The effects depend on dose of chemo, dose of radiation, specific chemo drug(s), type of radiation treatment. For instance, treatment with gamma radiation following chemo and surgery for a myosarcoma will have different effects and dose than for glioma. (With glioma, since survival rates are so low it hardly matters.) Contrast that in turn with radiation for osteosarcoma which would often be delivered by strontium-89. Etc. If you want to understand it better, you can read this book.