Patients with no tongue do indeed learn to speak again. It obviously will not ever be the same, but it is intelligible and is not the end of the world of conversation with friends and co-workers. It does however take significant practice. There are also surgical reconstructions possible with muscle from other areas of the body, if there is any of the base of the old tongue left from which to obtain blood supply, nerves, and provide and attachment point. I am always somewhat concerned when a surgeon says that they got it all, and there appears to be no continuing treatment with either radiation or chemo. A tumor the size that you are describing likely has had time to put out metastasis to other locations such as the cervical nodes. These may be too small to see in a CT scan or MRI today. Hence the "wash" of radiation or chemo to pick up these micro metastasis. Only patients with carcinomas in situ, or very early stage ones in my opinion get to miss out on the wonderful world of nuclear medicine or chemotherapy. When you hear of oral cancer patients being in recurrence, much of the time this is actually a remaining micrometastasis that was not gotten at the first go around, that has had a year or more to prosper unnoticed in other areas. Having a clean surgical margin is not the same as getting it all in my book.