Differentiating glioma recurrence from radiation necrosis: a narrative review of positron emission tomography and magnetic resonance imaging and their diagnostic accuracies.

BACKGROUND AND

OBJECTIVE

Differentiating glioma recurrence from radiation necrosis remains a critical diagnostic challenge in neuro-oncology due to overlapping imaging features. Positron emission tomography (PET) and magnetic resonance imaging (MRI) offer complementary metabolic and structural information that may enhance diagnostic accuracy. This narrative review evaluates the performance of PET, advanced MRI techniques, and their integration in distinguishing tumour recurrence from post-treatment effects.

METHODS

A comprehensive search of PubMed, Medline, and Embase databases was conducted to identify studies published after April 2020. Inclusion criteria comprised studies on histologically diagnosed gliomas using PET and MRI, reporting sensitivity, specificity, or accuracy.

KEY CONTENT AND FINDINGS: Eight cohort studies met the inclusion criteria, examining PET tracers (18F-FDG, 18F-FET, 11C-MET, 18F-DOPA) and advanced MRI techniques [diffusion kurtosis imaging (DKI), dynamic susceptibility contrast (DSC) perfusion, magnetic resonance spectroscopy (MRS)]. The integration of PET and MRI outperformed standalone modalities in diagnostic accuracy in all but one study. 18F-FET PET demonstrated high diagnostic accuracy, with sensitivity up to 95% and no diagnostic improvement when combined with MRI in high-grade glioma, though its availability remains limited. MRI alone had variable sensitivity (33-77%) and specificity (50-100%), depending on the technique and tracer used. DKI showed promise in enhancing sensitivity (72-100%). Heterogeneity in protocols and patient cohorts limited direct comparisons across studies.

CONCLUSIONS

The combination of PET and MRI provides a superior diagnostic approach for differentiating glioma recurrence from radiation necrosis, with 18F-DOPA PET and advanced MRI sequences emerging as the most effective pairing. Further multicenter studies with standardized protocols are required to validate these findings and address challenges related to tracer accessibility and protocol variability. These advancements have the potential to optimize patient management in neuro-oncology.