Benjamin Nicaise

Background: Radiotherapy is essential for skull base tumor management but carries the risk of radiation-induced brain injury (RIBI). This spectrum ranges from transient radiation-induced contrast enhancement (RICE) to irreversible necrosis. Distinguishing these entities from tumor progression is critical, particularly with the increasing adoption of proton therapy. Methods: A comprehensive narrative review of the peer-reviewed literature was conducted up to October 1, 2025. The search strategy focused on adult patients treated for skull base malignancies, synthesizing data on dose–volume metrics, incidence rates, and modality-specific toxicity profiles. Results: RIBI represents a pathophysiological continuum. (a) Descriptive imaging patterns: In prospective proton therapy series, focal RICE occured in 15% of patients, typically at a median of 12 months, and often resolved spontaneously. (b) Modality comparison: Although proton therapy reduces integral brain dose versus photon therapy, elevated linear energy transfer (LET) at the distal Bragg peak may contribute to focal radiation-associated image changes (RAIC), particularly in the temporal lobes. (c) Risk stratification and diagnosis: Risk increased when >1% of the healthy brain received >57.6 Gy (Relative Biological Energy (RBE)) or when V67Gy exceeded 0.17 cc. Advanced MRI and amino acid positron emission tomography (PET) improved differentiation between radiation effects and tumor recurrence. Conclusions: Post-radiation imaging changes are common and often benign. Distinguishing RICE from progression requires multimodal imaging and adherence to specific dose constraints. Management should prioritize surveillance for asymptomatic lesions.

Background: Radiotherapy is an essential component for the treatment of skull skull‑base tumours. However, radiation‑induced brain injury (RIBI) appearing on magnetic resonance imaging (MRI) as pseudoprogression, radiation‑induced contrast enhancement (RICE), radiation necrosis, and other contrast‑enhancing brain lesions—remains an important late toxicity which is not very well characterized. Clarifying adult‑specific patterns, the role of positron emission tomography (PET), and differences between proton and photon therapy is clinically relevant. Methods: Narrative review of peer‑reviewed literature to 1 October 2025 focused on adult chordoma, chondrosarcoma, meningioma, adenoid cystic carcinoma, pituitary adenoma, craniopharyngioma, undifferentiated carcinoma of nasopharyngeal type (UCNT), and germinoma. Results: Radiation-induced brain injury (RIBI) may range from early transient brain oedema/enhancement to late necrosis. Lesions cluster in temporal and frontal lobes after skull‑base irradiation. Proton therapy generally reduces high‑dose exposure versus photons and is associated with fewer severe necrotic events, though asymptomatic RICE is common. Advanced MRI (diffusion, perfusion, spectroscopy, ASL, amide proton transfer) and positron emission tomography (PET) with Fluorodeoxyglucose (FDG) and amino‑acid tracers aid distinction between treatment effect and progression. Risk reflects dose–volume metrics, prior irradiation, and patient comorbidities. Conclusions: MRI/PET alterations after skull‑base radiotherapy vary by modality, dose, and tumor context. Integrating multimodal imaging with clinical factors should guide surveillance and management; prospective validation is needed.