I agree with grtdayn - you have a sister who cares enough to try to encourage you to do what she believes will keep you safe. Don’t listen to her, and protect her from potential guilt over knowing that she encouraged/manipulated you into doing something that ended up bringing back your cancer, or worse. I had breast cancer. I am on meds to keep it from coming back. I fought to beat cancer - as you obviously did, too. I’m not allowing myself to be injected with something that might compromise my fight in any way, shape or form and NOBODY (not even my husband or my children) has the right to ask me to do that for them or anybody else. Her love for you is selfish.