Magnetic resonance imaging will be helpful to pick out a genetic mutation in a brain tumor. According to Donald O’Rourke, M.D., of the University of Pennsylvania, in glioblastoma multiforme, changes in regional cerebral blood volume picked up by MR perfusion-weighted imaging can indicate that the tumor carries a particularly aggressive oncogene. It was noted in specific that variant III of the epidermal growth factor receptor (EGFR) might be associated with changes in regional cerebral blood volume that could be distinguished from those caused by other forms of the oncogene. The so-called EGFRvIII mutation occurs in about 35% of glioblastomas and is associated with poorer survival. It up-regulates vascular endothelial growth factor (VEGF), a pro-angiogenic factor. The researchers tested tissue samples from 35 patients with glioblastoma. Dr. O’Rourke said that they then tracked blood volume changes in routine MRIs taken to follow the tumors. Interestingly, the increase in blood volume was not completely explained by the effects of EGFRvIII on VEGF, he said, possibly because the oncogene affects other pro-angiogenic factors. Nonetheless, the model developed by the researchers using blood volume to predict EGFRvIII status was highly predictive and even better when blood volume and VEGF were combined, Dr. O’Rourke said. Specifically, every unit increase in regional cerebral blood volume more than doubled the odds that the tumor had EGFRvIII. The odds ratio was 2.49, with a 95% confidence interval from 1.12 to 5.56, which was significant at P=0.026. In the model with blood volume and VEGF combined, the odds ratio was 2.7, with a 95% confidence interval from 1.04 to 6.99, which was significant at P=0.041.