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In DEN + PB treated rats , the survival was prolonged and the tumor incidence decreased as compared with the results obtained by DEN alone .
 Chemical: DEN; Chemical: PB; Disease: tumor; Chemical: DEN
Please list all entity words in the text that fit the category.Output format is "type1: word1; type2: word2". 
Option: Disease, Chemical 
Text: {0} 
Answer:
 Chemical: DEN; Chemical: PB; Disease: tumor; Chemical: DEN