6342
Background : Historically , systemic therapy for radioactive iodine ( RAI ) - refractory thyroid cancer has been understudied .
 Chemical: radioactive iodine; Chemical: RAI
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: radioactive iodine; Chemical: RAI