Yes, I agree with what Semiferal said. A blood transfusion may help and it may not. It depends on your cat's current health and how severe the anemia is. A transfusion isn't a cure for anemia.
I would have a long and detailed discussion with your vet. Ask lots of questions. I found it helpful to contact the Cornell Feline Health Center http://www.vet.cornell.edu/fhc/
My FELV cat had very severe anemia and none of the treatments were successful. We did a blood transfusion and it helped him but only for a very short time.
You are in my thoughts. I know how painful it is to lose a cat to FELV.