Vets have been encouraged to consider evidence as a whole, rather than studies in isolation, following research claiming neutering can increase the risk of cancer.
One study from the University of California, Davis (UC Davis) investigated hospital records of 759 golden retrievers between the ages of one to eight.
It found three times as many males were diagnosed with lymphosarcoma – the third most common cancer in dogs – as unneutered males.
Findings also indicated the percentage of late-neutered females was four times more than intact or early-spayed canines. A second study published in 2014 from Binghamton University, New York state found similar connections in the vizsla breed.
Research was based on a voluntary internet study of more than 2,500 dogs born between 1992 and 2008, which found correlations between spayed and neutered vizslas and mast cell cancer, lymphoma and hemangiosarcoma – cancer of blood vessel lining.
Canines that had undergone the procedure were also more likely to have behaviour disorders, such as storm anxiety, and researchers claim the younger they were spayed or neutered, the earlier these problems may show.
Neutering is promoted as a responsible part of modern-day pet ownership, but while researchers admit more needs to be done to confirm findings, the studies have prompted concern from dog owners across the UK.
The British Small Animal Veterinary Association (BSAVA) welcomed the studies, claiming findings increased the profession’s knowledge of the risks of neutering, but remained firm the procedure for companion animals should be considered for population control.
A BSAVA spokesman told Veterinary Times: “BSAVA strongly recommends neutering of companion animals should be considered for reasons of population control.
“However, the decision to neuter an individual animal for medical or behavioural reasons needs to take account factors such as breed and age of the animal as well as current and future health status. Any risk benefit analysis can only be based on the evidence currently available. So certainly, these studies add to our knowledge, but more research is needed.
“There has been an increase in evidence about the risks and benefits of neutering – especially with access to large data sets. However, it is important not to look at individual studies in isolation, but to consider the evidence as a whole. While certain risk factors may increase the incidence of particular cancers, it is important to remember these are generally rare conditions and look at absolute numbers affected rather than relative risks.
“These are good studies that add to our knowledge about the risks and benefits of neutering, but both have limitations. The first study (UC Davis) is a retrospective study of clinical records at a university veterinary hospital in California and, therefore, may not be representative even of all golden retrievers in California.
“The second study is based on owner reports to an online survey and may therefore be subject to reporting bias. However, while these sorts of studies can highlight potential risk factors, they do not prove cause and effect, and must be considered in the light of other research. Further research is still needed.”
The full story appears in VT45.11.