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: PATIENTS AND METHODS : Forty - two patients with biopsy - proven prostatic adenocarcinoma [ 26 with stage C ( T3N0M0 ) and 16 with stage D1 ( T3N1M0 ) ] were included in this study .
### Output Text:
PATIENTS AND METHODS : Forty - two patients with biopsy - proven prostatic adenocarcinoma [ 26 with stage C ( T3N0M0 ) and 16 with stage D1 ( T3N1M0 ) ] were included in this study . 