When a dog has cancer, the two most important factors determining how long they will live and which treatments might help them are (1) what type of cancer they have and (2) has cancer spread to other organs (called metastasis).
We always want to obtain a diagnosis (what type of cancer is present) and find out if metastasis has occurred (has the cancer spread) prior to initiating ANY treatment.
In order to find out if cancer has spread, we perform what we call "staging tests". With these tests, we are looking throughout the body for evidence of cancer, based on where we know that particular type of cancer often travels. The staging tests for a mast cell tumor (skin tumor) are different than for a dog with lymphoma. The staging tests are also different for a young dog versus an older dog and are sometimes even different for a dog that feels sick versus a dog that feels healthy.
When we perform staging tests we are also trying to assess the overall health of the patient. This gives us an idea of which treatments might be reasonable for them in the near future. Do they have a heart murmur? Are their kidneys healthy? Do they have arthritis, which is significantly impacting their quality of life?
In many cases, staging will include full blood work (a complete blood count and a chemistry panel), a urinalysis, 3-view chest x-rays (also called thoracic radiographs) reviewed by a radiologist, and an abdominal ultrasound (performed by a board-certified radiologist or internist). In some cases, staging also includes sampling the lymph node nearest to the tumor.
So why do we feel that these tests are needed prior to surgery and treatment?
You can think of these tests as an insurance policy. You want to know prior to spending money to remove a cancerous skin tumor, that your dog doesn't have cancer anywhere else in his body and that he should have a good prognosis if the surgery goes well.
On more than one occasion, I have seen a family decline to perform an abdominal ultrasound prior to removal of a skin tumor, then the patient dies a month later due to a tumor in the spleen that we didn't know about. If we had performed the ultrasound, we would have found the splenic tumor, recommended removal of the spleen or the family could have chosen not to do any surgery at all. These cases are so sad. If we knew about the tumor in the spleen we never would have recommended surgery for the skin tumor alone. In this type of case, a family spends thousands of dollars for their dog only to live a month - this is what we can avoid with appropriate staging.
Mast cell tumors are very common skin cancers in dogs. Many times these tumors are removed without the vet knowing the diagnosis or doing any staging tests prior to surgery - this is the wrong way to do things. The most important tests to do for a mast cell tumor are (1) aspirate the mass so we know it's a mast cell tumor and (2) aspirate the nearest (draining) lymph node, even if it feels normal. If there are cancer cells in the lymph node, the lymph node should be removed at the same time that the tumor is removed. Removing the tumor and the lymph node gives the dog the best prognosis. If mast cells have spread to a lymph node, these patients still have the chance to live for years, but only if the lymph node is removed and they receive chemotherapy. If the lymph node is not removed and they don't receive chemotherapy, many will only live for 6 months. Talking to an oncologist to discuss all possible options is ideal in this scenario.
The last scenario I will discuss is cancer that has spread to a distant organ such as the lungs or the liver. In many of these cases, surgery will not help the dog live longer or feel better, so we often don't recommend surgery at all. Obviously, every case is different and medicine is never black or white, so there are some exceptions to this rule. However, in general, we do not recommend surgery in these cases. We never want a dog to go through an unnecessary surgery - because of this, staging is a very good investment!
If your dog has cancer and you've decided to treat him palliatively as opposed to treating the cancer itself (palliative treatment = helping a dog feel as good as possible using pain medication and other modalities), then full staging is less important. It is still a good idea to have a diagnosis because there are some types of cancer that will respond to steroids, and in treating with steroids, your dog might feel better and live for a longer period of time.
I appreciate that this is a difficult and confusing topic. An oncologist will understand the behavior of each type of cancer and will know how to appropriately stage a patient prior to treatment. It is always a good idea to get the advice from an oncologist (if possible) if your dog has cancer.
Dr. Lori Cesario
Board Certified Veterinary Oncologist
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