Keel bone growing prominent in two of my girls

I'm getting worried about two of my girls, even though aside from this they have shown no other health issues. Both are laying fine, both have healthy appetites and regular droppings. They are around 4 years old now, but the last few chickens we had that started going south eventually had keel bones feel a lot more prominently just like they are. The ones that died previously had other signs beforehand- poopy butt, trouble laying, that sort of thing. I just want to know if there's anything I can do- if we go to the vet and it's some kind of cancer, has anybody had a chicken that has survived getting it? :( I know they don't have the longest life, but I would really rather not lose them any sooner than I have to. Picture for attention of my favorite baby