The two most common brain tumors in dogs and cats are gliomas (astrocytomas and oligodendrogliomas) and meningiomas. Although these are the most common tumors that arise from the brain, other tumors types can spread to the brain from distant sites, including breast (mammary), prostate, and lung carcinomas and hemangiosarcomas.
Some dog breeds appear to be at increased risk of developing brain tumors. For example, flat-nosed breeds, such as Boxers, Boston Terriers, Pugs, etc are at an increased risk for gliomas whereas long-nosed dog breeds are at increased risk of meningiomas. Dog breeds at particularly increased risk include the Boxer, Golden Retriever, Doberman Pinscher, Scottish Terrier, and Old English Sheepdog. Mengiomas are the most common brain tumor in cats and male cats appear to be at a higher risk than female cats.
The cause of brain tumors in dogs and cats is unknown although dietary, environmental, genetic, chemical, viral, traumatic and immunologic factors may be possible considerations.
In general, primary brain tumors are thought to be slow growing. Because of their slow growth, the brain can compensate well. However, as the tumor is growing there can be vague signs. More obvious signs are seen suddenly only after the tumor has gotten so large that the brain can no longer compensate. For humans, often the initial sign is a severe and persistent headache, which may show as hiding more during the day or less play or purring. For dogs and cats, often the first obvious sign is a seizure.
Brain tumors are diagnosed with advanced imaging with an MRI and sometimes with a CT-scan, which are both available at WVRC. Because a low plane of anesthesia is required for the MRI, pre-anesthetic diagnostics are indicated such as chest x-rays to evaluation the lungs and heart and a pre-anesthetic blood work (CBC and chemistry profile). Depending on your pet’s signs, additional diagnostics may be discussed by your veterinarian. After the MRI often a small sample of cerebrospinal fluid (CSF) is evaluated.
Although features on an MRI have greatly helped our ability to distinguish brain lesions, the mainstay of diagnosis is still a biopsy. For practical reasons, biopsy is not always recommended.
Treatment and Prognosis:
The major goals of therapy include improvement of clinical signs (palliation) and to eradicate the tumor or reduce its size.
Treatment options for this cancer include:
1. Palliation – We use prednisone +/- anti-seizure medications to decrease swelling associated with the tumor and to raise the seizure threshold, making it less likely that the pet will seizure. Because palliative therapy does not kill or slow down the cancer cells, it is likely that this tumor will continue to grow and eventually your pet will experience seizures again. The average survival time for dogs with meningiomas undergoing palliative therapy is 3-6 months.
2. Radiation Therapy – With this treatment, a beam of energy is directed at the tumor to kill or slow down the cancer cells. The average survival time for pets with meningiomas undergoing radiation therapy is 1-1.5 years. Radiation therapy is often performed in conjunction with palliative treatments. Because we do not offer radiation therapy at WVRC, we would need to refer you to another facility.
3. Chemotherapy – Certain chemotherapeutics have efficacy in treating dogs with this disease. Chemotherapy is administered with the primary goal of fighting cancer while maintaining a very good quality of life for the pet. Our drugs are dosed with this goal in mind. However, side effects are possible when using chemotherapy and it is difficult to predict which pets may be more sensitive to our drugs than others. Please see the provided chemotherapy handout for more information about the possible chemotherapy side effects. Unfortunately, little data exists which would predict the response rate or response duration for dogs with brain cancer undergoing chemotherapy treatment. Therefore, I am unable to provide an average survival time.