We are waiting for a bone biopsy. Spur or cancer is the differential diagnosis. We noticed that his previous blood tests showed him slightly anemic. Does that point to cancer?

Not clear. The two choices of possibilities seems a bit unusual. It sounds like the biopsy is to really define the problem in the bone. Anemia can be related to cancer, bur has a very long list of causes. I'm not sure that i can make anything if the anemia.