TOPLINE:

In a parallel randomised trial, O-(2-[18F]fluoroethyl)-L-tyrosine (FET)-PET led to comparable survival outcomes to contrast-enhanced T1-weighted (CE-T1) MRI for re-irradiation planning in patients with recurrent glioblastoma.

METHODOLOGY:

• Researchers conducted a multicentre, open-label, parallel randomised trial at 15 radiation oncology centres in Germany and included 200 adult patients with recurrent glioblastoma (43% women) between November 2013 and August 2021.
• Patients were randomly assigned in a 1:1 ratio to receive FET-PET-based re-irradiation (n = 100) or CE-T1 MRI-based re-irradiation (n = 100). Patients received stereotactic re-irradiation with a total dose of 39 Gy delivered in 13 fractions of 3 Gy/d, five times per week, based on their assigned imaging modality for target volume definition.
• The primary endpoint was progression-free survival from randomisation until disease progression or death, whereas secondary endpoints included safety, overall survival, and locally controlled survival.

TAKEAWAY:

• After a median follow-up duration of 4.1 months, the median progression-free survival was 4.0 months (95% CI, 3.7-5.2) in the FET-PET group compared with 4.9 months (95% CI, 3.7-6.0) in the CE-T1 MRI group (adjusted hazard ratio [aHR], 1.14; P = .39).
• After a median follow-up duration of 12.2 months, the median overall survival reached 9.4 months (95% CI, 7.8-11.1) in the FET-PET group compared with 9.0 months (95% CI, 7.6-10.5) in the CE-T1 MRI group (aHR, 1.01; P = .92).
• After a median follow-up duration of 6.3 months, the median locally controlled survival was 6.3 months (95% CI, 5.1-7.2) in the FET-PET group compared with 6.8 months (95% CI, 6.2-7.3) in the CE-T1 MRI group (aHR, 1.20; P = .25).
• Radionecrosis of any grade occurred in 25% of patients in the FET‑PET group and 21% of patients in the CE‑T1 MRI group. Serious adverse events affected 15% of patients in both groups within 30 days after re‑irradiation and 10% of patients in the FET‑PET group vs 19% of those in the CE‑T1 MRI after 30 days. No treatment‑related deaths were reported.

IN PRACTICE:

"The study showed the safety of the FET-PET examination and implemented a standardised method for FET-PET-based target volume definition for recurrent glioblastoma, which leads to similar oncological outcomes as the traditional MRI-based treatment," the authors wrote, concluding that "these prospective data provide valuable information on the oncological efficacy and side-effect profile of cerebral re-irradiation and support the radiotherapy process in recurrent glioblastoma."

SOURCE:

The study was led by Anca-Ligia Grosu, MD, Department of Radiation Oncology, Medical Center-University of Freiburg, Freiburg, Germany, and Wolfgang A. Weber, MD, Department of Nuclear Medicine, School of Medicine and Health, Technical University Munich, Munich, Germany. It was published online on December 19, 2025, in The Lancet Oncology.

LIMITATIONS:

Not all patients had histologically confirmed recurrence. In the CE-T1 MRI group, only contrast-enhancing lesions were considered. The authors used static PET rather than a combination of static and dynamic parameters that provides a higher diagnostic accuracy. Additionally, the trial design did not report on isocitrate dehydrogenase mutation status.

DISCLOSURES:

This study was funded by Deutsche Krebshilfe. One author reported receiving institutional grants from Varian Medical Systems/Siemens Healthineers, Novocure, German Cancer Aid, German Research Foundation, and the Federal Ministry of Education and Research. Several others reported receiving grants, consulting fees, and honoraria or travel support and serving on advisory boards for AstraZeneca, Novocure, TME Pharma, and various other organisations. Full disclosures are noted in the original article.

This article was created using several editorial tools, including AI, as part of the process. Human editors reviewed this content before publication.