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

Bladder and prostate cancer: neutering male dogs increases risk

Updated: June 5th, 2019

Oh man. This is going to make a lot of people in my field angry.  Apologies to classmates and veterinarian friends!

I came upon this study from the August, 2007 journal Prostate.  Probably not what a lot of us would be reading in our spare time, but I am busy with upcoming info products for dog cancer owners and I dig through lots of publications.

Here is the study abstract.  The short story is the following:

Data was gathered from North American Veterinary Hospitals on male dogs that had been neutered (testicles surgically removed, or castrated), to evaluate the trend that had been noted in some older articles that neutering increased prostate cancer.

Because, if this were the case (and this is my comment, not the authors’), it would seem ethics demand that owners of male dogs were advised of this before consenting to neutering surgery.

Here is what they found.  Hold your hats, folks:

1. Castration of dogs increases total malignant prostate cancer by over 3 times for some prostate cancers (prostate adenocarcinoma). So the answer is yes, castration does increase prostate cancer in dogs (which goes against what I was taught).

2. Castration of dogs increases the most common type of bladder cancer (transitional cell carcinoma) by eight times.  This is huge!!  Major, major, industry-shaking information, or it should be.

So what does this mean to you are considering castration of your dog (or he is castrated)?

Here are some overall statistics: Roughly 1 in 3 dogs will be affected with some form of cancer, and approximately half of those will die of it, at least based on the treatments that have been available up to this point (I believe we can do a lot better with what I call Full Spectrum Care).  Anyway, 1-2% of all cancers are bladder cancers, the most being transitional cell carcinomas (there are rarely other types of cancer that affects the bladder). So if we put all these above stats together and average them out, we are looking at a bladder cancer risk in castrated dogs of 2 percent.

For more helpful information and tools, get a copy of the Dog Cancer Survival Guide

Two percent is not a lot, but I neuter hundreds of dogs, and I see bladder cancer.  Two percent happens!  And the worst kind of cancer for your dog to get is…the one your dog gets, if you know what I mean.

Here is some information on bladder cancer in dogs.

Okay, the pundit gallery will argue.. but castration helps control the unwanted dog population, helps unwanted behaviors like aggression and territorial urination in undesirable locations, etc.  Yes, yes, all true.

But, we must start informing owners of this, to use Al Gore’s phrase, inconvenient truth before they opt for castration of male dogs.

And that is one of the purposes of this blog!

Best to all,

Dr Dressler


Discover the Full Spectrum Approach to Dog Cancer

Leave a Comment

  1. Christine Taylor on October 1, 2018 at 4:07 pm

    There’s nothing wrong with my dog right now he is 10 and a half American Staffordshire Terrier which is a red nose pitbull he seems to be doing fine no problems but I just want to prepare for the future I feed him pedigree some people don’t agree and I do give him cook chicken breast for extra protein a lot of times I give him tablespoon of peanut butter sometimes and I sprinkle his dog food with granulated garlic my nephew came by and seen him and hadn’t seen him in over a year and he asked me what was wrong with him I told him nothing he said exactly he acts like he’s two years old instead of his age I started adding garlic to his food to help keep the flies and fleas away works great I got the idea from Springtime Incorporated wood sells garlic and vitamins for humans dogs and horses I also did not like using Frontline and those other products on my dogs in order to keep the fleas off garlic was a more healthier route and as you know is an antioxidant good for them and us also I am getting ready to take my dog in to get shots pretty soon hand have blood work done and everything to make sure he’s doing well I’m going to keep reading up and studying on how to keep your dogs healthy and so that way he can have a long life my other staffer he lived to be 14 and a half the one thing I want to know I know that milk thistle is a very strong antioxidant there is one more that is a little bit stronger than that and I can’t remember what that is right now so would it be okay to give my dog the milk thistle when he is taking garlic on his food everyday and I sprinkled the garlic on his food he’s feeding just like you would sprinkling salt on your plate of food any information give me I would appreciate it thank you oh yes I have heard that milk thistle is good to keep from getting liver problems for the dogs

  2. sell d4rksys cc on September 8, 2018 at 2:19 pm

    Wow that was unusual. I just wrote an really long comment but after I clicked submit my comment
    didn’t appear. Grrrr… well I’m not writing all that over again. Anyway, just wanted to say wonderful blog!

  3. DoggieLover777 on June 27, 2016 at 9:59 am


  4. Mei Ling on November 12, 2012 at 10:57 am

    I also have a well behaved loving mixed breed dog that is medium sized & 7 1/2 years old. I rescued him a few months ago & he has bonded beautifully with the children. He looks sum pit bull/plott hound mix probably.

    Vet says yes – prostrate is a bit enlarged & we should think about nuetering him for his health. I am concerned it will change his personality – which is perfect – and /or there will be negative consequences.

    Please advise. I am feeling very uncomfortable with nuetering him at his adult age.

  5. cmntr on November 7, 2012 at 7:07 pm

    What about the fact that a male’s prostate may increase in size with age, if not neutered?? I am having that issue with my 9 year old dog, right now. My vet says neutering helps this to not happen and with my dog, may still help. He has a hard time urinating and has to urinate a lot! So, what is your opinion on what I should do. I’ve also heard that at an older age, the anesthesia could be a problem.

  6. jen on February 7, 2012 at 9:55 pm

    Thank you for an honest opinion about the neutered dogs. I have a 5 yr old shihtzu mix and have missed the ideal age to get him fixed. Everyone pushed him to get fixed but I am a very protective momma so I wanted to know every single risk and benefit. For us, the risks are greater than the benefit so we will not be doing it.

  7. donna on January 20, 2012 at 7:08 pm

    Gosh – reading this blog/article has been refreshing. I have a 11 year old dog that acts like a puppy unless he needs to go. Has been neutured since 10 mos. He has a definite prostate infection (just discovered this after 2 years of him having painful poops) and bladder stones. I know he is 11, but if it wasn’t for this he has all signs of really great health, so not sure what to do. He still cant wait to run agility. Why are dogs so stoic?

  8. Sharath on December 11, 2011 at 8:11 am

    I really need some advise. My male boxer Speeru 10 years old had prostrate gland and when I took him to the Vet, I was advised to castrate my pet. But after castrating him within a fortnight he started developing a lump in his front right leg and limps. The Vet did a fine needle aspirate and tells me he has malignant cancer.
    Is this possible due to neutering? Awaiting your quick response.

    • Dr. Demian Dressler on December 21, 2011 at 8:04 am

      Dear Sharath,
      it is not likely that the surgery actually caused the tumor by itself. As you will read in the Guide, cancers are what is called “multifactorial”, which means a lot of things add up in sequence to bring it on. Yes, it is conceivable that the procedure tipped the scales and brought a developing tumor into existence faster, but I am positive that this was brewing long before hand, just not visible to the naked eye.
      Please be sure to arm yourself with all the tools you need for this cancer.
      All my best

  9. Gilly on December 9, 2011 at 10:52 pm

    My 2 year old dobe has been leaking blood over last day or two and we have a vet appt this moring. After reading this blog, i am very concerned. He hadn’t shown any signs of being ill.He was neutured when he was 7 months at vets advice. I’m hoping it’s just an infection. Have had the worst week, my 7 month old dobe lyla had a horrific accident whilst out walking on wednesday and broke her neck trying to jump a ditch and had to be put to sleep, couldn’t cope with more bad news!!!

  10. Reilly on December 5, 2011 at 4:06 pm

    This doesnt prove that neutering increases chances of cancer. This is correlation, not causation. Unless they actually do an experiment, causation isn’t proven.

  11. Kasandra on July 6, 2011 at 7:59 pm

    Dr. Dressler, I really need some advice. My male Shih-tzu of 7 years old has never been neutered, he’s healthy and the best dog I’ve ever known. I never thought to get him fixed because there was never a worry of him impregnating and females…but recently many people have been telling me to get him fixed to prevent prostate cancer, even me Vet recommends it but I’m not sure what the right thing to do is. Please advise me ASAP what you think is the best thing to do as I made an appt. for him to get fixed for this Friday and I would gladly cancel if you think it best. Thank You

    • DemianDressler on July 13, 2011 at 10:43 am

      Dear Kasandra,
      neutering male dogs does not decrease the risk of prostate cancer. This is incorrect.
      However, there are advantages to it, such as improving other prostate diseases like enlarged prostate (benign but can interfere with urination and passing stool and can be a problem), prostatits, and prostatic abcess.
      The decision to neuter is not a right or wrong one and needs to take into account behavior, anesthetic risk, pet overpopulation, and other health benefits or consequences of neutering. If there is signs of prostate enlargement or infection, I would for sure do it. If not, it honestly is personal preference unless there is clear health benefit or the dog is out there contributing overpopulation or has behavioral issues that need to be addressed.

  12. Bill Vojtech on June 24, 2011 at 3:16 pm

    If you factor in the fact that intact males are more likely to escape and roam in search of females in heat, exposing them to things like traffic, I’d bet it lowers the death rate to neuter them. Also, it entirely eliminates the chance of testicle cancer.

  13. Maggie Sullivan on June 3, 2011 at 4:29 pm

    Thanks so much for this. I have an intact 2 year old male French bulldog, about 28 lbs, on a raw diet, who has an enlarged prostate. Of course everyone is telling me to neuter him, but I don’t want to (and not because we plan to breed — I just figure the hormonal system is there for a reason, right?)

    Can you recommend anything to help shrink his prostate to normal size? I would really appreciate any information you might have on this. Thanks again!

  14. jamie on April 22, 2011 at 4:55 pm

    Hello Dr.D,
    I have a maltese who is about 6 years old and he is not neutuered. I’ve read articles that say a neutered dog lives longer than one that isn’t. Is that true? I’ve also read conflicting articles that say a dog is more likely to get prostate cancer. We have had him for about a year & a half now & hasn’t shown any negative behavior in terms of roaming or spraying. Please help me make the best decision for my pup.

    • DemianDressler on April 27, 2011 at 10:43 pm

      Dear Jamie,
      there are pros and cons to both neutering and not neutering. The standard conventional wisdom suggests to neuter. I do not always agree with the conventional wisdom, but each case must be considered separately.
      Medicine is not always clear cut 🙁

  15. T on April 1, 2011 at 2:13 pm

    Thank you Dr. Dressler for the info on spay and neutering. Unnatural can not be healthy. May I share it?

  16. Rebecca on March 26, 2011 at 5:49 am

    Hello Dr Dressler,
    I was online doing some research on an issue my dog is having. Here it is.
    I was just at my vets office in Wed with one of my working dogs. I had noticed some blood droplets prior. She did a rectal on him to only feel a “lump” on his prostate. We put him on Cipr 250mg’s BID. He will be 7 in May. He is also a GSD approx 92#’s. Not sure what onfo you need. I have also contacted a Repo Specialists and bringing him in next week for exam. Any thoughts? I am very concerned and not ready to loose this dog especially just yet. The Dr I am going to go see is Dr Jane Barber in NC. I am very concerned.

    Thanks so much for all you do!

    • DemianDressler on April 6, 2011 at 8:53 pm

      Dear Rebecca,
      If the antibiotics don’t work you will want to have an ultrasound guided aspirate to get it tested and cultured. This is step two. Hang in there..
      Dr D

    • Melissa on January 26, 2012 at 2:41 pm

      I recently aquired a mixed puppy. He was a stray, but is the nicest dog out there. I am, of course keeping him. Everyone keeps telling me to get him casterated, because it will keep him healthier! So, if the information you are telling me is correct, which I believe it is…I shouldn’t get him casterated correct? He will not be a breed dog, but simply a nice house dog. He is brindle color and has the looks of a lab, mixed with some kind of plott hound. I want him to live a healthy life. If I watch him, to make sure he’s not out breeding other dogs; would you suggest not casterating him?

      • Dr. Demian Dressler on February 8, 2012 at 5:32 pm

        Dear Melissa,
        castration is not a black and white issue. My general opinion is to wait until after 18 months of age unless there is a behavioral or medical reason for it sooner…

  17. Amazing neutering offer.... - Page 2 - Pet Forums Community on January 14, 2011 at 11:23 pm

    […] prostate cancer and bladder cancer, both of which would be much worse than an enlarged prostate. Bladder and prostate cancer: neutering male dogs increases risk A population study of neutering status as a risk f… [Prostate. 2007] – PubMed result […]

  18. Geneva Coats on December 30, 2010 at 7:19 am

    Hi Dr. Dressler,
    Your Sept ’08 post quotes a 3X increased risk of prostate adenocarcinoma for castrated dogs, while the Jan ’09 post quotes that risk as 8X. The Sept ’08 post quotes a risk of 8X higher bladder cancer for castrated dogs while the Jan ’09 post quotes a 4X higher risk. Can you please let me know which is accurate? Thanks!!

    • Alan Arons on January 26, 2012 at 8:48 am

      Thank you for your informative piece on neutering. I am a firm believer of not neutering my pet as I believe it is the owner’s responsibility to maintain the behavior, health and well-being of the pet just like nurturing and fostering a child.

      If the owner isn’t willing to do this, then the person should not have a pet, under any circumstances. I have a 5 year old maltese, who has only mated with another dog once, under the supervision of both owners. Once again, it was the owners who control the situation.

      • Dr. Demian Dressler on February 8, 2012 at 5:30 pm


  19. Geneva Coats on December 30, 2010 at 7:04 am

    Hi Dr. Dressler,
    I notice that you have two entries on this topic. In one entry you state that bladder TCC is increased eightfold in neutered dogs. In the other entry you state three times increase. Then for prostate adenocarcinoma in one article you state 3 increase in neutered males and in the other article it is quoted as 8 times….am I misunderstanding something in your entries?
    I cannot see ANY benefit to neutering males unless people want to alter some specific behaviors like marking….but I’d prefer the marking to needlessly increasing his risk of suffering from a painful and fatal cancer.

    • DemianDressler on January 13, 2011 at 9:06 am

      Here are the study results:
      RESULTS: Neutered males had a significantly increased risk for each form of cancer. Neutered males had an odds ratio of 3.56 (3.02-4.21) for urinary bladder TCC, 8.00 (5.60-11.42) for prostate TCC, 2.12 (1.80-2.49) for prostate adenocarcinoma, 3.86 (3.13-4.16) for prostate carcinoma, and 2.84 (2.57-3.14) for all prostate cancers. Relative risks were highly similar when cases were limited to those with a histologically confirmed diagnosis.

  20. Ariana on December 10, 2010 at 10:08 am

    I am struggling greatly with the decision of having my dog neutered after reading this, and from what Ive heard from most europeans, they seem to be very on track in general, our appt. is Monday, and I think Im going to cancel it.
    On a separate note however, he tested positive for lyme antibodies on the 4dx (inexpensive test} and was treated right away with Doxy, Im thinking of paying the 148. dollars for a more comprehensive test to test his levels of lyme, apres doxy, to see where they are. So much seems to be done backwards…really frustrating, what is your opinion on this, and the use of Frontline. He is a small breed lhasa chihuahua mix, thank you, ariana of cambridge, ma.

  21. Clint KIrk on October 22, 2010 at 8:58 am

    I have a 2 y/o maltese whos is cryptorchid and no vet will take just one. We don’t want him to have px cancer or be incontinent. In adult males (its the same thing.. decreases life expectancy , fatigue etc…etc. Who can I get to remove just one (the undescended one.. obviously at risk due to it’s climate.

    We are in Oklahoma,,,,Lawton,OK

    Clint Kirk, D.O.

  22. Dr. Dressler on March 28, 2010 at 1:41 am

    Dear Denise,
    as always, always work under your vet’s guidance..as to your question, it is difficult to get the high amounts needed by feeding actual mushrooms. A little cooked shitake is one option.

  23. Denise on March 27, 2010 at 8:50 am

    Whenever possible, I prefer my dog’s supplementation to come from fresh food rather than a capsule. Will simply feeding the actual mushroom instead of mushroom extract offer the same benefits to a dog with bone cancer? If so, should the mushrooms be raw or cooked, how much should be fed, and what kinds are best to feed?

    I’ve always thought that mushrooms were toxic for dogs- Is this not an issue?

  24. Jenn Goff on October 7, 2009 at 3:34 pm

    Good evening Dr. Dressler, Tomorrow we have to take our 9 year old Sheltie back to the vet for an ultrasound. He had a UTI at his one year check up in July and was treated with anti biotics. I took him in today for similar issues. They did an x-ray and could see the prostate on a standard xray, this concerned the vet. After reading your blog I am not feeling like I should not have gotten Gretzky neutered at 6 months (the age the vet told me to).

  25. jackie on August 7, 2009 at 3:13 am

    Dr Dressler,
    Thank you for this blog!
    I don’t need to tell you how hard it was to find a vet that tells the
    whole story. We do get caught up in protocol. I understand overpopulation is a horribly serious situation. I just won’t “punish” my dog to solve a problem that has nothing to do with him. Our female Rottie was spayed at 6mos, fearing future cancers and not wanting to breed her. Since she was 2 she has been on Proin for incontinence. : (
    We have had our dogs spayed and neuterd for the health of the dog in the past. But as you write
    there are risks. It is a battle at each vet appointment.
    We have a 3 year old Cane Corso. He is stunningly beautiful.
    And the sweetest dog we have ever had. Our property is fully fenced
    and he hardly leaves our side in the house. : )
    He will keep his testicals, just as we don’t cut off our body parts
    for fear of future possibilities.
    With Gratitude,

  26. Donna Wahlers on October 18, 2008 at 12:00 pm

    Dear DR Dressler: I have been endlessly searching websites on Prostate and TCC in dogs since my 10 yr old lac, Tucker has been diagnosed with both. The first symptoms were only 2 months ago when I noticed him straining to defacate. Within 2 weeks he had a problem urinating and I took him to the vet and he was put on trimeth for a urinary infection. His urinating is now normal , but his prostate was “rock” hard upon his physical exam. Upon my vets reccommendation, I took him to Cornell University in Ithaca, NY and he was examend and given a different type of biopsy. They said something like “small pinging” were send against the prostate instead of a traditional biopsy so cancer cells would not proliferate. They also put him on Proxicam. Also they said the ultasound showed his whole prostate enveloped and enlarged and pressing against his colon, thereby creating his symptom of flat and very small feces. It also showed small tumors or masses on the trigone area of his bladder and both adrenal with abnormal cell growth with blood labs reinforcing their diagnosis of “poor”. I would never want my dear friend Tucker to suffer and evertone says it’s time to think of putting him to sleep which I have done endlessly. but here is my delima. Both regular vet and specialist vet in Cornell said probably few weeks to 2 months tops for Tucker, but since I’ve started him on “K-9 vitamins and Pirocam he has become almost “puppy-like” in his playful behavior and his appetite has increased and his stools are now a little bigger and circular, instead of one-sided flat. I know this is only temporary, but is this maybe because the meds have shrunk his “mass” a little? He is so important to me and I don’t want him to suffer. Will he let me know when it’s time and what can I expect in the end days, so I can minamise his suffering. Thank you, Donna Wahlers

  27. Dr. Dressler on October 13, 2008 at 5:06 pm

    Thanks, yes, this is a “disease of civilization.” Makes sense!
    Best, D

  28. Sylvia on October 13, 2008 at 9:05 am

    It was very interesting to read the article about neutering/spaying. I am originally from Argentina, and have dogs all my life for over 30 years there. We never spayed/neuter our dogs and they never had any cancer; they all died of natural causes, except for our German Shepperd, who had hip displacia. As far as I know, none of my friends or family had cases of cancer in their dogs there either. Spaying and neutering is not as common in Argentina as in the USA and many people I know feed their dogs food scraps of meats and vegetables mostly.

    • Charles on February 20, 2010 at 10:18 am

      Hello Dr. Dressler,

      I hope you don’t mind this question about neutering. I just adopted the most wonderful Corgie mix from a shelter. It is required by law that I have this dog neutered, and so I must do so.

      However, I am heartbroken over what this might do to his personality – he is the perfect little guy. The dog is 2.5 to 3 yrs old. Is there anything you can tell me to allay my anxiety over this procedure? Thank you.

      • Dr. Dressler on February 21, 2010 at 12:44 pm

        Dear Charles,
        at that age, pragmatically, it will probably be okay with respect to the cancer issues. You may want to contact them and find out whether they would allow a vasectomy in lieu of the neuter in this case.
        Best, Dr D

  29. Dr. Dressler on October 11, 2008 at 3:30 pm

    Gina, I am very sorry to hear of your Jack.

    The question answered was concerning spaying of female dogs, which was asked in the previous question.

    The study regarding male dogs did not specify the age of neuter in relation to cancer development.

    Also keep in mind that there are many contributing factors in cancer development, such as carcinogens we are all exposed to whether we like it or not, dietary factors, genetics, emotional/lifestyle factors and more.

    It is rarely a single factor…
    Dr D

    • Lisa on January 27, 2009 at 12:22 am

      We have just had the news that our wonderful boy has an 90% possibilily of having cancer of the bladder (just waiting for lab results to confirm), but the tumour is flat to the wall and about 25% of his bladder wall is affected so they cannot operate. We have just collected him after spending the weekend in emergency hospital after developing a very severe infection and the day at the vets being tested for the cause with this result. He was neutered approx 6 years ago for medical reasons and being a rescue greyhound we are not sure of his age but he is about 11. We have chose not to take the chemo road as I do not want him to be pain so have chose the anti-inflamators & anti-biotics and any other drugs that will help him to ensure he is pain free and happy. It is such a blow that just thinking of it brings me to tears but we will ensure what time he has with us will be extra-special and his rescue sisters (also greyhounds) will be with him.

      • Dr. Dressler on January 30, 2009 at 6:35 pm

        Hang in there Lisa. Send you my best.

  30. Gina on October 8, 2008 at 12:20 am

    “My feeling now is to wait until after a year of age…but less that 2.5 yrs if you opt for it”

    Dr. Dressler, do you mean it is best if going to neuter, that you do so after one year and before 2.5; this must mean the risks if you do it under one and over 2.5 increase. I’ve had both of my dogs neutered lataer in life; Jack was over 4 years when he was neutered and he has bladder cancer now.

  31. Dr. Dressler on October 1, 2008 at 11:16 pm

    Well, do you want the good or the bad??
    Good: it practically eliminates the risk of mammary (breast) cancer.
    And it eliminates the chance of ovarian or uterine cancers (not hugely common).
    Bad: Rotties spayed (and neutered) before one year of age have an approximately 1 in 4 lifetime risk of developing bone cancer later in life. Mixed breed and other breeds’ risk increases too upon early spay or neuter. There are a few other non-cancer related issues to consider, but that is the topic of another blog!
    My feeling is now to wait until after a year of age…but less that 2.5 years if you opt for it.

    • Julia Lewis on January 29, 2009 at 1:54 am

      My spaniel died on Monday. We didn’t know there was anything wrong with him until the New Year, when he suddenly became incontinent. The vet took some x-rays, which showed that the neck of the bladder was much narrower than it should be, but there was no sign of an actual tumour. He put him on anti-biotics and anti-inflammatory steroids but he was going downhill, so he decided there was no other option than to open him up. He did so and discovered that the neck of the bladder was completely thickened with a tumour and that he could not operate, so he put him down.
      My dog had to be neutered this time last year, at the same time that he had a perineal hernia operation. I would never have had him neutered, as I like entire dogs, but the vet said it needed to be done otherwise the hernia wound might burst open again.
      Would this neutering, even so recent, have made him more prone to bladder cancer?
      I am also worried about Frontline, which he had regularly, since I now have read that it could cause bladder cancer.

  32. James on September 30, 2008 at 1:27 pm

    Wow– this is pretty scary news. I was always told that spaying/neutering was the best thing for the HEALTH of my dog. This is sobering information. Do you have info on spaying female dogs as well?