Pyometria ( not sure on spelling) is the infection in the uterus and having a dog spayed before the 1st heat cycle will reduce the chance of cancer in the mammory chain by 90 precent. After the 1st heat cycle the precentage drops greatly. Also neutering a male dog by 9mths reduces the chances of prostrate cancer and cancer in the mammory chain also. male dogs can get mammory cancer just as in humans a man can develope breast cancer. I know my brother is in treatment right now for it. Just remember anything and everything that we as humans get our pets also can get. Liver, Kidney,Heart disease, leukemia, diabetes and the list goes on.