I had a double mastectomy , following chemo and then radiation , side affects I had and still have , I was one of the unlucky one that ended with 3 rd degree burns and it damaged my left lung.( but I did have 25 treatments in 4 areas )
So ask how many treatments you are having , as soon as your skin gets sore make sure that the oncologist is aware of it , if you get a registrar ask them to refer to their supervisor for a second opinion, I was silly and trusted what my trainee Dr said and it cost me a week in hospital.
Just ask lots of questions before , during and after, all the best.