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: It was administered by 15 min infusion to 16 evaluable patients with non - small cell lung cancer ( NSCLC ) ( 7 with no prior treatment , 9 patients in relapse following surgery / radiotherapy ) at a dose ( 648 mg / m2 divided over 3 days , repeated every 3 weeks ) determined by phase I trial .
### Output Text:
It was administered by 15 min infusion to 16 evaluable patients with non - small cell lung cancer ( NSCLC ) ( 7 with no prior treatment , 9 patients in relapse following surgery / radiotherapy ) at a dose ( 648 mg / m2 divided over 3 days , repeated every 3 weeks ) determined by phase I trial . 