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: Eastern Cooperative Oncology Group performance status improved in 35 % of those patients with an initial value > 0 , whereas relief of at least 1 symptom without worsening of other symptoms was noted in 27 patients ( 55 % ) .
### Output Text:
Eastern Cooperative Oncology Group performance status improved in 35 % of those patients with an initial value > 0 , whereas relief of at least 1 symptom without worsening of other symptoms was noted in 27 patients ( 55 % ) . 