Treating Homeless Dogs’ Breast Cancer May Shed Light on Human Cancers

dog treatment

Story at-a-glance -

  • The Penn Vet Shelter Canine Mammary Tumor Program helps homeless dogs with mammary cancer to get treatment and make them adoptable
  • Mammary cancer in dogs is similar to breast cancer in humans; the Penn Vet researchers are studying mammary cancer in dogs to further research in human cancer. Focusing on managing excessive estrogen can be beneficial for both species fighting this type of cancer.
  • Dogs have 10 mammary glands and may develop tumors in several of them at the same time; this allows researchers to analyze tumors at different stages of development in the same animal

By Dr. Becker

The University of Pennsylvania runs an innovative program that helps homeless dogs with mammary cancer to get treatment, often saving their lives while at the same time making them adoptable.

Meanwhile, through the Penn Vet Shelter Canine Mammary Tumor Program researchers are also learning more about human breast cancer.

Mammary cancer in dogs is similar to breast cancer in humans. Both are the most common cancers in females of the species (aside from skin cancer) and are fueled by the hormone estrogen.

Mammary cancer tends to be most common among unspayed female dogs, i.e., strays and females used as breeders in puppy mills; among these populations 1 in 4 may have mammary tumors.1

Saving Homeless Dogs' Lives While Furthering Human Cancer Research

The program offers a win-win situation for homeless dogs with mammary cancer, most of which would not otherwise receive needed medical treatment.

About 200 dogs have been treated through the program, including screening to evaluate general health, tumor staging to determine how advanced the tumor is, tumor surgery and follow-up care.

All the dogs have been subsequently adopted or placed in permanent foster care. Meanwhile, opportunities for furthering cancer research abound.

Two studies set to be published soon as a result of the program include one on gene activity in dogs with multiple tumors and another on patterns in connective tissue that may be detected via biopsy.2

The dogs make excellent research subjects for a number of reasons, including the fact that the cancer developed naturally, unlike in rodent studies in which cancer must be artificially induced.

Mammary cancer in dogs also shares many similarities to breast cancer in humans in terms of dietary risk factors, hormonal associations, biology, clinical behavior and more.3

In addition, dogs have 10 mammary glands and may develop tumors in several of them at the same time. This allows researchers to analyze tumors at different stages of development in the same animal. Penn Vet continued:4

"Spontaneous tumors in companion animals represent an untapped resource in cancer research and offer a unique opportunity to study cancer in a natural setting and thus capture the dynamic molecular and biological changes associated with tumor progression as well as the complex interactions between tumor and the microenvironment. Such research may have direct applications to cancer in humans …  

The Penn Vet Shelter Canine Mammary Tumor Program offers an unparalleled opportunity to study cancer in a natural setting and capture the dynamic molecular and biological changes associated with tumor development and progression, as well as the complex interactions between tumor and the microenvironment."

Underlying Causes of Mammary Cancer in Dogs

The work Penn Vet is doing to provide veterinary care to homeless dogs is exemplary. Integrative vets, including myself, also focus on determining the underlying cause of why cancer occurred in the first case.

We can cut cancers out of the body but we can't remove the reason the body allowed cancer to occur unless we work to identify why the immune system failed.

Evaluating environmental chemical load (including unidentified sources of xenoestrogens) is critical for these patients. This cancer is linked to estrogen levels, which can be toxically high in spayed and unspayed dogs as well as castrated males.

Unfortunately, spaying dogs at a very young age does not guarantee the dog won't end up with mammary cancer, as some vets may lead you to believe. This is a picture of one of my mammary cancer patients.

mammary cancer patient

She was a part of an early spay/neuter program at a local shelter (she was spayed before being adopted at 3 months of age). She developed atypical Cushing's (linked to early desexing) and then went on to develop a large mammary tumor.

She was fed a soy-based "hypoallergenic" diet most of her life, which her dad believes, in conjunction with adrenal dysregulation, contributed to her toxically high estrogen levels and, in turn, her cancer. After diagnosing such lumps I typically measure sex hormone levels.

If estrogen levels are elevated, after removing the tumors a protocol including DIM (diindolylmethane) and high-lignan flax hulls may help to naturally reduce estrogen levels.

DIM and flax hulls (not flaxseeds or flaxseed oil) have been shown to promote beneficial estrogen metabolism in both males and females. The body's ability to effectively metabolize estrogen is an important component in the prevention of certain cancers, in particular breast cancer.5

Dietary improvement, including the elimination of all estrogenic foods (including soy and yams) and highly processed foods created via the extrusion process (dry kibble) is important. Watch my video about how the kibble manufacturing process creates carcinogenic byproducts here.

Feeding a fresh, high-fat and no-carb (starch-free) balanced and species-appropriate diet is also necessary and immune-support supplements may be helpful. How do dogs get elevated estrogen levels? Oftentimes it may be due to overexposure to xenoestrogens, which are chemicals that mimic the hormone estrogen. Examples include:

Atrazine (weed killer)

Heptachlor (restricted insecticide)

4-Methylbenzylidene camphor (4-MBC) (found in sunscreen lotions)

Lindane, hexachlorocyclohexane (restricted insecticide)

Butylated hydroxyanisole (BHA) (food preservative)

Methoxychlor (banned insecticide in U.S.)

Bisphenol A (used to make plastics)

Nonylphenol and derivatives (laboratory detergents; pesticides)

Dichlorodiphenyldichloroethylene (DDT)

Pentachlorophenol (restricted biocide in U.S.; wood preservative)

Dieldrin (banned insecticide)

Polychlorinated biphenyls (PCBs) (banned in U.S. but formerly used in electrical oils, lubricants, adhesives and paints)

DDT (banned insecticide in the U.S. but not other countries)

Parabens (lotions)

Endosulfan (banned insecticide in U.S.)

Phthalates (used to make plastics)

Erythrosine (FD&C Red No. 3)

DEHP (found in PVC)

Ethinylestradiol (oral contraceptive)

Propyl gallate (used to preserve oils and fats)

Remember pesticides and chemicals banned in the U.S. still show up on and in products imported from other countries. To reduce your dog's exposure to these estrogen-mimicking compounds, and thereby potentially lower the risk of mammary cancer, I recommend:

Using stainless steel, glass or ceramic food and water bowls

Avoiding plastic storage containers for pet food or water

Avoiding non-stick cookware when cooking food for your pet

Avoiding microwaving pet food in plastic containers

Avoiding the use of DEHA-containing cling wrap

Avoiding pet foods that contain soy and the preservatives BHA and BHT and the food dye FD&C Red No. 3

Using natural pest control around your home and yard

Using alternatives to synthetic flea-repellent products

Using all-natural, non-toxic cleaning supplies inside the house

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