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: Reduced cardiotoxicity and preserved antitumor efficacy of liposome - encapsulated doxorubicin and cyclophosphamide compared with conventional doxorubicin and cyclophosphamide in a randomized , multicenter trial of metastatic breast cancer .
### Output Text:
Reduced cardiotoxicity and preserved antitumor efficacy of liposome - encapsulated <span class="chemical">doxorubicin</span> and <span class="chemical">cyclophosphamide</span> compared with conventional <span class="chemical">doxorubicin</span> and <span class="chemical">cyclophosphamide</span> in a randomized , multicenter trial of metastatic breast cancer . 