This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Surgery
All agents have been used in drug regimens for the treatment of breast carcinoma. Which one has specific activity in a subset of female breast cancers? 
Select and explain. 
A. Anastrozole, B. Doxorubicin, C. Fluoxymesterone, D. Trastuzumab
D: Trastuzumab
Answer: D: Trastuzumab 
Explanation: Trastuzumab Each of the drugs listed has been used in drug regimens for breast cancer, but only trastuzumab has specificity in its actions. The drug is a monoclonal antibody to a surface protein in breast cancer cells that over express the HER2 protein. Consequently, trastuzumab has value in a specific subset of breast cancers.