Radiation Necrosis in the Brain: Imaging Features and Differentiation from Tumor Recurrence

Abstract

Radiation necrosis in the brain commonly occurs in three distinct clinical scenarios, namely, radiation therapy for head and neck malignancy or intracranial extraaxial tumor, stereotactic radiation therapy (including radiosurgery) for brain metastasis, and radiation therapy for primary brain tumors. Knowledge of the radiation treatment plan, amount of brain tissue included in the radiation port, type of radiation, location of the primary malignancy, and amount of time elapsed since radiation therapy is extremely important in determining whether the imaging abnormality represents radiation necrosis or recurrent tumor. Conventional magnetic resonance (MR) imaging findings of these two entities overlap considerably, and even at histopathologic analysis, tumor mixed with radiation necrosis is a common finding. Advanced imaging modalities such as diffusion tensor imaging and perfusion MR imaging (with calculation of certain specific parameters such as apparent diffusion coefficient ratios, relative peak height, and percentage of signal recovery), MR spectroscopy, and positron emission tomography can be useful in differentiating between recurrent tumor and radiation necrosis. In everyday practice, the visual assessment of diffusion-weighted and perfusion images may also be helpful by favoring one diagnosis over the other, with restricted diffusion and an elevated relative cerebral blood volume being seen much more frequently in recurrent tumor than in radiation necrosis.

Innovative Hypofractionated Stereotactic Regimen Achieves Excellent Local Control With No Radiation Necrosis: Promising Results in the Management of Patients With Small Recurrent Inoperable GBM

“…Lastly, a short follow-up duration could account for the lack of RN observed. However, median survival time amongst the five survivors in the present study was 23.3 months, which falls within the 2 -23 months period where RN is most likely observed [31]. For instance, Floyd, et al [38] reported survival of patients with brain necrosis at 23, 20, and nine months.…”

“…RN can be seen between two to 23 months following radiation therapy [31]. RN was assessed subjectively using advanced MR imaging including diffusion-weighted imaging (DWI), apparent diffusion coefficient (ADC) mapping, MR spectroscopy, and PET.…”

“…RN was assessed subjectively using advanced MR imaging including diffusion-weighted imaging (DWI), apparent diffusion coefficient (ADC) mapping, MR spectroscopy, and PET. Factors suggestive of RN include 1) increased proportion of hypointensity on a T2-weighted MR image compared to the same area on a contrast-enhanced T1-weighted image and 2) any complete lack of perfusion, while ruling out the presence of a nodular highly vascularized area, within a contrast-enhanced lesion on perfusion MRI [31]. All patients suspicious for RN underwent MR spectroscopy and PET, where tumor progression was suspected for a standardized uptake value (SUV)/background threshold ratio > 1.5.…”

Postoperative Imaging and Surveillance in Large Nerve Perineural Spread

“…The risk increases with the radiation dose given as well as the type of radiation and technique used. 16 Given the proximity of the cranial nerves and skull base to the parenchyma, it may be encountered in the setting of treatment for perineural spread (PNS). On imaging, this will present as a focal area of abnormal T2 high signal with central necrosis and peripheral enhancement, predominantly involving white matter (►Fig.…”

Exploration of the Recurrence of Radiation Brain Necrosis After Bevacizumab Discontinuation

“…Moreover, it is difficult to ask patients with multiple intracranial [12]. In this study, the patients were diagnosed based on a comprehensive medical history, symptoms, signs, MRI, spectroscopy and positron emission tomography-computed tomography (PET-CT) [13][14][15][16][17][18][19][20]. MRI or spectroscopy was performed first, and then, PET-CT was performed as needed for ambivalent diagnoses.…”