Cancer in dogs

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A 10-year-old female beagle with oral cancer. Cancer beagle.jpg
A 10-year-old female beagle with oral cancer.

Cancer is the leading cause of death in dogs. [1] It is estimated that 1 in 3 domestic dogs will develop cancer, which is the same incidence of cancer among humans. [2] Dogs can develop a variety of cancers and most are very similar to those found in humans. Dogs can develop carcinomas of epithelial cells and organs, sarcomas of connective tissues and bones, and lymphomas or leukemias of the circulatory system. Selective breeding of dogs has led certain pure-bred breeds to be at high-risk for specific kinds of cancer. [1]

Contents

Veterinary oncology is the medical study of cancer in animals, and can be diagnosed and treated by specialized veterinarians called veterinary oncologists.

Causes

Cancer is a complex, multifactorial disease. [2] Carcinogenesis is linked with DNA mutations, chromosomal translocations, dysfunctional proteins, and aberrant cell cycle regulators. [1] Cancer alters the DNA of cells and the mutated genetic material is passed on to daughter cells, resulting in neoplasms. [2] The mutated DNA affects genes involved with the cell cycle, classified as either oncogenes or tumor suppressor genes. [2] Oncogenes are responsible for cell proliferation and differentiation. [2] Oncogenes responsible for cell growth are overexpressed in cancerous cells. Tumor suppressor genes prevent cells with erroneous cell cycles from replicating. [2] Cancer cells ignore cell cycle regulators that control cell growth, division, and death. [2]

The histology of spontaneous tumorigenesis in canines is attributed to the multiplicity and complexity of the disease. The heterogeneity of its development encompasses inherited, epigenetic, and environmental factors. [2] [3]

The selective breeding techniques used with domestic dogs causes certain breeds to be at high risk for specific cancers. Selection for specific phenotypes in dog breeding causes long-range linkage disequilibrium in their DNA. [1] Certain areas of alleles have the tendency to separate less frequently than normal random segregation, which leads to long ranges of repeated DNA sequences. These repeated sequences caused by decreased genetic diversity within breeds, can lead to a high prevalence of certain diseases and especially cancer in breeds. It is believed that the breeding and inbreeding of domesticated canines for specific traits has significantly decreased nucleotide diversity in many pedigree dogs, making certain varieties of canines more susceptible to developing cancer. [4]

Symptoms

Symptoms of cancer in dogs may include:

Types of cancer

Dogs can develop many of the same types of cancer as humans. Many canine cancers are described with the same terminology and use the same classification systems as human cancers. [1]

Hemangiosarcoma is a type of cancer that develops almost exclusively in dogs, the only two other species known to have it are cats and horses. Hemangiosarcomas are tumors that form on the blood vessels, and can occur all over the body. These tumors can develop on the skin, subcutaneously, or on a blood vessel within an organ and are highly malignant. The tumors are most fatal when they rupture, causing the dog to suffer from severe loss of blood, or hypovolemia. [5]

Dogs are one of three mammalian species that are known to suffer from a transmissible cancer. [6] Canine transmissible venereal tumor (CTVT) is species specific and highly contagious. [6] The cancerous cell lines are transmitted between individuals that are in close contact with each other through acts of intercourse, biting, scratching, or licking. [6] The cancer is prevalent in populations of stray dogs or environments of uncontrolled copulation. [6] The tumors occur around the area of external genitalia and can grow up to 15 cm in area. [6] Canine transmissible venereal tumors can often be infected, ulcerated, and hemorrhagic. [6]

Susceptibility

Cancer prevalence in dogs increases with age and certain breeds are more susceptible to specific kinds of cancers. Millions of dogs develop spontaneous tumors each year. [1] Boxers, Boston Terriers and Golden Retrievers are among the breeds that most commonly develop mast cell tumors. Large and giant breeds, like Great Danes, Rottweilers, Greyhound and Saint Bernards, are much more likely to develop bone cancer than smaller breeds. [1] Lymphoma occurs at increased rates in Bernese Mountain dogs, bulldogs, and boxers. [1] It is important for the owner to be familiar with the diseases to which their specific breed of dog might have a breed predisposition. [3]

A study of 144 female dogs found that dogs eating higher amounts of red meat, especially beef and pork, were more likely to get mammary cancer. [7] [8]

Spayed female dogs are less likely to develop cancers affecting the mammary glands, ovaries, and other reproductive organs. [9] [ page needed ] However, neutering increases the risk of prostate cancer in males, [10] and osteosarcoma and hemangiosarcoma in either sex. [11]

Treatment

Treatment options vary and depend on the type and stage of cancer. Common treatments include surgery, chemotherapy, radiation therapy, amputation, and immunotherapy. A combination of therapies may be used. Knowledge and treatment of cancer have increased significantly in the past three decades. Survival rates have also increased due to the increased prevalence of canine cancer treatment centers and breakthroughs in targeted drug development. Canine cancer treatment has become an accepted clinical practice and access to treatment for owners has widely expanded recently. [2] Cancer-targeting drugs most commonly function to inhibit excessive cell proliferation by attacking the replicating cells. [5]

There is one canine tumor vaccine approved by the USDA, for preventing canine melanoma. [12] The Oncept vaccine activates T-cell responses and antibodies against tumor-specific tyrosinase proteins. [12] There is limited information about canine tumor antigens, which is the reason for the lack of tumor-specific vaccines and immunotherapy treatment plans for dogs. [12]

Success of treatment depends on the form and extent of the cancer and the aggressiveness of the therapy. Early detection offers the best chance for successful treatment. The heterogeneity of tumors makes drug development increasingly complex, especially as new causes are discovered. No cure for cancer in canines exist. [2]

Some dog owners opt for no treatment of the cancer at all, in which case palliative care, including pain relief, may be offered. Regardless of how treatment proceeds following a diagnosis, the quality of life of the pet is an important consideration. In cases where the cancer is not curable, there are still many things which can be done to alleviate the dog's pain. Good nutrition and care from the dog's owner can greatly enhance quality of life. [3]

Prognosis

According to Blue Cross, pet owners can expect for their pet to live about 12 months with current treatments. If the owner opts for palliative care instead of treatment, the dog will live about 3 months, although if the tumor is partially removed this can be extended. The survival time may be longer in large dogs, and the cure rate is 20%. If a tumor is completely removed, usually the pet will receive small doses of radiation in hopes of preventing recurrence. The survival rates are: 1 year: 59%, 3 year: 40%, 5 year: 13%. [13]

Related Research Articles

<span class="mw-page-title-main">Osteosarcoma</span> Cancerous tumour in a bone

An osteosarcoma (OS) or osteogenic sarcoma (OGS) is a cancerous tumor in a bone. Specifically, it is an aggressive malignant neoplasm that arises from primitive transformed cells of mesenchymal origin and that exhibits osteoblastic differentiation and produces malignant osteoid.

<span class="mw-page-title-main">Hemangiosarcoma</span> Medical condition

Hemangiosarcoma is a rapidly growing, highly invasive variety of cancer that occurs almost exclusively in dogs, and only rarely in cats, horses, mice, or humans. It is a sarcoma arising from the lining of blood vessels; that is, blood-filled channels and spaces are commonly observed microscopically. A frequent cause of death is the rupturing of this tumor, causing the patient to rapidly bleed to death.

Neutering, from the Latin neuter, is the removal of a non-human animal's reproductive organ, either all of it or a considerably large part. The male-specific term is castration, while spaying is usually reserved for female animals. Colloquially, both terms are often referred to as fixing. In male horses, castrating is referred to as gelding. An animal that has not been neutered is sometimes referred to as entire or intact.

<span class="mw-page-title-main">Pyometra</span> Medical condition

Pyometra or pyometritis is a uterine infection. Though it is most commonly known as a disease of the unaltered female dog, it is also a notable human disease. It is also seen in female cattle, horses, goats, sheep, swine, cats, rabbits, hamsters, ferrets, rats and guinea pigs. Pyometra is an important disease to be aware of for any dog or cat owner because of the sudden nature of the disease and the deadly consequences if left untreated. It has been compared to acute appendicitis in humans, because both are essentially empyemas within an abdominal organ.

<span class="mw-page-title-main">Canine transmissible venereal tumor</span> Histiocytic tumor of the external genitalia of the dog and other canines

A canine transmissible venereal tumor (CTVT), also known as a transmissible venereal tumor (TVT), canine transmissible venereal sarcoma (CTVS), sticker tumor and infectious sarcoma, is a histiocytic tumor of the external genitalia of the dog and other canines, and is transmitted from animal to animal during mating. It is one of only three known transmissible cancers in mammals; the others are devil facial tumor disease, a cancer which occurs in Tasmanian devils, and contagious reticulum cell sarcoma of the Syrian hamster.

<span class="mw-page-title-main">Dog health</span> Health of dogs

The health of dogs is a well studied area in veterinary medicine.

<span class="mw-page-title-main">Lymphoma in animals</span> Type of cancer in animals

Lymphoma (lymphosarcoma) in animals is a type of cancer defined by a proliferation of malignant lymphocytes within solid organs such as the lymph nodes, bone marrow, liver and spleen. The disease also may occur in the eye, skin, and gastrointestinal tract.

<span class="mw-page-title-main">Mammary tumor</span>

A mammary tumor is a neoplasm originating in the mammary gland. It is a common finding in older female dogs and cats that are not spayed, but they are found in other animals as well. The mammary glands in dogs and cats are associated with their nipples and extend from the underside of the chest to the groin on both sides of the midline. There are many differences between mammary tumors in animals and breast cancer in humans, including tumor type, malignancy, and treatment options. The prevalence in dogs is about three times that of women. In dogs, mammary tumors are the second most common tumor over all and the most common tumor in female dogs with a reported incidence of 3.4%. Multiple studies have documented that spaying female dogs when young greatly decreases their risk of developing mammary neoplasia when aged. Compared with female dogs left intact, those spayed before puberty have 0.5% of the risk, those spayed after one estrous cycle have 8.0% of the risk, and dogs spayed after two estrous cycles have 26.0% of the risk of developing mammary neoplasia later in life. Overall, unspayed female dogs have a seven times greater risk of developing mammary neoplasia than do those that are spayed. While the benefit of spaying decreases with each estrous cycle, some benefit has been demonstrated in female dogs even up to 9 years of age. There is a much lower risk in male dogs and a risk in cats about half that of dogs.

The dog is a domesticated descendant of the wolf. Also called the domestic dog, it is derived from the extinct Pleistocene wolf; the gray wolf is the dog's closest living relative. The dog was the first species to be domesticated by humans. Experts estimate that hunter-gatherers domesticated dogs more than 15,000 years ago, which was before the development of agriculture. Due to their long association with humans, dogs have expanded to a large number of domestic individuals and gained the ability to thrive on a starch-rich diet that would be inadequate for other canids.

<span class="mw-page-title-main">Anal sac adenocarcinoma</span> Malignant tumor found in dogs

An anal sac adenocarcinoma is an uncommon and aggressive malignant tumor found in dogs that arises from the apocrine glandular tissue of anal sac. The disease exists in cats as well, but is much less common in that species. They are the second most common cancerous cause of hypercalcaemia in dogs, following T-cell lymphoma.

Canine reproduction is the process of sexual reproduction in domestic dogs, wolves, coyotes and other canine species.

A transmissible cancer is a cancer cell or cluster of cancer cells that can be transferred between individuals without the involvement of an infectious agent, such as an oncovirus. The evolution of transmissible cancer has occurred naturally in other animal species, but human cancer transmission is rare. This transfer is typically between members of the same species or closely related species.

<span class="mw-page-title-main">Aging in dogs</span>

Aging in dogs varies from breed to breed, and affects the dog's health and physical ability. As with humans, advanced years often bring changes in a dog's ability to hear, see, and move about easily. Skin condition, appetite, and energy levels often degrade with geriatric age. Medical conditions such as cancer, kidney failure, arthritis, dementia, and joint conditions, and other signs of old age may appear.

<span class="mw-page-title-main">Veterinary oncology</span>

Veterinary oncology is a subspecialty of veterinary medicine that deals with cancer diagnosis and treatment in animals. Cancer is a major cause of death in pet animals. In one study, 45% of the dogs that reached 10 years of age or older died of cancer.

Cancer in cats is the leading cause of death among cats. It is caused by uncontrolled cell growth, and affects a wide range of cell types and organs in the body. Feline cancer initially manifests as a lump or bump on any parts of the body. It rapidly grows in the affected cell, attaches itself to the tissue under the skin in that area, and, depending on the tumour, it can spread to other parts of the body. Although cancer accounts for approximately 32% of deaths in cats over ten years old, it can be successfully treated if diagnosed early.

The most common bone tumor is called osteosarcoma, and typically affects middle-age to older dogs of large and giant breeds. Osteosarcoma is less common in cats. Osteosarcoma is an aggressive cancer that can develop in any bone of the body but the majority is seen in the limbs.

Many types of skin tumors, both benign (noncancerous) and malignant (cancerous), exist in cats and dogs. Approximately 20–40% of primary skin tumors are malignant in dogs and 50–65% are malignant in cats. Not all forms of skin cancer in cats and dogs are caused by sun exposure, but it can happen occasionally. On dogs, the nose and pads of the feet contain sensitive skin and no fur to protect from the sun. Also, cats and dogs with thin or light-colored coats are at a higher risk of sun damage over their entire bodies.

<span class="mw-page-title-main">Aggressive lymphoma</span> Medical condition

Aggressive lymphoma, also known as high-grade lymphoma, is a group of fast growing non-Hodgkin lymphoma.

<span class="mw-page-title-main">Vegetarian and vegan dog diet</span> Adequate meat-free or animal-free nutrition

As in the human practice of veganism, vegan dog foods are those formulated with the exclusion of ingredients that contain or were processed with any part of an animal, or any animal byproduct. Vegan dog food may incorporate the use of fruits, vegetables, cereals, legumes including soya, nuts, vegetable oils, as well as any other non-animal based foods.

References

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  2. 1 2 3 4 5 6 7 8 9 10 Pang, Lisa Y.; Argyle, David J. (2016). "Veterinary oncology: Biology, big data and precision medicine" (PDF). The Veterinary Journal. 213: 38–45. doi:10.1016/j.tvjl.2016.03.009. hdl: 20.500.11820/0671e750-5fde-4e2e-8951-4d5c78c1a2ce . PMID   27240913.
  3. 1 2 3 4 "Pet Care Cancer". ASPCA. Archived from the original on 2014-12-13.
  4. Dobson, Jane (2013). "Breed-Predispositions to Cancer in Pedigree Dogs". ISRN Veterinary Science. 2013: 941275. doi: 10.1155/2013/941275 . PMC   3658424 . PMID   23738139.
  5. 1 2 Pang, L. Y.; Argyle, D. J. (2015). "The evolving cancer stem cell paradigm: Implications in veterinary oncology". The Veterinary Journal. 205 (2): 154–60. doi:10.1016/j.tvjl.2014.12.029. PMID   25634078.
  6. 1 2 3 4 5 6 Ganguly, B (2013). "Canine transmissible venereal tumour: a review". Veterinary and Comparative Oncology. 14 (1): 1–12. doi:10.1111/vco.12060. PMID   23981098.
  7. Alenza, Dolores Pérez; Rutteman, Gerard R.; Peña, Laura; Beynen, Anton C.; Cuesta, Pedro (1998). "Relation between Habitual Diet and Canine Mammary Tumors in a Case-Control Study". Journal of Veterinary Internal Medicine . 12 (3): 132–139. doi: 10.1111/j.1939-1676.1998.tb02108.x . ISSN   1939-1676. PMID   9595373. The intake of homemade meals (compared to that of commercial foods) was also significantly related to a higher incidence of tumors and dysplasias. Other significant risk factors were a high intake of red meat, especially beef and pork (...) We found mammary tumor risk to be positively associated with the intake of red meat and negatively associated with the intake of poultry meat. Particularly, the intake of red meat emerged as an independent factor associated with the risk in the multivariate analysis. Epidemiologic studies have revealed an association between human breast cancer and the consumption of beef and pork and meat; and sausage, eggs, and meat. However, we have not found an association between consumption of vegetables and fruits and mammary tumor development. Higher consumption of vegetables and fruits is associated, although not universally, with a decreased risk of cancer at most sites in humans, especially epithelial cancers of the alimentary and respiratory tracts. The intake of crude fiber, carotene and vitamin C, and fruits and vegetables has been inversely associated with breast cancer risk
  8. Attwood, Diana. "Infopet - Dogs and diet". www.infopet.co.uk. Retrieved 2021-10-21.
  9. Morrison, Wallace B. (1998). Cancer in Dogs and Cats (1st ed.). Williams and Wilkins. ISBN   978-0-683-06105-5.
  10. Johnston, SD; Kamolpatana, K; Root-Kustritz, MV; Johnston, GR (Jul 2000). "Prostatic disorders in the dog". Anim. Reprod. Sci. 60–61: 405–415. doi:10.1016/S0378-4320(00)00101-9. ISSN   0378-4320. PMID   10844211.
  11. Root-Kustritz MV (Dec 2007). "Determining the optimal age for gonadectomy of dogs and cats". JAVMA. 231 (#11): 1665–1675. doi: 10.2460/javma.231.11.1665 . ISSN   0003-1488. PMID   18052800. S2CID   4651194.
  12. 1 2 3 Regan, D; Guth, A; Coy, J; Dow, S (2016). "Cancer immunotherapy in veterinary medicine: Current options and new developments". The Veterinary Journal. 207: 20–8. doi:10.1016/j.tvjl.2015.10.008. PMID   26545847.
  13. "Cancer in Dogs | Symptoms and treatment".