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: BACKGROUND : Cisplatin - based chemotherapy combinations improve quality of life and survival in advanced nonsmall cell lung carcinoma ( NSCLC ) .
### Output Text:
BACKGROUND : <span class="chemical">Cisplatin</span> - based chemotherapy combinations improve quality of life and survival in advanced nonsmall cell lung carcinoma ( NSCLC ) . 