It's not a tumor! (but it really is)
If you haven’t read Dr. Holland’s blog post from last week (link to There’s a whole lot of shakin’ goin on!) go do it now! It is imperative that you have read that information prior to reading today’s post.
Arnold Schwarzenegger starred as Detective John Kimble in Kindergarten Cop (1990). One of the best lines of the movie is when he is complaining of a headache, and one of his students says that it might be a tumor. His response is “It’s not a tumor! It’s not a tumor at all!”
Sometimes it really is a tumor. In both people and pets, the symptoms caused by a brain tumor vary based on how many tumors are present, how big the tumor(s) are, where the tumor(s) are located, and the rate of growth. In people, common symptoms that can indicate the presence of a brain tumor include headaches, nausea or vomiting, vision disturbances, balance issues, confusion, personality or behavior changes, and seizures. Unfortunately, our pets cannot tell us that they have a headache, or that their world is spinning, so we have to rely on the more obvious indicators. The more common symptoms exhibited by pets with brain tumors include personality/behavior changes, which is more common in cats, and seizures, which are more common in dogs.
As with most cancers, brain tumors tend to occur in older pets. Dogs develop a wider variety of brain tumors, and develop brain tumors more often than cats. The majority of brain tumors in pets are classified as primary brain tumors, meaning that they originate from the brain tissue rather than having spread, or metastasized, to the brain. Meningiomas are the most common primary tumors of the brain in both dogs and cats. These arise from the membranes that cover the brain and spinal cord. Secondary tumors include those that have spread, or metastasized, to the brain or those that affect the brain by local extension. There are many secondary tumors that may affect the brain including nasal tumors, skull tumors, pituitary tumors, hemangiosarcoma, and lymphoma.
The symptoms exhibited by pets with brain tumors can also be present with other disease processes, making a complete medical workup necessary. As many of these pets are older, it is also important to know if there are any other concurrent medical problems so that appropriate diagnostic and treatment recommendations, as well as the overall prognosis of the pet, can be discussed. Blood work consisting of a complete blood count and chemistry profile should be examined. These results can reveal signs of an infection or inflammation that may be causing or contributing to the pet’s symptoms. Metabolic disturbances that can cause seizures or other neurologic dysfunction such as liver failure, changes in electrolytes, or severe kidney disease, may also be detected. While there are biomarkers, or indicators, of specific brain tumors that can be detected on tumor samples or in the blood or urine of people, these are not available for our pets.
Either computed tomography (CT) or magnetic resonance imaging (MRI) is required to diagnose the presence of a brain tumor. Overall, an MRI will provide a better, more in-depth look at the brain than a CT, and is the preferred test for diagnosing a brain tumor; however, a CT scan will also diagnose the majority of brain tumors. A CT scan can also be used to examinet the chest and abdomen for areas of tumor spread or origination. When either of these tests are performed, a radiologist will evaluate the images and provide a suspected diagnosis based on what the tumor looks like and where it is located. A definitive diagnosis of a brain tumor, just as with any tumor in any other location of the body, requires that a biopsy of the tumor be submitted for evaluation. This is not often done in pets as these are risky procedures to perform and there are not many veterinarians that possess the training and skill to perform these tests.
As for treatment of brain tumors, surgery, radiation, and/or chemotherapy may be utilized. Surgical removal of a tumor not only provides tissue for a biopsy and diagnosis, but it may also provide immediate relief of brain compression caused by the tumor. Surgery is considered the treatment of choice for cats with meningiomas, as these tumors tend to be located in areas that are more easily accessible and they also tend to peel away from the normal tissue well.
As many brain tumors occur in locations that aren’t easy to get to, radiation therapy (RT) tends to be recommended more often than surgery, and in some cases, it may be used with surgery. A combination of surgery and RT is more often recommended for dogs with meningiomas than surgery alone. We have already discussed RT in greater detail here (link). While data on the efficacy of intensity modulated radiation therapy or stereotactic radiation therapy is limited in pets, there are many studies that report the outcomes of the use of traditional RT for dog and cat brain tumors.
Unfortunately, there are very few studies investigating the use and efficacy of chemotherapy as a stand-alone treatment in pets with brain tumors; however, chemotherapy is sometimes recommended. Chemotherapy will be included in the treatment plan for any patient with spread of their tumor, whether it be to the brain from some other part of the body or to some other part of the body from the brain. Drugs that have been studied in pets with brain tumors include lomustine, carmustine, and hydroxyurea. Other drugs, such as anti-seizure medications or steroids are often prescribed to help treat the symptoms that the brain tumor is causing.
If you think that your pet is exhibiting symptoms of a brain tumor, have them examined by your primary care veterinarian as soon as possible. Your veterinarian may refer you to HVRH, where we can perform a CT scan to determine if a brain tumor is present. If so, we will be able to discuss the various diagnostic and treatment options that are available. Remember, just as with the majority of cancers in pets, there is usually something that can be done to treat the tumor and/or improve your pet’s quality of life.
