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: The incidence of cardiotoxicity was not higher in patients with signs of cardiovascular disease than in those without in the pre - treatment evaluation .
### Output Text:
The incidence of cardiotoxicity was not higher in patients with signs of cardiovascular disease than in those without in the pre - treatment evaluation . 