As a medical oncologist, I urge you: don't give up!!! I understand your love for your son, but you put your love in a wong direction!!! Yes, the treatment is not easy, and your son will continue to suffer for a few months, even yr. But ALL in children is >90 % curable. You, as a mother, need to be strong to overcome and sustain all this difficult process!!!
Please for your son's future, follow doctor's instruction.