21075
Age greater than 45 years remained a strong risk factor for disease - specific mortality in both FV - PTC and C - PTC , while the presence of extrathyroidal extension and distant metastases were stronger predictors of disease - specific mortality in FV - PTC than in C - PTC .
 None
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: Chemical 
Text: {0} 
Answer:
 None