The objective in the game of Risk is to eliminate all of your rivals.  Because, even when there is just one opponent left, there is a small chance that they could rebuild their army, attack you, and you could eventually loose the game.

It is the same with fighting cancer.  All it takes is for just one cancerous cell to survive all of our attacks on  it (chemotherapy, radiation, drugs, surgical removal, bone marrow transplantation, etc…), it could relapse, and then we could loose our fight against cancer.

The other tricky part about cancer is that it can change.   Cancer cells can mutate, metastasize (spread to other parts of the body), develop resistance to our attacks, and then it becomes impossible to stop.

Jacob Stieler is a cancer patient who's parents are being charged with child neglect because they are refusing to continue the cancer treatment protocol for him.