20701
The resistance of anaplastic thyroid cancer to radioiodine treatment is principally due to the absence of expression of the sodium iodide symporter ( NIS ) , mainly due to epigenetic silencing .
 Chemical: radioiodine; Chemical: sodium iodide
Please list all entity words in the text that fit the category.Output format is "type1: word1; type2: word2". 
Option: Chemical 
Text: {0} 
Answer:
 Chemical: radioiodine; Chemical: sodium iodide