One aspect of veterinary oncology that makes it difficult to talk with owners about the expected survival time of their pets is something called “euthanasia bias.” Or, as I like to phrase it, “What one owner will tolerate, another will not.” It’s something that especially confounds my ability to predict a patient’s outcome for a tumor type where a pet’s signs may not be outwardly debilitating, but still markedly noticeable.
As an example, many dogs with nasal tumors are often diagnosed with their cancer after they develop nosebleeds. They may have shown signs of chronic nasal disease for weeks or months prior to developing a nosebleed, but one of the single most prompting events for moving forward with advanced diagnostics necessary to obtain a biopsy of the nasal tissue is the relatively innocuous (though visibly scary) event of a bloody nose.
Owners may tolerate chronic sneezing, snuffling, and noisy breathing from their dog for a long time. They may endure nasal discharge if it’s clear or yellow or green in color. However, the instant blood is seen in the fluid, their level of concern is raised, and they are more likely to seek veterinary attention, or concede to a referral to a specialist for further work up.
Alternatively, it may be that the primary care veterinarian initially treats the pet for an allergy or infection (which occur far more commonly than nasal tumors), but may only suspect a nasal tumor once bleeding starts.
One study of dogs with untreated nasal tumors showed that if a dog experienced a nosebleed prior to diagnosis, their prognosis was shorter than if they were diagnosed before nosebleeds developed.
Nosebleeds in dogs can be dramatic, prolonged, messy, and inconvenient, but are not typically fatal events. So why then do dogs with nosebleeds from nasal tumors live shorter than those that do not develop nosebleeds?
Is it because dogs with nosebleeds have nasal tumors that are truly more aggressive? Does the nosebleed itself indicate a poorer physical status for the patient? Though either answer is reasonable, I believe that euthanasia bias factors largely into play for such cases.
While an owner may endure a bloody nose once in a while, I think it’s much more common that many would consider euthanasia after the first or second episode due to a few factors including (but not limited to):
A perception of a nosebleed indicating a poor quality of life
The urgency seen behind visualization of manifestation of cancer in the form of blood
An intolerance of blood being sprayed over their carpets/walls/etc.
I think the survival time for dogs with untreated nasal tumors that develop nosebleeds is shorter than dogs without nosebleeds simply because the bloody nose is the event that precipitated the diagnosis in the first place.
In other words, dogs with nasal tumors and nosebleeds are more likely to be euthanized than their “non bloody nosed” counterparts, because of the issues associated with the nosebleed in and of itself, rather than anything inherent to the qualities behind the cancer itself. This is the essence of euthanasia bias for our patients.
Euthanasia bias is a unique aspect of veterinary medicine that makes my job just a little bit tougher than I would like. The “gray zone” cases will always be the ones I struggle with the most.
However, it allows me to have a candid conversation with owners about what they could expect as their pet’s cancer progresses. This enables them to start to think about their quality of life issues with a completely different sense of awareness.
Bias isn’t always a bad thing when it comes to pets with cancer – it’s just another challenge we face when fighting against an invariably frustrating disease. In some cases it’s fine to manage the disease chronically, while in others, ending life well before the “line is crossed” is the primary goal.
Your bias may be just the thing that helps you make the best decision for your pet in the end.