15 years ago with conventional radiotherapy it was about 15%. These days with IMRT it's a rare event, more so in oral cancers, with rates from 0-5%, a little higher with Brachtherapy, and Chemoradiation.
This is another custom island. This one could be used for ads. This spot is one of the best places for ads on your site to be placed. This can be enabled/disabled on a per forum basis.