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: METHODS : Forty - nine patients with advanced NSCLC were included , 38 of whom were age > / = 70 years and 11 were age < 70 years but who had some contraindication to receiving cisplatin .
### Output Text:
METHODS : Forty - nine patients with advanced NSCLC were included , 38 of whom were age > / = 70 years and 11 were age < 70 years but who had some contraindication to receiving <span class="chemical">cisplatin</span> . 