Veterinary Oncology Falsehoods and Fallacies: Part II
Veterinary Oncology Falsehoods and Fallacies: Part 2
Kimberly Reeds, DVM, MS, DACVIM (oncology)
Once people discover that I am a veterinary oncologist, the next statement is usually “I didn’t know that you could treat cancer in pets! What do you use, like chemotherapy and stuff?” The answer is yes. Yes, we do chemotherapy and other stuff.
Fallacy #5 – Cancer in pets isn’t treatable.
Clearly this one is wrong, or I wouldn’t have a job. Cancer in pets is often very treatable, and many of the treatment options available for humans are also available for our pets. Even if we are in the rare situation that no treatment options are available for the pet’s cancer, we still have options pertaining to increasing the pet’s quality of life. There’s always something that can be done.
There are three main treatment options available for cancer. Which treatment is best depends on what the cancer is and how far it has spread. Once a mass is found, it needs to be sampled. There are a few different ways for this to be accomplished, sometimes with a needle sample, sometimes with a biopsy, and sometimes with removal of a tumor.
Once we know what the mass is, we will be able to look at the common places that the cancer prefers to spread. We will perform staging diagnostics to look for these areas of spread, or metastasis. These diagnostics may include x-rays, ultrasound exams, or advanced imaging with CT or MRI scans.
Once we know what it is, and where it has/has not spread to, we then know what the best plan of attack is. For many tumors, surgery is the first line of defense. This will remove the tumor in its entirety in some cases, while in others it will decrease the burden of the cancer on the body. The best outcomes in pets with cancer often occur when there is a tumor of the skin, that has not spread to other areas of the body, that can be completely removed with surgery. For any tumors, this may be the only treatment recommended!
If treatment beyond surgery is needed, or if the cancer is not able to be removed, chemotherapy and/or radiation therapy are available. Medical oncologists, such as myself, focus more on the chemotherapy treatment of cancer while radiation oncologists focus on radiation therapy.
Fallacy #6 – Even though it is treatable, the treatments make the pet very sick.
The experience of a pet receiving cancer treatment is often drastically different than a human receiving cancer treatment. While we do our best to put the cancer in remission and increase how long the pet lives, our main focus is maintaining, or achieving, a good to excellent quality of life.
When pets receive chemotherapy, they are of course going to experience some side effects, but in most cases, the side effects are mild and go away without treatment. We expect less than 5% of chemotherapy patients to have significant side effects that are severe enough to require hospitalization.
With any chemotherapy drug, the main side effects that are expected are bone marrow suppression, alopecia, and gastrointestinal upset. The risk with bone marrow suppression is lowering of cell counts, most importantly the white blood cells and platelets. There are many white blood cells in the blood, with the most important one in chemotherapy patients being the neutrophil. This is the main cell that helps the body fight infection, and if they become too low, the patient is at risk for a serious infection called sepsis. Sepsis occurs when bacteria are able to enter the blood stream. The most common source of these bacteria is the normal bacteria that are present in the intestines, but infections in other parts of the body, including the bladder, lungs, and skin, can also enter the blood. Monitoring of cell counts with a complete blood count (aka CBC) is crucial for patients receiving chemotherapy. This allows me to adjust the patient’s treatment by including antibiotics, delaying chemotherapy, or lowering the next dose of chemotherapy. The other cell that is important to monitor in chemotherapy patients is the platelet. Platelets are vital to proper blood clotting, and if they become too low, the patient is at risk for bleeding problems. The platelet count is also included in the CBC.
Alopecia is actually quite rare in dogs and cats. There are certain dog breeds that are at risk for this side effect including poodles, the Bichon Frise, and Old English Sheepdogs. Many patients will lose their whiskers and eyelashes, and any area that is shaved, such as the area on the leg for a catheter placement, will grow back more slowly.
The risk and timing of gastrointestinal (stomach and intestines) upset varies with the drug administered. With some drugs, vomiting occurs immediately after the drug is given; however, it is more common for the patient to experience vomiting, anorexia, and possibly diarrhea 3-5 days after chemotherapy has been administered. For most patients, these symptoms are mild and go away with no treatment. For others, these symptoms can be severe and require hospitalization for fluid therapy, antibiotics, and anti-vomiting medications.
Overall, my chemotherapy patients handle their treatments very well, and many owners, and pets, are pleased with the quality of life that they are able to achieve. If at some point the patient’s quality of life isn’t what we want it to be, we always have the option of trying a lower dose of the drug, trying a completely different drug, or stopping chemotherapy completely.
I hope that I have cleared up some of the confusion surrounding the diagnosis and treatment of pets with cancer. I would like to leave you with one last thought: if you are having a tumor removed from your pet, please, please, have your veterinarian submit a sample to a lab for evaluation. If I don’t know what the diagnosis is, there is no way for me to determine what options are available for treatment.