Chemo is highly personal. What works in one person may only work partially in another. For some people after an initial response to a drug, it no longer works, and patients switch drugs and try the next one in the list of possible things that might work. Each one may work for some period of time, then cease to. Too often patients run out of options that work at all. Why some disease responds completely to a drug or not is not knowable. Why some diseases adapt to the the chemo and begin to prosper again is also not completely understood. I do not think there is an absolute answer to your question.

Brian, stage 4 oral cancer survivor. OCF Founder and Director. The first responsibility of a leader is to define reality. The last is to say thank you. In between, the leader is a servant.