Neutering significantly increases the risk of bladder and prostate cancer.
Several older studies have shown that the incidence of prostate cancer is increased in neutered males. In 2007, in an attempt to verify the results, yet another study was done on the effects of neutering on the male urogenital tract.
The results were shocking.
Neutered dogs were four times more likely to suffer from malignant bladder cancer than intact dogs.
Neutered dogs were eight times more likely to suffer from prostate transitional cell carcinoma than intact dogs.
They were twice as likely to suffer from prostate adenocarcinoma, and four times as likely to suffer from prostate carcinoma. On average, castrated dogs are three times more likely than their intact counterparts to develop some type of prostate cancer.
However, to keep the situation in perspective, the overall incidence of these cancers is low, around 1-2% of all dogs. Risk can also vary by breed and increases with age.
Neutering obviously eliminates the risk of testicular cancer because, well, the testicles are now gone. Since testicles are a source of the hormone testosterone, the influence of that hormone on the body will be minimized. Benign prostate enlargement is exacerbated by testosterone, as is infection of the prostate, so if your dog develops either of these conditions, he can easily be treated by castration at the time of diagnosis. "Benign" means the condition is not life-threatening, and will improve with treatment. Prostate and bladder cancers, on the other hand, are not as easily treated and may well kill your dog.
Just a bit more information to follow up on the post earlier this month "Rethinking Spay and Neuter". Oddly enough, there are many veterinary websites out there claiming that neutering reduces risk of prostate cancer.
Really? It seems the truth is politically incorrect, or perhaps the truth is just too inconvenient for some people to admit.