Quote:
Originally Posted by concretegurl  I've never heard of "any" heats increasing mammary cancer though |
Actually, it is well documented that early spaying significantly decreases the risk of mammary cancer.
When an ovariohysterectomy (OHE) is performed prior to the first heat period in a female dog, the risk of mammary cancer later in life is less than 1%. When OHE is performed between the first and second heat periods the risk is about 8% of mammary cancer later in life. Anytime after the second heat period the risk of mammary cancer in female dogs is about 25%, whether an OHE is performed later, or not.
Canine Spay Mammary (breast) cancer Females spayed prior to their first estrus cycle have a significantly reduced risk of developing mammary cancer, a common cancer in unspayed females. The chances of developing this cancer increase if a female isn’t spayed until after her second heat cycle, but they still remain lower than the risk for unspayed females. So if your dog has already gone through her first heat cycle, it’s not too late. Spaying her will still reduce her risk of developing cancerous mammary tumors.
ASPCA - Virtual Pet Behaviorist - How Will Spaying Change My Dog? A female dog spayed before her first heat will have a near zero chance of developing mammary cancer. After the first heat, this incidence climbs to 7% and after the second heat the risk is 25% (one in four!). It is easy to see that an early spay can completely prevent what is frequently a very difficult and potentially fatal form of cancer. The Canine Spay