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Advanced Brain Tumor Diagnosis Beyond the Microscope

Breaking Down a Groundbreaking Diagnostic Tool

Every brain tumor is different. An accurate diagnosis is key for figuring out the proper treatment plan.

Genomic DNA methylation profiling is a breakthrough technology that helps physicians diagnose brain tumors more accurately. Like a fingerprint, each tumor's methylation profile is different.

"Methylation profiling is a very powerful diagnostic tool that allows us to more accurately diagnose tumors that are difficult to classify by traditional methods," says Craig M. Horbinski, MD, PhD, director of Neuropathology and professor of Neurological Surgery at Northwestern Medicine. "It's the way of the future: the next big thing in the diagnosis of cancers."

Through the Lou and Jean Malnati Brain Tumor Institute of the Robert H. Lurie Comprehensive Cancer Center of Northwestern University at Northwestern Memorial Hospital, Northwestern Medicine is one of the first in the world to offer methylation profiling to diagnose brain tumors.

A More Accurate Diagnosis

Traditionally, brain tumors have been diagnosed by what pathologists see under the microscope, which is a tissue sample of the brain tumor that was removed during surgery.

"Historically, we were only able to tell if a tumor is low-grade or malignant, what kind of general cancer is present and the grade," says Dr. Horbinski. "With methylation profiling, we can get much more specific, which means we can determine how to treat the cancer with greater accuracy, resulting in better outcomes."

DNA Fingerprints and Origins of Tumors

Each cell in your body has genetic material called DNA. Each cell chemically modifies various parts of its DNA, through a process called methylation. Each kind of cell has a unique pattern of methylation. Thus, every kind of tissue in our bodies — from skin to bowel to lung tissue — can be identified and categorized based on its distinct DNA methylation profile. In the same way, each type of tumor has a unique methylation profile that can tell physicians more about it, including exactly what kind of tumor it is.

Methylation profiling makes it possible to tell the difference between brain tumors that may look similar under the microscope.

Along with the ability to identify the unique DNA profile of tumors, methylation profiling can help physicians understand the origin of a tumor and predict how it may respond to certain therapies. This can lead to a more effective treatment plan.

Better Brain Tumor Treatment Plans

This technology could make the difference between an accurate and an inaccurate diagnosis. According to Dr. Horbinski, methylation profiling adjusts a brain tumor diagnosis in up to a third of patients.

"Methylation profiling is proving to be a game-changer," says Dr. Horbinski. "In many cases, tumors we thought were one thing under the microscope ended up being very different than what we thought. As a result, we've discovered new types of tumors that we didn't even know existed."

Diagnosis drives treatment plans for patients with brain tumors and could drastically improve health outcomes for these patients. With an accurate diagnosis and a better understanding of a tumor's root cause or origin, methylation profiling could also prevent certain patients from undergoing inappropriate treatments or more treatments than they need.

Methylation Profiling in Action

A 4-year-old patient at Ann & Robert H. Lurie Children's Hospital of Chicago was recently referred to Dr. Horbinski. Originally, the patient's care team suspected that the patient may have a grade 3 ependymoma, which is a fast-growing tumor that can form in the brain or spinal cord and is often treated with radiation after surgery. Through methylation profiling, the care team discovered that the patient actually had an astroblastoma, which is a rare glial tumor usually located in the cerebral hemisphere of the brain. It tends to occur in children and typically has good survival rates. As a result, this completely changed the patient care plan, allowing the child to avoid radiation that can be damaging to a developing brain.

Dr. Horbinski predicts that this technology will eventually work for cancers beyond brain tumors, such as leukemia and metastatic cancers of unknown origin. "As time goes on, we envision nearly every cancer being worked up by methylation profiling," he says.

Dr. Horbinski is also director of the Northwestern Nervous System Tumor Bank. Efforts are underway to analyze many of their existing brain tumor tissues, collected before DNA methylation profiling was available. This anonymized data will then be available to Northwestern brain tumor researchers who use those banked cases to better understand brain tumors and develop new treatments.