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: CONCLUSION : The results indicate a dose - response relationship between cyclophosphamide and the risk of bladder cancer , high cumulative risks in the entire cohort , and also the possibility of risk factors operating even before Wegener ' s granulomatosis .
### Output Text:
CONCLUSION : The results indicate a dose - response relationship between <span class="chemical">cyclophosphamide</span> and the risk of bladder cancer , high cumulative risks in the entire cohort , and also the possibility of risk factors operating even before Wegener ' s granulomatosis . 