One of our rescue hens, Sprinkles, has the typical tumours (still small enough to be of not much concern) but also cysts. She became so quiet and miserable, prompting a vet trip. He put her on a course of prednisolone (steroid), and she is like a whole new chicken! She's running around and bossing the others about again, it's brilliant to see. The course is due to finish soon so I checked with the vet and he's decided to keep her on it indefinitely. Parrots, raptors etc.. he wouldn't because of the issues of diabetes and other complications brought on by the drug, but he said chickens can somehow handle it better. He had one who they thought they could perhaps help for a couple more months, but she lasted another 4 years with no problems!