In the sentence extracted from biomedical literature, identify all the chemical entities. The required answer format is the same sentence with HTML <span> tags to mark up specific entities. 
### Entity Markup Guides:
Use <span class="chemical"> to denote a chemical.

### Input Text: As the precordial pain in this patient was considered to have been due to 5 - FU - induced cardiotoxicity , the administration of 5 - FU was abandoned .
### Output Text:
As the precordial pain in this patient was considered to have been due to <span class="chemical">5 - FU</span> - induced cardiotoxicity , the administration of <span class="chemical">5 - FU</span> was abandoned . 