Response assessment in neuro-oncology.

Accuracy and reproducibility in determining response to therapy and tumor progression can be difficult to achieve for nervous system tumors. Current response criteria vary depending on the pathology and have several limitations. Until recently, the most widely used criteria for gliomas were "Macdonald criteria," based on two-dimensional tumor measurements on neuroimaging studies. However, the Response Assessment in Neuro-Oncology (RANO) Working Group has published new recommendations in high-grade gliomas and is working on recommendations for other nervous system tumors. This article reviews current response criteria for high-grade glioma, low-grade glioma, brain metastasis, meningioma, and schwannoma.