Two Dogs: Same Cancer Diagnosis, Two Different Outcomes

Published Nov. 11, 2015

Most owners of pets with cancer are fixated on the familiar phrase “survival time.” The words describe the approximate length of time a pet is expected to live following its diagnosis.

Survival time is a meaningful endpoint to measure for humans with cancer, where death occurs as a natural part of disease progression. In veterinary medicine, survival time is a complicated marker of outcome because of the bias introduced by euthanasia.

I struggle with answering owners when they ask me to predict their pet’s survival time. Despite being an expert in veterinary oncology, trying to anticipate how long a patient will live is nearly impossible.

Experience affords me the ability to describe the signs their pet will show as the disease progresses. I can forecast whether there will be issues related to appetite or pain, respiratory or gastrointestinal distress. I can usually pinpoint how long a decline will last on the order of days to weeks to months. But I cannot tell an owner how long their pet will live because that decision, in the vast majority of cases I see, is up to them.

Consider the hypothetical scenario of two different sets of owners of dogs with an identical diagnosis of lymphoma. Lymphoma is a common blood borne cancer in dogs and cats.

Dog #1, a 5-year-old mixed breed, was diagnosed after his primary veterinarian palpated enlarged lymph nodes during its physical exam performed prior to routine vaccinations. Lymphoma is frequently diagnosed incidentally, as was seen in this dog that showed no adverse signs related to its cancer.

Dog #2, a 14-year-old shepherd, was determined to have lymphoma after his primary veterinarian performed a thorough diagnostic work up for a several week history of lethargy, vomiting, poor appetite, and weight loss.

Both dogs were diagnosed with the same cancer. Both owners underwent the same consultation with me and I made the exact same diagnostic and treatment recommendations in each case.

The statistics and data I memorized in order to become a board certified medical oncologist tells me that without treatment, dogs diagnosed with lymphoma live an average of one month. With treatment, survival time is about 12 months. This information was relayed to both owners, including expected quality of life, both with and without treatment.

Dog #1’s owners elected to pursue treatment. They felt their pet was young, otherwise healthy, and they possessed the emotional and financial reserves to move forward with all of my recommendations. Their pet underwent six months of treatment, attaining remission for a total of 14 months, and was euthanized when the cancer resurfaced and clinical signs caused a decline in quality of life unacceptable to their standards.

Dog #2’s owners elected to euthanize their dog the day after meeting with me. They knew their pet was geriatric and approaching the end of his normal expected lifespan. Their dog was also sick at the time of diagnosis, further reducing their interest in pursuing aggressive treatment.

In each instance above, despite the identical diagnosis, the survival times are vastly different—1 day versus 20 months.

These examples demonstrate several key points:

Despite what research studies suggest, neither dog lived to their expected survival. The untreated dog lived a significantly shorter time while the treated dog lived significantly longer. My predictions for survival time were incorrect in both cases

In both cases, the owners decided their pets’ survival time. Neither dog passed “naturally,” so we will never know an accurate numerical time frame for how long they would have survived.

Variables such as age, overall health status, finances, etc. always play a role in how long pets with cancer will survive. These are unpredictable influences that change outcome equally as often as the more controllable variables do.

I understand why survival time is a major consideration point for owners of pets with cancer. But I also understand my limitations in anticipating survival for the majority of animals I meet.

Owners are often frustrated when I’m vague in my description of how long I believe their pet will live. Many are disappointed the information cannot be measured in more absolute terms.

The best I can do is honestly and openly guide owners through their journey with a pet with cancer and guide them toward the endpoints I consider essential in making decisions about life, death, treatment, palliative care, and quality of life.

Even if the journey is only a few hours long, my job is to ensure that time truly is the most sacred part of the phrase “survival time.”