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GEN News Highlights : Jul 23, 2013

Detecting, Tracking Brain Tumors with Digital PCR

Diagnosing a brain tumor often involves invasive neurosurgery. Being able to detect and monitor brain tumors without a biopsy would be a boon for clinicians, and could help them catch—and treat—malignant neoplasms sooner.

Researchers at Massachusetts General Hospital (MGH) and their colleagues present in Molecular Therapy–Nucleic Acids today a digital PCR-based approach for the detection of a tumor-associated IDH1 mutation in patient cerebrospinal fluid (CSF) samples.

“Knowing the IDH1 mutation status of these tumors could help guide treatment decisions, since a number of companies are developing drugs that specifically target that mutant enzyme,” explained MGH’s Xandra Breakefield, Ph.D.

Added Fred Hochberg, M.D.: “The current approach for patients who may have a brain tumor is first to have a brain scan and then a biopsy to determine whether a growth is malignant. Patients may have a second operation to remove the tumor prior to beginning radiation therapy and chemotherapy, but none of these treatments are targeted to the specific molecular nature of the tumor.”

Dr. Hochberg noted that a molecular diagnostic assay to detect tumor-associated mutations in CSF could help physicians begin treating patients who show them sooner. Such an assay, like the PCR-based test he and his colleagues present, “would allow us to immediately initiate treatment that is personalized for that patient without the need for surgical biopsy,” Dr. Hochberg said in a statement. “For some patients, the treatment could shrink a tumor before surgical removal, for others it may control tumor growth to the point that surgery is not necessary, which in addition to keeping patients from undergoing an unnecessary procedure, could save costs.”

Writing in Molecular Therapy–Nucleic Acids, Drs. Breakefield and Hochberg et al. show that their digital PCR-based approach accurately detected the presence and abundance of mutant IDH1 in the CSF of five of the eight patients they studied who were known to have IDH1-mutant tumors. Of the remaining three, two patients who showed false-negative results had low-grade tumors. The last patient had a smaller tumor than the rest. More work is needed, the researchers say, to determine whether tumor grade and size affect their ability to detect mutations.

Still, the researchers are hopeful their findings could translate into meaningful results in the clinic. Going forward, Dr. Breakefield said, “Reliable detection of tumor-associated mutations in cerebrospinal fluid with digital PCR would provide a biomarker for monitoring and tracking tumors without invasive neurosurgery.”