Over the years, I donated approximately three gallons of blood to the Red Cross. When I was diagnosed with cancer, I immediately became unacceptable. That was 12 years ago and I still receive mail and phone calls asking me to donate. It doesn't matter how often I remind them or request they remove me from their contact list. It is aggravating.
The best advice I can give you is to ignore the requests and don't violate the established protocols. Tell them you have cancer; if you are lying anyway, you might as well get a little sympathy.