The Effects of Chemotherapy on Cancer

I lost my brother to cancer he had non Hodgkin's lymphoma it had a huge tumor that grew in his chest. The chemotherapy is designed to kill the fast-growing cells hopefully they kill the fast ones more than the slow ones and if you go to a holistic doctor he does things to get the cells getting your immune system to deal with these fast- growing cells right? I'm really curious to hear your thoughts on cancer because I know that what they were doing to treat him like could have been in a lot of ways what also accelerated the his passing yes but I want to really get down to the root of this issue which is that it's abnormal cell growth of abnormal shaped and functioning