My dog was diagnosed with mast cell cancer. The ASPCA was good about paying half the cost of her treatment for the first year I had them, but after that they considered the cancer a pre-existing condition and paid nothing more. They explained that their insurance is renewed annually, so anything my dog had the previous insurance year was pre-existing the second insurance year. This was really outrageous to me but there was nothing I knew to do. They were very nice when they rejected my claims. I don't know if I would recommend this company to other pet owners - I think I would as long as they understood and were willing to accept this issue. Perhaps ASPCA has a cancer rider?
Age of Pet