Chemotherapy is poison and kills cells by poisoning them. It is a chemical and, of course, is unable to tell a cancer cell from a non-cancer cell. That's why a person's hair falls out and they get so sick and vomit, because the chemotherapy kills cells indiscriminately. The explanation the doctor gives to justify using chemotherapy is that the chemotherapy tends to kill the cells that are the fastest growing or the fast-dividing cells, thus it will kill MORE cancer cells than normal cells. And this is true.
Radiation burns out the cancer.
It burns everything in its pathway. It also, like chemotherapy, kills cells absolutely indiscriminately and it destroys the immune system. When the immune system is so severely damaged by chemotherapy or radiation, it can no longer restrain the spread of cancer. Here's another illustration. Of course not.