clear margins

I have squamous cell cancer in my cheek that spread along my facial anerves and has made my left face paralysed.  I can't smile or close my left eye.  MRI shows the cancer but only where there is a  lot in one place.  I recently completed radiotherapy at a good cancer center.  My Dr said that because there is not one compact tumor with clear margins its more likely that they didn't get it alll than that they did.  I'm trying to get through recovery when my Dr tells me that they probably didn't get it all anyway.  I know hes being honest but I wasn't happy to hear that.  Has anyone had a good outcome with a cancer with out clear margins?