Brain tumors affect roughly 14.5 out of every 100,000 dogs, making them relatively uncommon but far from rare. They account for about 2 to 5% of all cancers diagnosed in dogs. Post-mortem studies find intracranial tumors in 2 to 4.5% of all dogs examined, which suggests many cases go undetected during a dog’s life.
Which Dogs Are Most at Risk
Brain tumors overwhelmingly affect older dogs. The median age at diagnosis is 9 years, and 95% of dogs with brain tumors are 5 or older at the time they’re found. Cases in dogs younger than 5 are uncommon.
Certain breeds face significantly higher risk. English Bulldogs, French Bulldogs, and Boxers are especially prone to primary brain tumors, particularly a type called glioma that grows from the brain’s supportive tissue. Flat-faced (brachycephalic) breeds in general tend to develop gliomas at higher rates, while longer-nosed breeds are more likely to develop meningiomas, tumors that grow from the membranes surrounding the brain. Golden Retrievers, Labrador Retrievers, and other large breeds also appear more frequently in brain tumor cases.
The Most Common Tumor Types
Meningioma is the single most common primary brain tumor in dogs (and in cats and humans, for that matter). These tumors grow on the outer coverings of the brain rather than within the brain tissue itself, which sometimes makes them easier to treat surgically. In one large study, meningiomas accounted for 46% of all brain tumor cases.
Gliomas are the second major category. These grow within the brain tissue and tend to be more difficult to access and remove. They’re the tumor type most associated with brachycephalic breeds like Boxers and Bulldogs. Choroid plexus tumors, which develop in the fluid-producing structures inside the brain, are less common but round out the three main types veterinarians encounter.
It’s also worth knowing that not all brain tumors originate in the brain. Secondary tumors, meaning cancers that started elsewhere in the body and spread to the brain, also occur. Primary tumors that start in the brain are the more commonly studied and discussed category in veterinary neurology.
Seizures Are the Leading Warning Sign
Seizures are the most common reason a brain tumor gets discovered. In a study of 97 dogs with confirmed brain tumors, 45% had seizures as their initial clinical sign. The link between seizures and tumors gets stronger with age: seizures were reported in 32% of dogs 8 years old and younger, but in 65% of dogs older than 8. Veterinary neurologists generally recommend investigating for a brain tumor whenever a dog has its first seizure after age 4.
Other signs include circling (walking in repetitive circles), loss of coordination, head tilting, changes in behavior or personality, vision problems, and general disorientation. These symptoms develop because the growing tumor puts pressure on surrounding brain structures. The specific signs depend on where in the brain the tumor is located. A tumor near the front of the brain might cause personality changes and seizures, while one near the back might affect balance and coordination.
How Brain Tumors Are Found
MRI is the standard tool for detecting brain tumors in dogs. It provides detailed images of soft tissue that CT scans and X-rays can’t match for the brain. The catch is that MRI requires general anesthesia in dogs, since they can’t hold still for the 30 to 60 minutes the scan takes. This adds cost and a small amount of risk, particularly for older dogs. A definitive diagnosis technically requires a tissue biopsy, but in many cases veterinarians make a presumptive diagnosis based on the MRI appearance, the dog’s breed, and the tumor’s location.
What Treatment Looks Like
Treatment options and outcomes vary dramatically depending on the tumor type. For meningiomas, a 2025 study comparing surgery and radiation therapy in 285 dogs found that radiation therapy produced a median survival of about 696 days (roughly 23 months), while surgery resulted in a median survival of about 297 days (roughly 10 months). When researchers used statistical modeling to account for differences between the two groups, the gap narrowed but radiation still came out ahead: an estimated 673 days for radiation versus 480 days for surgery.
Gliomas carry a tougher prognosis. Dogs that received definitive treatment (surgery, radiation, or both) survived a median of 84 days, compared to just 26 days with palliative care alone. That’s a meaningful improvement, but the overall outlook remains poor compared to meningiomas.
Radiation protocols have become more refined in recent years. Conventional treatment involves 18 to 20 sessions delivered over several weeks and produces median survival times of 16 to 18 months. Newer approaches that use fewer, higher-dose sessions (sometimes as few as 3 to 10 treatments) appear to achieve similar results while reducing the number of times a dog needs anesthesia. For dogs managed with only anti-seizure medications and steroids to reduce brain swelling, survival is significantly shorter, though this approach can still improve quality of life for dogs that aren’t candidates for more aggressive treatment.
Medical management without surgery or radiation remains the reality for many families, whether due to cost (MRI and radiation can run into thousands of dollars), the dog’s age and overall health, or tumor location. The focus in those cases shifts to controlling symptoms and maintaining comfort for as long as possible.
Putting the Numbers in Perspective
At 14.5 cases per 100,000 dogs, brain tumors are far less common than skin tumors, lymphoma, or mast cell tumors. The most frequently diagnosed tumor in dogs overall is a benign skin growth called a cutaneous histiocytoma, which occurs at a rate of 337 per 100,000 dogs per year, more than 20 times the rate of brain tumors. But because brain tumors produce serious neurological symptoms and carry a guarded prognosis, they loom larger in pet owners’ minds than their numbers might suggest.
If your dog is a younger adult with no neurological symptoms, the odds of a brain tumor are very low. If your dog is older than 5, belongs to a predisposed breed, and has started having seizures or showing unusual neurological behavior, the probability rises enough that imaging is worth discussing with your veterinarian.