Radiation necrosis presenting as pseudoprogression (PsP) during alectinib treatment of previously radiated brain metastases in ALK-positive NSCLC: Implications for disease assessment and management

Treatment-related necrosis of previously SRS-treated brain metastasis during alectinib treatment can present as PsP. It may be impossible to distinguish PsP from true disease progression without a pathologic examination from resected sample. High degree of clinical suspicion, close monitoring and more sensitive imaging modalities may be needed to distinguish PsP versus progression in radiated brain lesions during alectinib treatment especially if there is no progression extra-cranially.