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http://healthypets.mercola.com/sites/healthypets/archive/2014/06/13/neutering-spaying-cancer-risk.aspx

New Evidence Shows Link Between Spaying, Neutering and Cancer

June 13, 2014By Dr. Becker

A recent study raises even more questions about traditional spay/neuter practices for U.S. dogs.

The study, titled "Evaluation of the risk and age of onset of cancer and behavioral disorders in gonadectomized Vizslas,"1 was conducted by a team of researchers with support from the Vizsla Club of America Welfare Foundation. It was published in the February 1, 2014 issue of the Journal of the American Veterinary Medical Association.

Like previous research on Rottweilers and Golden Retrievers, the results of the Vizsla study are a call to action to take a closer look at current neutering recommendations.

Vizsla Study Results

The Vizsla study involved 2,505 dogs, and reported these results:

Dogs neutered or spayed at any age were at significantly increased risk for developing mast cell cancer, lymphoma, all other cancers, all cancers combined, and fear of storms, compared with intact dogs. Females spayed at 12 months or younger, and both genders neutered or spayed at over 12 months had significantly increased odds of developing hemangiosarcoma, compared with intact dogs. Dogs of both genders neutered or spayed at 6 months or younger had significantly increased odds of developing a behavioral disorder, including separation anxiety, noise phobia, timidity, excitability, submissive urination, aggression, hyperactivity, and/or fear biting. When it came to thunderstorm phobia, all neutered or spayed Vizslas were at greater risk than intact Vizslas, regardless of age at neutering. The younger the age at neutering, the earlier the age at diagnosis with mast cell cancer, cancers other than mast cell, hemangiosarcoma, lymphoma, all cancers combined, a behavioral disorder, or fear of storms. Compared to intact dogs, neutered and spayed dogs had a 3.5 times higher risk of developing mast cell cancer, regardless of what age they were neutered. Spayed females had nine times higher incidence of hemangiosarcoma compared to intact females, regardless of when spaying was performed, however, no difference in incidence of this type of cancer was found for neutered vs. intact males. Neutered and spayed dogs had 4.3 times higher incidence of lymphoma (lymphosarcoma), regardless of age at time of neutering. Neutered and spayed dogs had five times higher incidence of other types of cancer, regardless of age of neutering. Spayed females had 6.5 times higher incidence of all cancers combined compared to intact females, and neutered males had 3.6 times higher incidence than intact males.

Vizsla Researchers Conclude More Studies Are Needed on the Biological Effects of Spaying and Neutering, and Also on Methods of Sterilization That Do Not Involve Removal of the Gonads.

The Vizsla researchers concluded that:

"Additional studies are needed on the biological effects of removing gonadal hormones and on methods to render dogs infertile that do not involve gonadectomy. Veterinarians should discuss the benefits and possible adverse effects of gonadectomy with clients, giving consideration to the breed of dog, the owner's circumstances, and the anticipated use of the dog."

(The full Vizsla study can be downloaded here.)

I absolutely agree with the researchers' conclusion that studies are needed on alternative methods of sterilizing dogs that do not involve removing the gonads. As I explained in an earlier video, over the years I've changed my view on spaying and neutering dogs, based not just on research like Vizsla study, but also on the

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health challenges faced by so many of my canine patients after I spayed or neutered them. These were primarily irreversible metabolic diseases that appeared within a few years of a dog's surgery.

My current approach is far removed from the view I held in my early days as a vet, when I felt it was my duty and obligation to spay and neuter every dog at a young age. Nowadays, I work with each individual pet owner to make decisions that will provide the most health benefits for the dog.

Whenever possible, I prefer to leave dogs intact. However, this approach requires a highly responsible pet guardian who is fully committed to and capable of preventing the dog from mating (unless the owner is a responsible breeder and that's the goal).

My second choice is to sterilize without desexing. This means performing a procedure that will prevent pregnancy while sparing the testes or ovaries so that they continue to produce hormones essential for the dog's health and well-being. This typically involves a vasectomy for male dogs, and either a tubal ligation or modified spay for females. The modified spay removes the uterus while preserving the hormone-producing ovaries.

The cases in which I opt for a full spay or neuter usually involve an older dog who has developed a condition that is best resolved by the surgery, for example, pyometra (a uterine disease in female dogs), or moderate to severe benign prostatic hyperplasia (an enlarged prostate in male dogs) that is impeding urination and/or causing the animal discomfort. Generally speaking, mature intact dogs have had the benefit of a lifetime of sex hormone production, so the endocrine imbalances we see with spayed or neutered puppies don't occur when dogs are desexed in their later years.

A Word About the Problem of Homeless Pets and Spaying/Neutering

It's important to understand that I'm not advocating the adoption of intact shelter animals to people who may or may not be responsible pet owners. Shelter veterinarians don't have the time or resources available to build a relationship with every adoptive family, so all the animals in their care must be sterilized prior to adoption to prevent more litters of unwanted pets.

Would I prefer that shelter vets sterilize rather than desex homeless pets, so that those animals, too, retain their sex hormones? Absolutely I would. But for the time being, the U.S. shelter system isn't up to that particular challenge, nor are DVMs in this country routinely trained in how to perform anything other than full spays and neuters.

So while I totally agree with the need to sterilize shelter pets, I don't necessarily agree with the method of sterilization being used.

Spaying: The One Procedure That Could Reduce YourPet’s Lifespan by Over 30%

December 30, 2009

A study conducted at the Gerald P. Murphy Cancer Foundation and published in the December, 2009 issue of Aging Cell, has found a correlation between the age at which female rottweilers are spayed and their lifespan.The study compared long-lived female rotties (those with a lifespan of 13 or more years) with a group who lived a usual lifespan of about nine years.

"Like women, female dogs in our study had a distinct survival advantage over males," said the lead researcher David J. Waters, associate director of Purdue University's Center on Aging and the Life Course and a professor in the Department of Clinical Sciences. "But taking away ovaries during the first four years of life completely erased the female survival advantage. We found that female rottweilers that kept their ovaries for at least six years were four times more likely to reach exceptional longevity compared to females who had the shortest lifetime ovary exposure."

Because death from cancer is so prevalent in rottweilers, researchers conducted a subgroup analysis of only dogs that did not die of cancer. This focused research further proved the strong association between intact ovaries and longevity.

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Even in dogs that did not die of cancer, the female rotties that kept their ovaries the longest were nine times more likely to achieve exceptional longevity (13+ years).

Simply put, study results indicate removal of a dog’s ovaries significantly increases the risk for a major lethal disease.

Interestingly, the rottweiler research lines up with findings from another recent study of women who had undergone hysterectomies. In that study, women who lost their ovaries prior to age 50 were at greater risk of death by causes other than breast, ovarian and uterine cancer than women who kept their ovaries until age 50.

Dr. Becker's Comments:

A judgment about when and if you spay/neuter should be based on the breed of your pet, the diet you feed, and its physical, immunological and mental development. There is no universal age that is best for spaying … I firmly believe each dog should be individually evaluated to determine when this procedure should be done.The timing of the surgery should be decided with the help of your holistic veterinarian and input from other seasoned dog owners or breeders.

Methods of Sterilization

There are actually three different surgeries which can render a female dog sterile:1. Spaying, also known as ovariohysterectomy2. Hysterectomy in which only the uterus is removed3. Tubal ligation

Spaying is by far the most common of the three options. This surgery removes the entire female reproductive tract, including ovaries, oviducts, uterine horns and the uterus. Spaying eliminates the source of the hormones progesterone and estrogen and prevents your dog from having twice-yearly heat cycles.

A hysterectomy removes the uterus but leaves the ovaries.

In a tubal ligation, the oviducts are cut and tied off, preventing ova from getting to the uterus or coming in contact with sperm.

Neither hysterectomy nor tubal ligation shuts off hormone production, so your dog will continue to go into heat and can mate with male dogs, but no pregnancy will result.

These latter two methods of sterilization are traditionally much less popular than spaying among both veterinarians and dog owners.

Neutering of male dogs, also known as castration involves surgical removal of both testicles, halting production of both sperm and testosterone. It’s possible to perform a vasectomy on a male dog as an alternative to castration, however, like hysterectomies and tubal ligations for female dogs, it is very rarely done.

The Argument for Spaying and Neutering

An intact female runs the risk pregnancy. Unplanned pregnancies result in unwanted litters of puppies (and kittens), many of which end up as abused, neglected, or abandoned animals.

The crisis of pet overpopulation is a serious one, and it is generally assumed responsible pet owners, animal shelters and rescue organizations will spay or neuter animals in their care to help combat the problem.Pet owners spay or neuter not only for birth control, but also for reasons of convenience and to reduce or eliminate certain future health concerns.

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Spaying of female dogs eliminates the inconvenience and hygiene challenges associated with heat cycles. You don’t have to worry that your spayed dog will try to escape your home in order to mate, and you don’t have to concern yourself with male dogs around your female.

Spaying also removes the potential for false pregnancies and life-threatening uterine infections (called pyometras), and reduces the risk of estrogen-related mammary cancer and tumors of the reproductive tract.

A neutered male dog is less apt to roam or mark his territory anywhere and on everything. He also shows less interest in female dogs in heat. Neutering also removes the risk of testicular tumors, perineal hernias and enlarged prostate glands.

Health Problems Associated with Gonad Removal

Common sense tells us, and research proves there are a number of health benefits associated with the sex hormones (estrogen, progesterone, testosterone) produced by ovaries and testicles. These advantages vary with the age, gender and breed of each animal.

Halting production of these hormones through spaying and neutering has been found to increase the risk of certain specific diseases and conditions in dogs, including:

Hemangiosarcoma, a highly malignant form of cancer, osteosarcoma (bone cancer), and transitional cell carcinoma (bladder cancer), both sexes Prostatic cancer in male dogs Autoimmune thyroiditis and hypothyroidism, both sexes Urinary incontinence and urinary tract infections in females Obesity, both sexes Endocrine dysfunction, adrenal disease

Sterilization Decisions Should Be a Part of a Holistic Approach to Your Pet’s Health and Quality of Life

My professional opinion is there is no one perfect, magic age at which to spay or neuter every pet.

Your dog should be old enough to be considered balanced both physically and mentally. Generally speaking, this balance isn’t achieved until a dog has reached at least one year of age. Although some breeds reach maturity faster than others, many giant breed dogs are still developing at 2 years of age.

Other considerations include your dog’s breed and gender, diet, level of exercise, behavioral habits, previous physical or emotional trauma, existing health concerns, and overall lifestyle.

If you own an intact animal and need to make a spay/neuter decision, I encourage you to first learn all you can about surgical sterilization options and the risks and benefits associated with the procedures.

Talk with reputable breeders and other experienced dog owners, and consult a holistic veterinarian to understand what steps you can take to insure the overall health and longevity of your pet.

This "Routine" Neutering Advice May Boost Your Dog's Risk of Cancer and Joint Disease

June 26, 2013By Dr. Becker

A new study conducted at the University of California, Davis1 further supports a growing body of evidence that spaying or neutering, and the age at which it is done, may increase a dog’s risk of certain cancers and joint diseases.

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The UC Davis researchers point out that the U.S. takes a very different approach to spay/neuter compared to many European countries. In this country, not only are most dogs spayed or neutered, increasingly the preferred timing of the procedure is before the animal is a year old. The motivation is presumably pet population control, and owners are considered responsible only if their pet has been sterilized.

In contrast, in many European countries dogs remain intact and animal health experts do not promote spaying or neutering. In fact, a study of 461 dogs in Sweden reported 99 percent of the dogs were intact. In Hungary, 57 percent were intact, and in the U.K., 46 percent.

The UC Davis study was undertaken, according to the researchers, because“Given the importance of gonadal hormones in growth and development, this cultural contrast invites an analysis of the multiple organ systems that may be adversely affected by neutering.”

Study Looked at the Impact of Spay/Neuter on One Breed, Both Genders, and Five Different Diseases

The UC Davis study looked at the health records of 759 Golden Retrievers. Goldens were chosen because they are one of the most popular breeds in the U.S. and Europe, are often used as service dogs, and are also susceptible to various cancers and joint disorders.

The intent of the study was to investigate the effects of neutering on the risks of several diseases in a single breed of dog, distinguishing between males and females, and between dogs that had been neutered or spayed early (before one year), late (after one year), or not at all.

The dogs ranged in age from 1 to 8 years and had been seen at UC Davis’ William R. Pritchard Veterinary Medical Teaching Hospital for one or more of the following problems: hip dysplasia (HD), cranial cruciate ligament (CCL) tear, lymphosarcoma (LSA), hemangiosarcoma (HSA), and mast cell tumor   (MCT).

The researchers focused on joint disorders and cancers because neutering or spaying removes the testes or ovaries and disrupts production of hormones that play important roles in body processes like bone growth plate closure.

Findings Reveal Significantly Higher Disease Rates in Spayed/Neutered Dogs

The study revealed that for all five diseases, the rates were significantly higher in both males and females that were neutered or spayed (before or after one year of age) compared with intact dogs.

Of special concern is that results showed a 100 percent increase in the rate of hip dysplasia in male Goldens neutered before 12 months of age. Ten percent were diagnosed with the condition, which was double the rate of occurrence in intact males. Past studies have reported a 17 percent increase among all neutered dogs compared to all intact dogs.

Other results:

There were no cases of CCL tears in intact male or female Goldens. In early neutered males there was a 5 percent occurrence, and in early spayed females, an 8 percent occurrence. Almost 10 percent of early-neutered males were diagnosed with lymphosarcoma, which was 3 times more than intact males. Hemangiosarcoma in late-spayed females was 8 percent -- 4 times more than intact and early-spayed females. No intact females had mast cell tumors, but 6 percent of late-spayed females did.

The UC Davis findings are in line with the results of earlier studies, however, it’s the first study to identify a connection between late spaying and mast cell tumors and hemangiosarcoma in female dogs.

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What These Results Mean for Dog Owners

The study authors consider their findings clinically relevant as follows:

"Specifically for Golden Retrievers, neutering males well beyond puberty should avoid the problems of increased rates of occurrence of HD, CCL, and LSA and should not bring on any major increase in the rates of HSA and MCT (at least before nine years of age). However, the possibility that age-related cognitive decline could be accelerated by neutering should be noted2.

For females, the timing of neutering is more problematical because early neutering significantly increases the incidence rate of CCL from near zero to almost 8 percent, and late neutering increases the rates of HSA to 4 times that of the 1.6 percent rate for intact females and to 5.7 percent for MCT, which was not diagnosed in intact females."

According to lead study investigator Benjamin Hart, professor emeritus at the UC Davis School of Veterinary Medicine, “The study results indicate that dog owners and service-dog trainers should carefully consider when to have their male or female dogs neutered.”

Hart goes on to say it’s important to keep in mind that different breeds have different vulnerabilities to various diseases, and the effects of spay/neuter and when it is done very likely vary from breed to breed. The Golden Retriever findings can’t be generalized to other breeds, or dogs in general. However, in other breeds with a propensity for joint disorders and types of cancer different than those prevalent in Goldens, spaying and neutering may increase the risk for those breed-specific disease tendencies.

More breed-specific studies are needed for a full understanding of the disease conditions affected by spaying and neutering.