Quote:
Originally Posted by gemy  Here is the link directly to the Viszlas study. http://mercola.fileburst.com/PDF/Hea...izslaStudy.pdf
On the subject of mammary tumours here is one extract. If you click the link the full 12 page or so report is available to any reader. The association between gonadectomy and various
neoplasms in dogs has been examined in several
studies.15–20 Mammary gland cancer is an important
condition in female dogs, with approximately 20% to
50% of the tumors being histologically malignant.33,34
It is commonly believed that gonadectomized female
dogs have a reduced risk of mammary gland cancer and
that the earlier a dog is gonadectomized, the lower the
risk.28,29,34,35 However, authors of a recent systematic review36
of all reports in peer-reviewed journals on the
associations among neutering, age at neutering, and
mammary gland tumors concluded that the evidence
that neutering reduces the risk of mammary gland neoplasia
is weak and not a sound basis for firm recommendations
on neutering because of limited evidence
and bias in published results.
I would try to copy and paste this report but right now my p.c. is telling me my disc is full
The above finding on Viszlas and no apparent association on age of spaying and relationship to mammary cancer is surprising to me. Most previous research I have read is for slight iincrease in incidence rate associated with spaying before first heat, spaying after first but prior second heat, but a minimal increate in risk/incident rate. How ever a sharp increase in unbred older intact females.
This study I need to look at more to see about pyrometra, which is imo, much more of a concern than mammary cancer is. Of course these two conditions affect predominately female dogs, or solely female dogs. And most studies indicate that pyrometra is rare in young females.
And as the study authors have said much more research is needed to be done not just for Viszlas but for all breeds.
It could very well be that there is a breed disposition to mammary cancer, as there seems to be for sarcomas, hemangiosarcomas, Von Willenbrands disease (which thankfully now there is a genetic test for). If you look at the report on cancers male/females you do not see mammary cancer delineated, and was included in the other types of cancer Mammary cancer was lumped in with all other cancers.
Other cancers including mammary and most specifically by breed type are only suspected, some breeds with strong suspicion that there is not only a breed disposition to, but an association with timing of s/n. So the first question to be answered by science is there a breed disposition to cancer? If so, what kinds and by what breed? Then what causes this breed disposition? Is it truly genetic? Some combo of genetics, nutrition, environment etc. Are all breeds or only certain breeds made more or less susceptible by judicious timing of a full s/n? Would it be better to use alternative methods of s/n to keep the sex hormones? For males, for females, for which breed types?
And having asked all the above questions, which will be decades in the answering, all we as breeders can go by is the best information at the time we need to make the decisions and or recommendations to our puppy owners. And all you can do as pet owners is to educate yourself as well for the breed (s) you own.
Some breeds are further ahead in answering these questions then others. Some answers perhaps mammary tumour and pyrometra is consistent across all or most breed types or sizes.
I await reading and posting new research and findings on this topic.
|
I think that these results could very well be breed-specific, and also related to the types of cancer under discussion. Here is a quote from the article "Pros, Cons, and Techniques of Pediatric Neutering," by Margaret V. Root Kustritz (Vet Clin Small Anim 44 (2014) 221–233), also a 2014 article:
"
Mammary neoplasia For female dogs and cats, the greatest benefits are decreased risk of development of mammary neoplasia when aged and lack of development of pyometra. Incidence of mammary neoplasia in cats is 2.5% and is virtually always malignant adenocarci- noma.22–24 Mammary neoplasia is 7 times more likely to occur in aged queens than in spayed female cats, with the greatest decrease in incidence associated with spaying before the first estrus.24
Incidence of mammary neoplasia in dogs is 3.4%, with about 50% being benign fibroadenomas and 50% malignant adenocarcinomas.22,25–32 Incidence is greatly decreased by spaying, especially by spaying before the first heat.1,33,34 A recent attempt to determine the significance of these data by systematic review of the veterinary literature was unable to identify strong evidence suggesting that spaying decreases the risk of mammary cancer; however, this systematic review is based on work in human medicine and requires a massive body of literature, which does not exist in veterinary medicine.35"