I had stage III colon cancer at age 42. I trusted my doctors. I had radiation, chemo and then surgery. Followed by more chemo. 14 years later, I am still cancer free and qualify for the highest rating for life insurance. I had a few side effects, but nothing serious and was given a good prognosis if I participated in the therapy.
It was the right choice for me, for the right cancer, at the right time in my life. If I had a different cancer (such as pancreatic cancer), I may have refused the therapy. If my prognosis was grim even with aggressive therapy, I would not do it. If it was something like a chemo that can change your 6 month survival from 15% to 25%. I think I would go to Disney instead.
Everyone is different, every cancer is different. You get all of the information you can and make the best choice for you and your family. Sometimes you stay in the game, sometimes you have to recognize the inevitable and know when to fold.