The determination of prognoses for patients with recurrent glioblastoma remains challenging. This study aimed to evaluate the prognostic value of static O-(2-18F-fluoroethyl)-l-tyrosine (18F-FET) PET parameters in patients with recurrent glioblastoma. Methods: We retrospectively evaluated patients treated in 3 institutional clinical trials examining vascular endothelial growth factor inhibition, immune checkpoint inhibition, or their combination in recurrent glioblastoma. Patients with a baseline 18F-FET PET were included in the analysis and stratified by treatment group. Prognostic value was evaluated using univariate Kaplan-Meier and multivariate Cox regression analyses, with receiver-operating-characteristic analysis to identify optimal thresholds. Results: Both univariate and multivariate analysis revealed that patients with a larger baseline metabolic tumor volume (MTV) and higher mean tumor-to-background ratio (TBRmean) had an increased risk of death independent of treatment (MTV per 10 mL: hazard ratio, 1.06; 95% CI, 1.01-1.12; P = 0.023; TBRmean: hazard ratio, 1.91; 95% CI, 1.14-3.21; P = 0.014). Receiver-operating-characteristic analysis showed that an MTV and TBRmean of more than 27.94 cm3 and 2.15, respectively, identified patients with worse overall survival in our patient population. Conclusion: Pretreatment MTV and TBRmean had a significant prognostic value in patients with recurrent glioblastoma, independent of treatment, and could be useful to stratify and select patients for future clinical trials.
Geens et al. (Thu,) studied this question.