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Featuring Demian Dressler, DVM and Sue Ettinger, DVM, Dip. ACVIM (Oncology), authors of The Dog Cancer Survival Guide

Spay/neuter and the association with cancer in dogs: part two

Updated: May 13th, 2019


Spay Neuter Rottweiler: Susan Ettinger, DVM, Dip. ACVIM (Oncology) continues her discussion on how spaying and neutering dogs can increase their risk for certain aggressive cancers.

In part one of my series on spay/neutering, we reviewed the data that sex hormones can promote certain cancers, specifically anal gland tumors in males and breast cancer in females.

But more recently, there is evidence that less exposure to sex hormones increases risk for other aggressive cancers, including osteosarcoma, bladder transitional cell carcinoma, and prostate cancer, lymphoma, and mast cell tumors. So sex hormones may not be all bad, and in fact may be PROTECTIVE again certain cancers.

Osteosarcoma (OSA)

Osteosarcoma (OSA) is the most common bone cancer in dogs, accounting for about 85% of bone cancer cases. It is very aggressive: 90% of patients will die from the metastasis within the 1st year when amputation is the only treatment. Median survival times for OSA cases with amputation and chemotherapy increase to ten to twelve months, with 20-25% of dogs still alive at two years. I’ve recently written a series on OSA, if you want to read more about them.

Here is the rundown on how spay/neutering seems to influence cancer development:

Purebred dogs who have been spayed or neutered are twice as likely to develop osteosarcoma (bone cancer).

Look in the last section of the book for specific recommendations for each of the most common dog cancers, including osteosarcoma!

The risk is even higher for Rottweilers. One study looked at 683 Rotties and showed that both male and female Rotties who were surgically sterilized before the age of one year had an approximately one in four risk for developing osteosarcoma during their lifetime, while intact Rotties were much less likely to develop the disease. Spayed/neutered Rotties were 4 times more likely to develop OSA.

 Prostate Cancer

In a 2002 study, neutered males were 4 times more at risk for prostate cancer than intact males.

Then in 2007, a second study showed castration increases the risk for developing  bladder and prostate cancers by three to four times.

The greatest risk was for prostate transitional cell carcinomas (TCC), with an overall risk of 8.


Spaying has also been shown to increase the risk of lymphoma. Intact females had a significantly lower risk, not just lower than for female spayed dogs, but also lower risk for both intact and castrated males.

Interestingly, in people, women also have a lower risk for lymphoma than men.

Heart tumors

For all types of heart tumors, the relative risk for a spayed female was greater than 4 times that for intact female dogs.

For cardiac hemangiosarcoma (HSA), female spayed dogs were greater than 5 times the relative risk than for female intact dogs. Castrated males were also at slightly greater risk than that for intact males.

In the next post, I will discuss 2 brand new studies looking at the possible protective effect of sex hormones for cancer. The 1st study looks at the effect of neutering on both joint disorders and cancers in Golden Retrievers.

The 2nd study looked at sterilization, which found sterilization increased how long the dogs lived, EXCEPT sterilized dogs were more likely to die of cancer (and immune-mediated disease).

We will also discuss some recommendations on when to spay or neuter your dog. (Yes, I still think spay/neuter is a good idea, but when for your dog?)

Live longer, live well.

Dr Sue

Spay/neuter and the association with cancer in dogs: part one

Spay/neuter and the association with cancer in dogs: part three

Leave a Comment

  1. Gail Dwyer on June 11, 2013 at 10:36 am

    Is there any thought to putting spayed females on hormone replacement therapy to reduce the cancer risks?

  2. Shirley Hoagland on June 7, 2013 at 3:09 am

    This is disturbing news since most adoptable animals from shelters routinely are spayed/neutered as part of the process. Do you think that such ‘practice’ will change in view of this research?

  3. Ann M. McHugh on June 7, 2013 at 1:53 am

    Dr Ettinger- this is what I have been trying to explain to people for the past few years! Can you list the references for some of the newest studies that support your findings? I’m asking to be able to “recite chapter and verse” to those unfamiliar with what newer research is uncovering. When trying to discuss these findings with a person very recently when she was insisting on neutering and giving both rabies vaccination and DHLP other SAME DAY to a 5 month old dog she needed to place, she kept referring to very old(1972, 1982, 1991). Many of her references kept referring back to the same old sources. Her mind was made up, sadly, as she did not trust a new owner to keep the young dog from adding to the shelter population! The fact that she’d place her dog with someone, but not trust them to act responsibly until the safest time for neutering the young male says a lot about the woman. A vet who would do all three things on the same day is NOT a vet open to new findings or concerned about the future health of that young dog. No health checks had been run on the parents of the young dog so the status of hips/elbows and knees should be of concern for potential adopters. Glad you are addressing that aspect of early s/n next time.
    Looking forward to the next installment.

  4. Beth casteli on June 7, 2013 at 1:17 am

    My golden retriever has mast cell cancer. He is a 10 1/2 year old, intact male.

  5. Danielle Carpenter on June 6, 2013 at 5:12 pm

    My Golden had testicular cancer at age 9, recovering nicely, and then cardiac hemangiosarcoma from which he died at age 12. I often wonder if he had not been neutered…..



  6. Pam Wilkinson on June 6, 2013 at 5:01 pm

    I really feel you should start your spay/neuter article with: In the U.S. over 14,000 healthy dogs and cats are killed/euthanized every day simply because they were born unwanted.
    Spay and neuter is the most important so all dogs and cats can live a long healthy life. My dog, Piglet is 18 years old. She was not spayed early actually I found her on the streets with nipples showing she had a litter or more. Wherever her pupsllanded up, if not spayed/neutered can procreate over 30,000 dogs in several years. One female dog and her offspring can procreate 60,000 dogs in 6 years the ASPCA states. Over half will land up at shelters likely to be euthanized or if they land up on the streets they will die miserably.
    The grass fertilizer causes cancer. Your better to tell people don’t use fertilizer and feed your dog greens and healthy food. This prevents cancer as I have learned from you. I want to be removed from future emails as you give the red carpet for people not to sterilize their pet until it’s possibly too late and another unwanted litter is born to be killed. At 4 or 5 months old a female dog and cat can go into heat. They are likely to take off with their sexual drive and be hit by a car. Did you know most male dogs and cats hit by cars are unsterilized? I think it’s because their sexual drive prevented them from being cautious when chasing down an in heat female. They can smell a female in heat up to 6 miles. Please go to a shelter and see their trash dumpster full of dead dogs and cats who were born unwanted then killed. Please focus on how to help pets when they have cancer because there are over 100 ways to get cancer maybe more. By not spaying/neutering and allowing your pet to have a litter or more is certain death for other wonderful dogs and cats and possibly your own unsterilized pet if they smell a neighbors dog/cat in heat. They will dart out doors, jump fences, dig holes, etc. Their sex drive will kill them before cancer gets them.
    Spay today, save lives tomorrow.

  7. Penny on June 6, 2013 at 1:00 pm

    Dr. Sue…. Love reading your blogs and positively loved the Dog Cancer Book… even have my holistic vet encouraging patients to purchase and read this book 😀 I learned so much… many things I wish I had known years ago …. Unfortunately it couldn’t save our Brittany… 🙁 Looking forward to the last installment in this series as my rescue puppy(approx 6m of age we believe) is going to our vet on June 11 for spay discussion and final round of puppy shots. Thank you for your continued writings for us!!!

  8. Anders on June 6, 2013 at 12:10 pm

    Can you reference the studies you are utilizing? I’m curious about the sample sizes and breeds studied. Also, we just brought a golden retriever into our family 4 mths ago who has an undescended testicle…our vet has been monitoring status hoping the condition would change (to no avail as of yet, 6 mths old now) can you comment on this situation as to your recommendation regarding when to neuter I have done research and found numerous articles but no actual scientific papers stating increased cancer risk due to this condition. Thank you, Anders & Aureus! Check up on Latin for the clue as to who is the canine 😉

  9. Jane Winston on June 6, 2013 at 11:47 am

    My last Irish Setter–that I neutered at 1-1/2 years got osteosarcoma. My new Irish Setter was 2 years in April. I was told to wait until he is 2-1/2 before I neuter him (his bone growth plates should be closed by then). Would you advise me to wait even longer (possibly never neuter him)?

  10. Karen Elkin on June 5, 2013 at 2:38 am

    I have a bottle of Apocaps that I purchased for my scottie who was suffering from TCC. Sadly he passed away a couple of weeks ago – I didn’t start the treatment in time. I do have his litter brother so I’m pleased to see that the remaining Apocaps can be given to him as support. I also “manage” the Scottish Terrier Health Network and as you know Scotties are susceptible in a greater degree to TCC than other breeds, so I’m really pleased to subscribe to your blog. I would like to share your health matters with my “followers” if that is ok?

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