Nomogram for survival prediction in metastatic differentiated thyroid cancer and survival comparison between systemic chemotherapy and local radiotherapy in high-risk patients.

BACKGROUND

Distant metastases are the leading cause of death for patients with differentiated thyroid cancer (DTC), and surgery and radioactive iodine (RAI) therapy are effective treatments for them. However, there remains a large proportion of patients with poor prognoses, and there exists no consensus on whether systemic chemotherapy or beam radiation should be administrated to improve their prognoses.

METHOD: The clinicopathology information of patients with metastatic DTC (mDTC) was retrospectively collected and analyzed. A nomogram was created to predict their prognosis and divided patients into high- and low-risk groups, and the external validation was performed.

RESULTS

The Cox regression showed that sex, age, metastatic sites, surgery, and radiotherapy were independent influencing factors affecting OS. Fine-gray competing risk analysis showed that age, T-stage, N-stage, metastatic sites, and radiotherapy were independent risk factors for TCSD. The nomogram we constructed proved to be effective and robust with high efficiency, with C-indexes of 0.785 (95% CI = 0.752-0.813) and 0.794 (95%CI = 0.766-0.831) on the train and test sets, respectively. mDTC patients were further classified into high- and low-risk groups based on the prediction of nomogram, those in the high-risk group had significantly worse OS and higher TCSD than those in the low-risk group (P < 0.001), and chemotherapy significantly improved OS and reduced TCSD for patients in the high-risk group, whereas local beam radiation did not provide any survival benefit. In the external validation dataset, the 1-, 3-, and 5-year AUC values of the model ranged from 0.833 to 0.873, which further proved the efficiency of our model.

CONCLUSION

This study developed an accurate prognostic model for patients with mDTC, which may be applicable in future clinical practice for prognosis and death prediction. For high-risk patients, as predicted by nomogram, systemic chemotherapy was the recommended therapy option for them.