P < 0.001), histology (P < 0.001), T stage (P < 0.001), and median income (P = 0.030), were identified as independent predictors of DM in thyroid cancer patients (N0), and we further achieved a good AUC of 0.837 (95% CI: 0.812–0.862) when predicting the risk of DM in TC N0. Similarly, age at diagnosis (p<0.001), sex (p<0.001), grade (p<0.001), histology (p<0.001), T stage (p<0.001), tumor size (p<0.001), and surgery (p<0.001) were identified as independent prognostic factors of DM in thyroid cancer patients (N0). An OS predictive nomogram was developed based on these factors, which demonstrated good performance according to the ROC, C-index, and calibration curves. In the training cohort, the areas under the ROC for 1-, 3-, and 5-year OS were 0.941, 0.915, and 0.902, respectively, while in the validation cohort, they were 0.929, 0.913, and 0.899. Conclusion: This study examined the clinicopathological features associated with the risk and prognosis of DM in thyroid cancer patients (N0), and successfully established and validated a nomogram capable of predicting OS in individual patients with DM. The nomogram is highly useful for the timely identification of thyroid cancer patients (N0) at high risk of DM by physicians, enabling individualized survival evaluations and treatment for TC patients with DM (N0).