Diagnostic challenges of radiation necrosis

Radiation necrosis (RN) may closely mimic tumor progression or recurrence (TPR) in its clinical presentation and imaging findings in brain tumor patients. In this issue, Korchi et al describe imaging appearances of five consecutive cases of RN from 73 skull-based tumors treated with proton-beam radiotherapy (RT) in Switzerland. An important feature of this study is the selection of patients with extra-axial tumors that tend to recur locally. As such, intra-axial lesions detected following RT more likely represent radiation injury rather than TPR - an interesting model to study imaging findings of RN. Their findings are concordant with those seen with photon RT suggesting that the process of RN may be partly independent of underlying pathology and radiation modality. This study, however, does not help us understand how to distinguish these lesions from TPR. (author)