Great news on getting good results. In regard to telling your Mum, it also depends on how close you live/how often you see her. If your having radiation on a daily basis it might be hard to keep up the facade of what your going through physically and mentally without her knowing. My hubby had prostate cancer which he had lost his father to and he just couldn't tell his Mum, he was lucky to have surgery etc and is in the clear now but he just thought it would be too much stress for her that she didn't need. We also have not told her about my breast cancer. She is in her 80's and has been unwell and we figured that as we are both ok there was no reason to tell her. We live interstate from family so that made the decision easier also.
good look with the rest of your treatment :)