The Value of Baseline [18F]FDG-PET in Predicting the Progression-Free Survival in Patients with Thymic Epithelial Tumours: A Systematic Review and Meta-Analysis.

Background/Objectives: [¹⁸F]FDG-PET is often used for staging thymic epithelial tumours (TETs). However, its prognostic role remains uncertain. The aim of this present systematic review and meta-analysis is to assess the prognostic value of baseline [¹⁸F]FDG-PET-derived semiquantitative parameters in predicting progression-free survival (PFS) in patients with TETs. Methods: A systematic review and meta-analysis were conducted according to PRISMA guidelines. PubMed, Embase, and Scopus databases were searched up to 30 May 2025. Studies evaluating the prognostic impact of [¹⁸F]FDG-PET parameters on PFS in TETs were included. Pooled hazard ratios (HRs) with 95% confidence intervals (CIs) were calculated. Results: Six retrospective studies involving 593 patients were included. Maximum standardized uptake value (SUVmax), analysed as a continuous variable in four studies, significantly predicted worse PFS (HR: 1.18, 95% CI: 1.08-1.29, p < 0.001), with high inter-study heterogeneity (I² = 79.7%). When dichotomized (two studies), higher SUVmax was associated with significantly poorer PFS (HR: 9.00, 95% CI: 2.93-27.71). Similarly, mean SUV (SUVmean) as a continuous predictor was also significantly associated with impaired PFS (HR: 1.41, 95% CI: 1.25-1.59), but only two studies assessed this parameter. Conversely, metabolic tumour volume (MTV) and total lesion glycolysis (TLG), both assessed as continuous prognosticators, did not show a significant prognostic value. Notably, in both MTV and TLG analyses, two studies contributed a weight of 0%, reflecting limited precision and highlighting the need for larger data. Conclusions: Baseline [¹⁸F]FDG-PET parameters such as SUVmax and SUVmean showed a potential prognostic value in patients with TETs. However, these results are based on a limited number of retrospective studies with significant heterogeneity. Prospective multicentre investigations are necessary to confirm the potential role of [¹⁸F]FDG-PET for risk stratification in TETs.