How rapid is the final decline in a dog with a brain tumor?

After my parents’ dog passed following a sudden rapid decline from a brain tumor, I consulted with Dr. Peter Gordon, DVM, Dipl. ACVIM (Neurology), with Boundary Bay Veterinary Specialty Hospital in Langley, British Columbia.

My parents’ dog had almost died at the hands of conventional treatment, and we had then turned him over to an alternative DVM cancer specialist.

However, the dog eventually had to be put down, despite the excellent treatment he had, and despite the raving reviews that other dog owners (whose dogs had cancer) had about this second doctor’s treatments.

At the start of the alternative treatment, my brother reminded us that a brain tumor is a serious condition.

The dog had improved considerably with the alternative treatment, and then literally out of the blue, he went downhill to the point where we decided it best to have him euthanized.

We were blindsided and stunned at this sudden, unexpected turn for the worse. We never saw it coming.

How rapid can brain tumor progression be in a dog whose treatment is no longer effective?

Dr. Gordon explains, “This is a difficult question to answer, as there are simply too many variables to consider. Primarily, the location and type of brain tumor will have a dramatic effect on how long a tumor will take to affect or re-affect a patient.”

“Very benign tumors in non-vital locations could take a long time (months) to cause clinical signs, as there is more room to grow, and loss of a non-life threatening function may not be initially noticed.

“Conversely, a very aggressive fast growing tumor, a tumor that is very close to a vital nerve center, or a tumor that has metastasized (spread) to more than one location within the brain will not take very long to create a life-threatening condition and may disable a patient within days to weeks.”

Our dog’s sudden reappearance of signs did not suggest a life-threatening course; but did suggest that this was the end, and that if we didn’t have him euthanized, then perhaps there would be an immediate life-threatening situation — for all we knew, the brain tumor was encroaching upon the brain stem.

Dr. Gordon continues, “Second, many times initial ‘symptoms’ are missed by the family, as a dog cannot describe a headache, dizziness, memory loss, etc.

“As such, the decline may seem ‘out of the blue,’ but in fact, the reported change only represents the final stages of a slowly developing deterioration.”

The vet tech for our dog’s original veterinary neurologist, who had diagnosed the animal, told me early on that eventually, there would be a noticeable deterioration, and that it would be “rapid,” perhaps over a matter of “a few days.” This was frightening to hear.

Dr. Gordon explains, “Third, treatment side effects can play a role in the ultimate survival time, as conditions like delayed radiation necrosis can occur after an initial ‘successful’ treatment and may result in further brain damage/deterioration.

“Fourth, the presence of brain tumors can trigger other conditions such as blood clots, bleeding, cysts, hydrocephalus or intracranial swelling (inflammation) that can develop quickly, compound the effect of the tumor and ultimately lead to the patient’s deterioration.”

Though I am not a veterinarian myself — based on logic, common sense and my knowledge of our dog’s situation and what the diagnosing veterinarian had explained at the outset — I’m concluding that intracranial swelling was what caused the sudden decline.

It wasn’t necessarily the brain tumor itself, but fluid, created by the mass, invading surrounding brain tissue, disrupting the dog’s cognitive functioning.

In theory, we could have had this fluid drained and bought some more quality time with the dog. But for how long?

The first vet’s treatment involved an anti-inflammatory (dexamethasone, which helped reverse inflammation caused by the cancer), and a diuretic (which helped drain fluid buildup from the tumor).

But the dexamethasone, according to the second, alternative vet’s comprehensive testing, had “shut down” the animal’s adrenal and thyroid glands, and had made the dog so hungry that he functioned as not much more than a perpetually famished life form constantly seeking out food.

The alternative vet took him off the dexamethasone, and for the next month and a half, we had pretty much our wonderful German shepherd back.

Until one morning at 5:45 a.m. when I was awakened (I was living with my parents to take charge of the dog’s treatments) by a horrible thud: the dog was seizing…and from that point on, deteriorated.

“As such, the location, type and number of brain masses would need to be known in addition to whatever treatment modalities had been used if one were to attempt to define a prognosis or plausible survival time line for a given patient,” says Dr. Gordon.

“With these sorts of variables involved, each case must be assessed and/or defined on an individual basis by your neurologist.”

If your dog has a brain tumor and seems to have made remarkable progress, don’t take it for granted! That awful turn could occur at a moment’s notice.

Do not become complacent and smug that your dog is cured just because he’s free of signs and looks “normal.”

Don’t put off taking those pictures of him or buying that special treat, and don’t put off hugging and kissing him because you think the “brain tumor is licked.”

Dr. Gordon has advanced training in intracranial and spinal neurosurgical techniques for the correction of intervertebral disc disease, cervical vertebral instability, spinal cord trauma/fracture, Chiari malformation and brain tumor resection.
Lorra Garrick has been covering medical, fitness and cybersecurity topics for many years, having written thousands of articles for print magazines and websites, including as a ghostwriter. She’s also a former ACE-certified personal trainer.