The role of lymph node status in cancer-specific survival and decision-making of postoperative radiotherapy in poorly differentiated thyroid cancer: a population-based study.

2021 
OBJECTIVE This study aimed to investigate the prognostic value of lymph node (LN) status for patients with poorly differentiated thyroid cancer (PDTC), and to develop a reliable nomogram to predict the 3-, 5- and 10-year cancer-specific survival (CSS) and assist the decision-making of postoperative radiotherapy (PORT). METHODS The Surveillance, Epidemiology, and End Results (SEER) database was utilized to screen eligible patients who were diagnosed between 2004 and 2016. The optimal values of age, metastatic lymph node ratio (LNR), and the number of metastatic lymph nodes (MLN) were determined and incorporated into the construction of a nomogram. The performance of the model was evaluated by generating a calibration curve and calculating the consistency index (C-index). Based on the nomogram, patients were classified into three risk cohorts. The prognostic efficacy of PORT was evaluated in each cohort. RESULTS A total of 522 PDTC patients were included in this study. The LN status-associated parameters (MLN and LNR) were independent risk factors for CSS of PDTC patients. Based on MLN, LNR, and other clinical characteristics (age and T stage), an individualized nomogram was constructed that showed an acceptable predictive performance. Furthermore, we proposed a novel risk-classification system to stratify PDTC patients and to assess the prognostic efficacy of PORT. Only patients in high-risk cohort were found eligible to benefit from PORT. CONCLUSION LN status is statistically associated with the prognosis of PDTC patients. In addition, the individualized nomogram may be a significant tool to assist the evaluation of patients' long-term prognosis and to guide the decision-making for PORT.
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