A Challenging Differential Diagnosis Between Brain Radionecrosis and Recurrent Metastatic Disease, with Temporary Clinical/Radiological Response to Bevacizumab and Later Imaging Suspicious for Oligoprogression

Background: Brain radiation necrosis is a side effect of radiotherapy that can occur months, or even years, after the end of treatment. From an anatomical–pathological perspective, it is characterized by avascular damage, demyelination, and necrosis. Methods: We present a case of a patient with breast cancer cT2N1M0 and multiple brain metastases occurring at 2 years after diagnosis, who was treated with whole-brain radiotherapy (WBRT) and Stereotactic Radiotherapy (SRT) for tumor progression. Dynamic imaging revealed right parietal post-therapeutic changes in aggravation, requiring differential diagnosis between tumor progression (TP) and brain radionecrosis (BRN). Results: Brain radionecrosis and tumor progression are difficult to differentiate due to their similar radiological and clinical characteristics. MRI perfusion plays an important role in differentiating the two entities. Conclusions: Differentiating radiation necrosis from a recurrent tumor is crucial for appropriate treatment. Medical management includes corticosteroids as first-line treatment, after which bevacizumab is administered as secondary therapy.