27353
Based on this intention , cancer chemoprevention generally focuses on the use of nontoxic chemical agents which are well - tolerated for prolonged usage that is necessary to address prostate cancer ' s multistage and lengthy period of progression .
 None
Given options, please tell me the categories of all the listed entity words.Output format is "type1: word1; type2: word2". 
Option: Chemical 
Text: {0} 
 Entities:  
Answer:
 None