03/09/2026
Preventing unwanted litters is a goal we all share, but it may be time to rethink the surgical approach. Hormone-sparing procedures such as hysterectomy and vasectomy can make dogs sterile while preserving natural hormone balance, and they can often be performed as early as 8 weeks of age.
A large peer reviewed analysis has raised important questions. In this hospital population, spayed female dogs showed roughly 30 to 80 percent higher odds of several cancers compared with intact females. However, age remained the strongest driver of cancer risk overall.
Researchers reviewed medical records from 150,063 dogs and cats seen at the University of California, Davis Veterinary Medical Teaching Hospital between 2000 and 2019. They evaluated which cancers were most common and how risk related to age, breed, s*x, and neuter status.
Spayed female dogs showed higher odds of several cancers compared with intact females:
โข Lymphoid cancer (immune system cancers such as lymphoma): about 80 percent higher odds
โข Mast cell tumor (a common skin cancer from allergy cells): about 60 percent higher odds
โข Melanoma (cancer of pigment cells, often in the mouth or toes): about 40 percent higher odds
Download the free PDF with the latest research surrounding spay & neuter syndrome, link in comments.