'Why Do Different Doctors Treat Pet Cancer Differently?' and Other Questions Answered

Published Feb. 5, 2015

In matters of pets and cancer, there are certain questions I encounter more frequently than others. Despite the myriad of diagnoses and their associated treatment options I am tasked with explaining, troubled owners have more typical concerns: How did my pet get cancer? Will he or she become sick from treatment? What is my pet’s prognosis?

Less common questions arise and are equally as important to address, mainly because they tend to surface after owners have already committed to a treatment plan. Assuaging an owner’s concerns once a pet has started receiving chemotherapy can be tricky at best, and near impossible at worst.

Here are some examples of the less routine questions I face:

1. "Why do different oncologists have different protocols/cutoff blood counts for treatments, or administer treatments differently?"

Owners are surprised to hear different recommendations from different oncologists. I’ve encountered this when owners see me after their pet has started treatment elsewhere and are continuing care with me, or after they’ve done some research and discovered protocols online or via other doctors. The expectation is that there’s a “precise” way to treat a particular cancer. However, this tends to be a major oversimplification for most of my patients.

Even for cancers considered to have a true “gold standard” of care, often the nuances of the protocols are slightly different for each attending doctor. Typically this varies with their training, personal experience, and familiarity with the disease in question.

I use the analogy of baking chocolate chip cookies. Everyone has their favorite recipe for doing so, but the outcome is typically the same as long as the major ingredients are kept equal.

2. "Can my dog/cat with cancer still receive vaccines and flea-tick/heartworm medication?"

I would consider this a “hot button” topic in veterinary oncology, meaning it’s one that is likely to evoke considerable emotion and opinion but lacks factual information to support an actual “correct” answer.

Other than injection site sarcomas in cats, no information exists to support the concept that vaccinations lead to cancer in pets. Yet, some oncologists do not advocate vaccinating their patients, while others are fine with doing so.

We know that dogs undergoing treatment with chemotherapy can mount adequate immune responses to vaccination, which supports the notion that their immune systems function adequately in the face of anti-cancer treatment.

What we don’t know is if the physical act of vaccination could result in some sort of stimulation of the immune system that could contribute to cancer progression or relapse of disease, or a patient becoming refractory to a previously successful treatment.

People with a history of cancer are instructed to receive influenza vaccines, not because they are more prone to developing the flu, but because they are more likely to develop complications resulting from infection. Other than this, veterinary oncologists have surprisingly little data from our human counterparts to help base our recommendations on.

I answer this question on a case-by-case basis with owners and discuss the pros and cons of vaccinating versus not vaccinating. It’s a decision we reach together in a truly holistic fashion, where concerns for the pet’s safety and the family members' safety are considered together.

3. "Isn’t there a treatment for my pet’s cancer that comes in a pill form? I’ve heard oral chemotherapy is less toxic and less likely to cause side effects in my cat/dog."

The vast majority of cytotoxic chemotherapy prescribed in veterinary patients is administered intravenously (IV). There are a few oral cytotoxic treatments available, but these forms are not considered any less toxic than their IV counterparts. In fact, the chemotherapy drug most likely to cause a lowered white blood cell count in dogs is an oral medication called CCNU (aka Lomustine).

The idea that oral chemotherapy is less noxious for a pet is false. Any chemotherapy has the potential for adverse effects. The good news is, when prescribed correctly, the risk is absolutely minimal.

4. "My dog/cat was recently diagnosed with cancer, but he/she is not acting sick. Isn’t it better to wait to start treatment until they are showing signs of their disease?"

I hear this question most frequently from owners of dogs with lymphoma, as many of those patients are diagnosed incidentally. Unfortunately, waiting to treat any pet with cancer until they are manifesting outward signs usually means a poorer outcome.

Pets who are self-sufficient, meaning they are eating well and not having vomiting, diarrhea, weight loss, breathing difficulties, or other adverse clinical signs, tend to have a better response to treatment and are also less likely to experience side effects. Therefore, the most ideal time to institute therapy is immediately following a diagnosis.

5. "Why do you draw blood samples from neck veins?"

For most pets with cancer, and nearly all pets undergoing chemotherapy treatments, routine blood samples are drawn from the jugular vein. This is a large vein located on either side of the neck, which drains blood from the head region.

Although it sounds somewhat barbaric, obtaining blood samples from the jugular vein is a common procedure in veterinary patients. Oncologists prefer to reserve smaller, more peripherally located veins along the limbs for the administration of injectable chemotherapy. Therefore, every attempt is made to reserve the integrity of these veins for administration of treatments and to avoid excessive scarring.

I hope this is useful information for anyone researching his or her pet’s diagnosis and trying to make decisions about their care. As always, I urge you to seek consultation with a board certified veterinary oncologist in order to obtain the most up to date information as well as to establish the most appropriate treatment plan for your pet.

Visit these sites to find a board certified veterinary oncologist near you:

Veterinary Cancer Society

American College of Veterinary Internal Medicine