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Taking a smart approach to brain cancer

By Kelley Weir

novel tool may improve diagnosis and treatment of tumors

When Dr. Annie Chen-Allen first saw Jade, an 11-year-old Pit Bull cross, the usually happy dog had been having seizures. The diagnosis was a lesion in her brain. The important question, though, was what kind?

A lesion is any area of the brain that has been damaged due to infiltration of abnormal cells. It sounds simple, but treating brain lesions can be complicated because there are many types. Lesions can range from small to large, from few to many, or from relatively harmless to life threatening.

In some cases, the lesion could be a brain tumor. These tumors are not uncommon in older dogs. Adult dogs of several related short-nose breeds, such as Boxers, English Bulldogs and Boston Terriers, are often cited as having the highest incidence of brain tumors among domestic animals. A recent study indicated that Golden Retrievers also have a high incidence.

Brain tumors vary widely in their level of malignancy. Some can be treated quite effectively—if the veterinarian can identify the exact type.

getting a definitive diagnosis

As with many diseases, a biopsy is the only definitive way to diagnose a tumor and determine what treatments are possible. Until recently, performing a biopsy required brain surgery, which has the potential to cause postoperative complications. Jade’s owners had brought their dog to the right place, Washington State University, where Dr. Chen-Allen is working on a Morris Animal Foundation–funded study to evaluate a promising, less invasive brain-biopsy procedure for dogs.

“In veterinary medicine, definitive brain tumor diagnosis is often made postmortem,” Dr. Chen-Allen says. “Although the advent of magnetic resonance imaging (MRI) has increased the sophistication for detection and characterization of lesions in the brain, tumor diagnosis is only presumptive with imaging.”

She is testing an MRI-guided frameless stereotactic brain-biopsy system, a fairly new method that takes a sample the size of a grain of rice from a brain tumor using a neuronavigation system. The stereotactic system uses three-dimensional coordinates from a previous MRI to locate the tumor.

Conventional stereotactic systems required a metal frame to be attached to a patient to acquire images, which can be complicated, but the frameless technique does not. This novel procedure shows potential to be superior to open brain biopsies because it allows a surgeon access to places a scalpel cannot reach and to access the brain without damaging surrounding tissue. The procedure is done in real time so that the clinician knows exactly where and how far to advance the needle.

“A clinically applicable stereotactic brain-biopsy system that can improve brain lesion diagnosis is greatly needed in veterinary medicine,” Dr. Chen-Allen says. “A neuropathological diagnosis is critical for implementation of appropriate therapy.”

moving on to treatment

The options for treating brain tumors include radiation therapy, chemotherapy and palliative treatment. But brain tumors present unique problems related to their location and the tissues they affect. Dr. Chen-Allen’s study shows that frameless stereotactic biopsy of lesions is a valuable and safe tool for diagnosing brain lesions, regardless of lesion location.

Potential risks of this type of biopsy, like bleeding at the area of surgery, are the same as those reported with the conventional biopsy technique. Patients are usually kept in intensive care for 24 hours after the procedure, allowing clinicians to administer supportive care, monitor vital signs and detect any signs of neurologic deterioration. Patients are usually discharged 48 to 72 hours after the biopsy.

“The clients that have enrolled in this study have all been very thankful to the Foundation for providing the financial support for this clinical trial,” Dr. Chen-Allen says. “Although there are always risks associated with procedures like these, owners are comforted knowing that they are able to provide their pets with the most advanced medicine available.”

So far, five dogs have successfully undergone the advanced biopsy technique and follow-up treatment. Within days of Jade’s biopsy, Dr. Chen-Allen and her team knew the type of tumor she had and, knowing that Jade’s type of tumor responds well to radiation therapy, the team prescribed 18 treatments. Luckily, Jade responded well and was able to add precious months to her life at home with her family.

Categories: Animal health, Canine health, Dog health
May 13, 2011