13255
Among them , aromatase inhibitors ( AIs ) that block the synthesis of estrogens have proven superiority compared with tamoxifen and have replaced it as a first - line hormonal therapy .
 estrogens, tamoxifen
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: Chemical 
Text: {0} 
Answer:
 estrogens, tamoxifen