Case of the Week
Section Editors: Matylda Machnowska1 and Anvita Pauranik2
1University of Toronto, Toronto, Ontario, Canada
2BC Children's Hospital, University of British Columbia, Vancouver, British Columbia, Canada
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November 8, 2018
Radiation necrosis mimicking tumor progression
- Background
- Radiation-induced changes mostly result from injury to the small vessels, such as hyalinization, fibrinoid necrosis, and thrombosis.
- Histologically, radiation-induced injury has been described as an area of necrosis surrounded by an inflammatory cell infiltrate.
- Clinical Presentation
- Variable, patients with radiation necrosis may be symptomatic or asymptomatic. The symptoms depend on the location of lesions, degree of surrounding edema, and mass effect.
- Key Diagnostic Features
- Differentiating between tumor progression and radiation necrosis using conventional MRI is difficult. Therefore, a combination of ADC with rCBV may add value in correct differentiation between these two entities.
- Layering pattern of ADC has been reported to be highly specific for radiation necrosis.
- Mature radiation necrosis may show a layering pattern with an inner layer of complete necrosis and liquefaction (increased ADC), surrounded by a transition layer with low ADC-values.
- Surrounding the liquefied center in radiation necrosis, more active inflammatory responses commonly occur, resulting in some degree of increased rCBV. However, rCBV-values are typically only slightly-to-moderately increased.
- Differential Diagnosis
- Tumor progression: The imaging parameters to differentiate both entities are discussed in the above section
- Treatment
- Most imaging abnormalities in radiation necrosis are transient. In our patient, imaging performed 3-months later showed spontaneous, nearly complete resolution of contrast enhancement and normalization of rCBV.
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