A new test is being developed in human medicine which allows for breast and a type of lung cancer testing with a blood sample.
This exciting development may be a sentinel for testing in pets that is so needed. Dog cancer is now the number one killer of dogs in the US, and early intervention is therefore becoming more and more important.
One of the reasons this is an essential post for dog guardians is not that the test being developed will be used for dogs right now. More importantly, it is because there is a common misconception that one can test for cancer in a dog using a blood test.
I have heard many times the phrase, “The blood work was fine” from people first becoming familiar with dog cancer. Although this is a bit reassuring, when we are dealing with malignant cancers it really is just barely reassuring… to someone in my position at least.
Let me explain.
First of all, one cannot diagnose cancer (except possibly some leukemias) with a blood test. So a normal result does not rule out cancer or mean that we don’t have spread.
Second, folks need to understand that these blood tests we have are very coarse measuring instruments. Take the kidney markers, as one example. These markers will not go up until 2/3 of the kidney tissue is not working normally. That’s a huge amount! So we can literally have half the kidney volume not working in a dog and have normal kidney markers. Other testing gives us more accurate and complete information.
Third, we need to understand that there is an issue called micrometastasis, which you can learn more about here.
The best way to tell if there are cancer cells in an area is to sample the area and send the sample to a pathology lab. The pathologist will send a report on the sample which will describe whether it contains cancer cells or not.
There are different types of samples that can be submitted. A biopsy is a piece of the tissue (or the whole lump, for that matter). Sometimes a fine needle aspirate is used to collect cells, which is where a needle is used to suck out cells for submission to the lab. Sometimes other body fluids can be used that are collected from body cavities or organs too.
There is a commercial veterinary test for lymphoma that can be used on the blood, yet the manufacturers caution against relying on the test results to rule in or rule out the disease definitively. There is also a urine test that can be used for bladder cancer, although the interpretation can be tricky (if it’s negative, there is likely no cancer. If it’s positive, we don’t know).
So, we are left in some cases with a rather unhappy situation that I describe as an “information deficiency state”. This is a fancy way of saying we sometimes have to guess as to the best possible medical step in the absence of cold, hard facts. In these cases, we rely on experience, judgment, and treatment plan analysis…and intuition.
If you would like more information, check out the Guide.
Dr. Demian Dressler is internationally recognized as “the dog cancer vet” because of his innovations in the field of dog cancer management, and the popularity of his blog here at Dog Cancer Blog. The owner of South Shore Veterinary Care, a full-service veterinary hospital in Maui, Hawaii, Dr. Dressler studied Animal Physiology and received a Bachelor of Science degree from the University of California at Davis before earning his Doctorate in Veterinary Medicine from Cornell University. After practicing at Killewald Animal Hospital in Amherst, New York, he returned to his home state, Hawaii, to practice at the East Honolulu Pet Hospital before heading home to Maui to open his own hospital. Dr. Dressler consults both dog lovers and veterinary professionals, and is sought after as a speaker on topics ranging from the links between lifestyle choices and disease, nutrition and cancer, and animal ethics. His television appearances include “Ask the Vet” segments on local news programs. He is the author of The Dog Cancer Survival Guide: Full Spectrum Treatments to Optimize Your Dog’s Life Quality and Longevity. He is a member of the American Veterinary Medical Association, the Hawaii Veterinary Medical Association, the American Association of Avian Veterinarians, the National Animal Supplement Council and CORE (Comparative Orthopedic Research Evaluation). He is also an advisory board member for Pacific Primate Sanctuary.