Currently, the only definitive method for telling the difference between side effects of radiation therapy for brain tumors and tumor recurrence involves a biopsy of the brain tissue, said Dr. Ewell, an assistant professor in the department of radiation oncology at the University of Arizona in Tucson. MRS has the potential to eliminate the need for this invasive procedure. The authors retrospectively studied 33 brain tumor patients that had MRS spectra taken during the course of their treatment. Choline (Cho) is a metabolite that is elevate
The authors used the ratio of Cho/NAA to predict whether a lesion represented radiation necrosis or recurrent tumor: A high ratio would indicate tumor, whereas a low ratio would indicate radiation necrosis. This metabolite ratio was successful in determining the difference in roughly 80% of the cases.
They then developed a model that would indicate which of three different clinical decisions are indicated based on the ratio: If this ratio is ≤1.1, the patient would have routine follow-up.