Risk stratification in patients with anaplastic thyroid carcinoma: role of age

Background Thyroid carcinoma is the only cancer that regards age as an important predictor of thyroid cancer-specific survival (CSS). While the 8th American Joint Committee on Cancer (AJCC) staging system raised the age cutoff from 45 to 55 years for differentiated thyroid carcinoma (DTC) to more accurately predict the prognosis, there is no new information regarding the role of age in the prognosis of anaplastic thyroid carcinoma (ATC). The aim of this study was to determine the optimal age cutoff values for mortality risk stratification in ATC patients. Furthermore, a nomogram to predict ATC CSS was developed in each age group. Methods Patients diagnosed with ATC between 2004 and 2015 were identified in the Surveillance, Epidemiology, and End Results (SEER) database. After applying inclusion and exclusion criteria, a total of 1140 patients were enrolled as cohort 1 to describe the characteristics of ATC, while a total of 556 patients were included as cohort 2 to determine age cutoff values for risk stratification by X-tile program. Training set and testing set were randomly generated to develop and validate a predictive nomogram of CSS in each age group. Results The 6-month, 1-year, and 2-year survival was 27.6%, 15.1%, and 6.2%, respectively, in cohort 1. X-tile program results showed that the optimal age cutoff values for mortality risk stratification were 65 and 85 years old (p < 0.001). Distant metastasis was independently associated with CSS in patients younger than 85 years old, and these patients benefited more from complete resection of the tumor and radiotherapy/chemotherapy. However, no predictors of CSS were identified in patients over 85 years old, and interventions (surgery, radiotherapy, and chemotherapy) targeting ATC had little role in disease control in these patients. The nomogram was developed and validated based on the independent CSS predictors in each age group. The C-index values of the training set and testing set were 0.735 [95% CI, 0.696-0.774] and 0.733 [95% CI, 0.663-0.804] for CSS in patients of <= 64 years old, while the values were 0.767 [95% CI, 0.730-0.804] and 0.783 [95% CI, 0.718-0.848] in patients of 65-84 years old. All of the C-index values were larger than 0.7, which showed acceptable prediction performance of the nomograms. Conclusions Age can be used as an auxiliary stratification factor of prognosis in ATC patients. The survival may be improved in patients younger than 85 years old if combination therapy (surgery, radiotherapy, and chemotherapy) was indicated and applicable, while no optimal therapeutic strategy was determined in patients older than 85 years old. The established nomograms can provide good prediction of CSS according to age group.