590. Mammary cancer if not spayed by 6 months of age

A lady recently asked me when she should spay her dog? Whether a female spayed dog spayed at 6 months of age will never get breast cancer.

Below is the answer from an American vet, Phil Zeltzman, DVM, DACVS, website
http://www.drphilzeltzman.com/. He published his article
"Common surgeries - critical info you need to know" in Dog Fancy, Sep 2010.

1. The common surgeries are spay, neuter, lumps and bumps and bladder stones.
2. I refer to his spay information

2.1 Some vets in Europe just remove the ovaries in young, healthy female dogs (ovariectomy) - quicker an dless invasive. The uterus shrinks without complications.

2.2 He said that "despite clear scientific evidence to the contrary," some people claim that it is better for a dog to have at least one heat cycle before being spayed. He said "research shows that allowing one heat cycle before being spayed increases the risk of mammary tumours from virtually zero to 8%."

My point is: Many authors give such statistics but none actually quotes the proper research for reference. How many dogs were in the research? Who did the research?

He further stated that spaying after the 2nd heat, incidence of getting tumour is 26%. After 2 years of age, no protection. More than 25% of non-spspayed female dogs develop mammary tumours.

It will be good if Singapore vets can do a study about this 25% statistic or vets can produce proper research reports.

My advice is to spay the female dog 2 months after the first heat to let her develop her vulval area to an adult size. Spaying at 6 months is OK if the owner does not want bleeding. Any reader who knows where the proper research papers are, let me know.