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: ENT
The treatment of choice of a T1N0M0 glottic carcinoma? 
Select and explain. 
A. Surgery, B. Brachytherapy, C. Chemotherapy, D. External beam radiotherapy
D: External beam radiotherapy
Answer: D: External beam radiotherapy 
Explanation: In T1N0M0 glottic cancer, tumor is confined to the vocal cord with normal mobility without any regional lymph node involvement or distant metastasis. At this stage, the treatment of choice is external beam radiotherapy. It has about 90% cure rate if vocal cord mobility is not impaired. The added benefit of this procedure is that voice production is preserved. In ceain cases if radiotherapy is refused or not available, excision of the cord by endoscopic CO2 laser or laryngofissure is performed.