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: Pharmacology
[{'content': 'Estrogen positive breast cancer is best treated by which drug? \nSelect and explain. \nA. Tamoxifen, B. Clomifene, C. Glutethemide, D. 5-FU', 'role': 'user'}, {'content': "Answer: A \nExplanation: Ans. is 'a' i.e., Tamoxifen Drugs commonly used in hormone (estrogen) receptor positive breast cancer SERMs Tamoxifen, tromifene SERDs Fulvestrant o Aromatase inhibitors :- Letrozole, anastrazole, exemestone.", 'role': 'assistant'}]