There are many different tumor types, that is, different types of cancer. Some are hormone dependent/responsive, some are not.
Many cancers produce substances like cachexin, and a host of other identified and unidentified factors which can cause the weight loss and wasting which is so typical of cancers (it will often occur even with no change in caloric/protein intake!) Steroids may be helpful then. Same with the anemia of cancer.
Blanket responses are no good here. Let's first find out what the cancer is (if it indeed even IS cancer), and then go forward.
Natty had leukemia, perhaps that was best for him, this may be an entirely different animal.