Sandra Zaragoza
Math 1030
Garth Butcher
4 December 2014
What Is The Probability Your Dog Will Have Cancer?
I will be looking at different breeds of dogs and figuring out if there are certain factors that
contribute to a predisposition of cancer in dogs or if health has to do with the diagnoses of cancer. I
chose this topic because I am interested in taking care of dogs and breeding. I plan to approach this
topic by reading academic articles, gathering my data from peer reviewed journals and forming my own
graphs. I will need to figure out what types of formulas I need to use and solve a few simple equations.
Later, I will explain what the data means. My hypothesis is that mongrels, non-purebred dogs will have a
greater disposition to cancer. I do understand that no one thing will be the cause of something. I expect
my conclusion to include multiple factors contributing to the cancer in mongrel breeds.
It is a known fact that most dogs are affected by some kind of disease in their lifetime. The
cancers in dogs that are focused on are histiocytic sarcoma, osteosarcoma, hemangiosarcoma, mast cell
tumors, lymphoma, melanoma, and mammary tumors. Histiocytic sarcomas are very invasive tumors
destroying normal surrounding tissues and have a high rate of spreading to other areas of the body (The
Veterinary Cancer Center.) Histiocytic sarcoma are fairly rare tumors overall but occur with high
incidence in Bernese Mountain dogs, Rottweilers, Flat Coated Retrievers, and Golden Retrievers (The
Veterinary Cancer Center). Osteosarcoma is cancer of the bones. Hemangiosarcoma is cancer of the
spleen (VCC). Mast Cell Tumors or MCT are the most common tumors a dog can have. They occur are
lumps or masses on the dog’s skin (VCC). Lymphoma is when the lymph nodes are enlarged (VCC).
Melanoma is the most common tumor found in the mouth and second most common found in the toes,
there are a few breeds that seem to be more affected than other and they are: Scottish terriers, Cocker
Spaniels, Gordon Setters, Chow Chows, and Golden retrievers (VCC). These tumors usually run to the
bone and have a high rate of spreading. Mammary tumors are breast cancers. These mammary tumors
are most commonly diagnosed in intact female dogs older than 7 years of age. Male dogs can also
develop mammary tumors, but this is rare. Several breeds are more likely than others to developing
mammary cancer and these include: Poodles, English Spaniels, English Setters, and Terriers.
Debbie Selinsky reports on the statistics found in the studies Matthew Breen, a Genomics
Professor at the N.C. State University Center for Comparative Medicine and Translational Research, has
performed on dogs and cancer and how the canine genome sequence is similar to that of people. In this
summary of Breen’s study, we learn that around 50 percent of all dogs over the age of 10 will develop
cancer and about 1 in 4 of all dogs will at some stage in their life develop cancer. Breen points out that
there around 80 million pet dogs in the U.S. and 55 percent of those are purebred dogs. The incidence of
cancer, Breen observes, in purebred dogs is substantially higher than the incidence of people. Golden
Retrievers are one of the most popular breeds in the U.S., Breen focuses on this breed for a brief
moment. 1 in 5 Golden Retrievers will be diagnosed with hemangiosarcoma (which is the most common
tumor of the spleen). Lymphoma is the most common cancer in dogs (Selinsky). Lymphoma causes
death to an estimated 300,000 dogs each year, according to Breen’s findings. For every 100,000 dogs in
the U.S., there are 375 deaths (the rate per year in this situation is: 0.375) 1 in 8 Golden Retrievers will
be diagnosed with Lymphoma (Selinsky). The reason for purebred dogs appearing as a greater target for
cancer, Breen concludes that there are restrictions or “limited genetic variability” when inbreeding
occurs. Breen adds, it is almost guaranteed that the offspring of animals with little genetic variability, it
is more likely to receive mutated copies of genes from their parents. A good example of this problem are
the relatively short life spans of the Bernese mountain dogs. These mountain dogs typically live only 7 to
7.5 years, half of the Bernese mountain dogs will die of a kind of cancer (Selinsky). In comparison to
humans, most dogs will develop lymphoma in middle age. Breen reveals that 85-90 percent of dogs
diagnosed with lymphoma will get treated with chemotherapy and enter remission.
There could be some errors in these numbers, were there surveys that appeared to be like the
census? If so, there could be room for error such as random error or systemic error. Random error holds
a lot of space for human error, writing or reading the incorrect line of data or lying about a breed. The
American Kennel Club now recognizes 180 purebred dogs. Is it possible that what the AKC considers a
purebred dog is a mixture of two dogs? There is a miscellaneous class of dogs on the AKC website, what
if those “purebred” dogs are actually not so “purebred”? What if this mongrel has the genes of a Spanish
Water Dog but it appears to be more of an Old English sheepdog. Surely, most dogs are combinations of
other genes.
In contrast to Matthew Breen’s data, Jasper Copping in “Pedigree dogs…” affirms that Pedigree
dogs are just as healthy as Mongrels. A study done by experts from the Royal Veterinary College
involved an analysis of the medical records of almost 150,000 dogs treated at around 100 vet practices
in the Midlands and the south east from 2010 to 2014. In this research, the experts found that there can
be a large area in prevalence of certain disorders between pedigree breeds. But when purebreds are
compared as a group to crossbreeds, there is no significant difference (Copping). Of the 20 conditions
seen most frequently by vets, only three were significantly more prevalent among pedigrees: ear
infections, obesity and skin growths (Copping). Dr. Dan O’Neill, the one who led this study mentions that
there was no major difference, in the other conditions. Degenerative joint disease which is often said to
be a problem in pedigrees, there was actually a slight tendency for greater problems in crossbreeds, Dr.
Dan O’Neill states. The common idea that crossbreeds are healthier than purebreds is something that
should be looked over, Dr. Dan O’Neill says. “It is not that crossbreeds are healthier overall and it is
wrong to stigmatize purebreds. There isn’t an overall healthier breed, or an overall unhealthier breed –
just variations. In theory, crossbreeds are just combination of their purebred parents and therefore
carry the prevalence you would find in the purebred parents. According to a Journal of Small Animal
Practice in 2010, out of 15,881 dogs 4282 died of cancer. Cancer accounted for 27% of deaths of dogs.
Top Five Breeds
All Deaths
Number of Deaths
Percent (Cancer Deaths/All
(Caused by Cancer)
Deaths)
Irish water spaniel
95
53
55.8%
Flat-coated retriever
610
331
50.3%
Hungarian wirehaired Vizsla
15
7
46.7%
Bernese mountain dog
394
180
45.7%
Rottweiler
137
62
45.3%
In summary, there is no significant difference in the prevalence of certain disorders between
pedigree breeds and crossbreeds. When we take a look at purebreds as a group, there are certain
breeds like the Irish Water spaniel, Flat-coated retriever, Hungarian Wirehaired Vizsla, Bernese
mountain dog and the Rottweiler more likely to die from cancer, we can see that there were purebreds
that have had a greater percentage of cancer-related deaths. 1 out of all 4 dogs will at some time
develop cancer sometime in their lives, the probability here is 0.25. Cancer has the ability to affect
purebreds and crossbreeds. Cancer is not predictable.
Bibliography
Copping, Jasper. "Pedigree Dogs 'as Healthy as Mongrels', Say Vets." The Telegraph. Telegraph Media
Group, 13 Apr. 2014. Web. 30 Nov. 2014.
Dobson, Jane M. "Breed-Predispositions To Cancer In Pedigree Dogs." ISRN Veterinary Science (2013): 123. Academic Search Premier. Web. 29 Nov. 2014.
Selinsky, Debbie. "One Medicine: Dogs, People and Cancer." One Medicine: Dogs, People, and Cancer.
NC State College of Veterinary Medicine, 5 June 2012. Web. 30 Nov. 2014.
<http://www.cvm.ncsu.edu/news/2012-05-05-One-Medicine-Dogs-People-and-Cancer.html>.
The Veterinary Cancer Center:"Cancer in Dogs." The Veterinary Cancer Center. VCC. Web. 30 Nov. 2014.
<http://www.vcchope.com/resource-center/cancer-in-dogs>.
V. J. Adams, K. M. Evans, J. Sampson, and J. L. N. Wood, “Methods and mortality results of a health
survey of purebred dogs in the UK,” Journal of Small Animal Practice, vol. 51, no. 10, pp. 512–524,
2010.