Multiple doses of radiation to the exact same spot are mostly avoided, though some people have had them done. If you have the radiation map from your previous treatments available, it might even be possible to find pathways to radiate that area and still avoid the same tissues and structures. They are also seeing that with a more targeted approach than even IMRT, Proton beam radiation which is very pin point and less penetrating, that it can have better outcomes if a re radiation has to be done. This is all a difficult decision making place to be, as the documentation of too many grays of radiation to the same area have known negative consequences. Many opt for surgery if it is possible as an alternative, but the places that might be accomplished are limited anatomically.