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: Patients who are candidates for long - term cyclophosphamide treatment should be routinely evaluated for obstructive uropathy .
### Output Text:
Patients who are candidates for long - term <span class="chemical">cyclophosphamide</span> treatment should be routinely evaluated for obstructive uropathy . 