Does Spaying and Neutering Increase Cancer Risks?

Once you adopt your dog, one of the first recommendations someone will give you is to spay or neuter. But recent research has found evidence that spaying, or neutering may increase the risk of cancer. Basically, what researchers have found is spaying and neutering reduces the risks of some cancers while increasing the risk of others.

Reducing Breast Cancer in Female Dogs

Spaying female dogs reduces their risk for breast cancer. The sex hormones released by a female dog may increase the risk for mammary cancer. The risk for breast cancer can be significantly reduced by spaying a female dog before she enters her first heat (first heat generally occurs around 6 months of age).

Reducing Testosterone-Based Tumors in Male Dogs

Neutering male dogs reduces their risk of developing testosterone-based tumors. Conditions like perianal adenomas (non-cancerous butt tumor) are stimulated by testosterone. Neutering reduces a male dog’s testosterone levels therefore reducing risk.

There are some breeds who are more likely to develop ‘butt tumors’ than others including:

• Beagles
• Cocker Spaniels
• Shih Tzus
• English Bulldogs

Reducing Testicular Cancer in Male Dogs

Neutering your male dog also eliminates the risk of him developing testicular cancer (since he no longer has testicles).

The Other Benefits to Spay/Neuter

Of course, there are other benefits to spaying and neutering including:

• Behavioral: Humping, marking, aggressive behaviors are reduced
• Population control

There’s Always a Catch

There is a catch here.

Unfortunately, spaying and neutering increases the risk of developing the aggressive types of cancer including:

• Osteosarcoma: Fast-growing cancer which can occur in any bone in the body but often develops in the limbs.
• Bladder transitional cell carcinoma: Cancer of the bladder
• Prostate cancer: Cancer of the prostate in male dogs
• Mast cell tumors: Mast cells are involved in inflammation. Most cells circulate through the body. Mast cells do not circulate but instead are ‘stuck’ in certain tissues commonly within the mouth, nasal passages, lungs, and digestive tract.
• Lymphoma: Aggressive, fast-spreading cancer in the lymphatic cells.

Unfortunately, there isn’t enough evidence to be ‘for or against’ spaying and neutering in veterinary medicine. And, it’s completely your decision whether to spay or neuter your dog. But now you know the facts and can complete some research on your own, too.

Nothing in this article should be construed as financial, legal or veterinary advice. Please consult your own advisors for questions relating to your and your pet’s specific circumstances.