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
[{'content': 'Which of the following is the treatment of choice in the management of carcinoma of the anal canal? \nSelect and explain. \nA. Primary radiotherapy, B. Abdominoperineal resection, C. Combined radio-and chemotherapy, D. Neoadjuvant chemotherapy and local excision', 'role': 'user'}, {'content': "Answer: C \nExplanation: A combination of chemotherapy and radiotherapy, so-called chemo radiation (Nigro) is the preferred initial therapy for all anal canal tumours. In such patients a combination of 5 flourouracil and mitomycin is given for approximately 1 week and chemotherapy is followed by radiotherapy, given over 3-7 weeks. Ref: Bailey and Love's Sho Practice of Surgery, 24th Edition, Pages 1269-71.", 'role': 'assistant'}]