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: STUDY DESIGN : We combined paclitaxel , melphalan and high - dose cyclophosphamide , thiotepa , and carboplatin in a triple sequential high - dose regimen for patients with metastatic breast cancer .
### Output Text:
STUDY DESIGN : We combined <span class="chemical">paclitaxel</span> , <span class="chemical">melphalan</span> and high - dose <span class="chemical">cyclophosphamide</span> , <span class="chemical">thiotepa</span> , and <span class="chemical">carboplatin</span> in a triple sequential high - dose regimen for patients with metastatic breast cancer . 