What question did this study set out to answer?

To assess the diagnostic and prognostic capabilities of dynamic 18F-FET PET in differentiating pseudoprogression from tumor recurrence after radiotherapy for glioblastoma.

April 4, 2026Open Access

Utility of dynamic 18F-FET PET in determining pseudoprogression from tumour recurrence in the six months following radiation therapy for glioblastoma

Key Points

To assess the diagnostic and prognostic capabilities of dynamic 18F-FET PET in differentiating pseudoprogression from tumor recurrence after radiotherapy for glioblastoma.
Analyzed data from 66 glioblastoma patients undergoing FET-PET within six months post-radiotherapy.
Evaluated static metrics including SUVmax and TBRmax alongside dynamic TAC morphology (Types 1-3).
Utilized receiver-operating-characteristic analysis, logistic regression, and sensitivity analyses for diagnostic performance.
Analyzed overall survival using Kaplan-Meier and Cox regression methods.
35 patients (53%) had tumor recurrence while 31 (47%) demonstrated pseudoprogression.
TAC morphology had an AUC of 0.76, outperforming static metrics (SUVmax AUC 0.66, TBRmax AUC 0.57).
TAC morphology was the only independent predictor of recurrence with an odds ratio of 4.62 (p = 0.010).
Median overall survival was 10.2 months for recurrence compared to 20.5 months for pseudoprogression (p < 0.0001).
Stratification by TAC type showed median OS of 11.7 months (Type 1), 9.9 months (Type 2), and 8.8 months (Type 3; log-rank p = 0.041).

Abstract

Abstract Background Distinguishing early recurrence from pseudoprogression after chemoradiotherapy remains a major challenge in glioblastoma. Although 18-F-fluroethyl-L-tyrosine (FET)-PET is increasingly used, reliance on static thresholds limits accuracy in the early post-radiotherapy period. The role of dynamic time-activity-curve (TAC) patterns in this setting is not well defined. We evaluated the diagnostic and prognostic performance of TAC morphology compared with static uptake metrics. Methods Sixty-six patients with glioblastoma underwent FET-PET within six months of radiotherapy. Final diagnosis was determined by histopathology (n = 15) or predefined clinical endpoints (n = 51). Static metrics (SUVmax, TBRmax) and dynamic TAC morphology (Types 1-3) were assessed. Diagnostic performance was assessed by receiver-operating-characteristic analysis, logistic regression, and sensitivity analyses. Overall survival (OS) was analysed with Kaplan-Meier and Cox regression. Results Thirty-five patients (53%) had recurrence and 31 (47%) pseudoprogression. TAC morphology demonstrated the highest diagnostic accuracy (AUC 0.76; sensitivity 68.8%; specificity 94.7%; PPV 93.6%; NPV 72.9%), outperforming SUVmax (AUC 0.66) and TBRmax (AUC 0.57). TAC morphology was the sole independent predictor of recurrence (OR 4.62; p = 0.010). Median OS was significantly shorter in recurrence compared with pseudoprogression (10.2 vs 20.5 months; p 0.0001). TAC type stratification revealed median OS of 11.7 months (Type 1), 9.9 months (Type 2), and 8.8 months (Type 3; log-rank p = 0.041). Sensitivity analysis excluding patients with diagnostically ambiguous ground truth (n = 14) confirmed that TAC pattern remained a significant predictor of diagnosis (AUC 0.75; p = 0.012). Conclusions Dynamic FET-PET improves diagnostic specificity and provides prognostic insight beyond static uptake metrics. TAC patterns offer a structured framework for improving diagnostic certainty and guiding therapeutic decisions.

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Cite This Study

Jang et al. (Wed,) studied this question.

synapsesocial.com/papers/69d0afc7659487ece0fa5e99 https://doi.org/https://doi.org/10.1093/noajnl/vdag085

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