P18.04.A APPLICATION OF THE PET RANO 1.0 CRITERIA IN DIFFUSE GLIOMA: RETROSPECTIVE SINGLE CENTER EXPERIENCE

• Published in: Neuro-oncology (Charlottesville, Va.) Va.), 2024-10, Vol.26 (Supplement_5), p.v95-v96
• Main Authors: Wiegand, L, Barci, E, Müller, K J, Forbrig, R, Brendel, M, Preusser, M, Schönecker, S, Thon, N, Harter, P N, von Baumgarten, L, Albert, N L
• Format: Article
• Language: English
• ISSN: 1522-8517; 1523-5866
• DOI: 10.1093/neuonc/noae144.320

Abstract BACKGROUND Response evaluation and disease monitoring of gliomas relies on MRI in clinical routine and trials. Recently, novel response criteria utilizing amino acid PET (PET RANO 1.0) have been introduced. This study analyses longitudinal [18F]FET PET data of patients with diffuse glioma and applies the PET RANO 1.0 criteria to describe PET characteristics at baseline, response classes, and changes of individual parameters. MATERIAL AND METHODS In this retrospective single-center study, patients with diffuse glioma and a baseline as well as at least one follow-up [18F]FET PET scan were identified. PET analyses were performed according to the PET RANO 1.0 criteria and included the assessment of maximal and mean target-to-background ratios (TBRmax, TBRmean), PET volume, changes of these values between scans, and the presence of either measurable or no / non-measurable disease. Follow-up scans were classified as PET-based progressive disease (PET-PD), stable disease (PET-SD), partial response (PET-PR), or complete response (PET-CR) according to PET RANO 1.0. RESULTS A total of 475 scans in 148 patients were evaluated with a total of 228 treatment lines, defined as a baseline scan plus a series of one to four follow-up evaluations either with or without treatment. Overall, 164/228 baseline scans had measurable disease and 64/228 had non-measurable or no measurable disease. In the treatment lines, 4% of patients had PET-CR as best response, 23% had PET-PR, 37% had PET-SD, and 36% had PET-PD. PET-PD was determined based on significant volume changes and/or the occurrence of new lesions in the majority of cases (>90%), while significant increases of uptake intensity were found in 30% of cases. A sole increase of uptake intensity as determinant for PET-PD was only found in 8% of cases. PET-PR was determined based on volume reductions in 82% of cases (25% in combination with decreasing uptake intensity) and by a sole reduction of uptake intensity in 18% of cases. Treatment lines of glioblastoma had PET-PD as a best response in 56% of cases, while astrocytomas and oligodendrogliomas only had PET-PD in 44% and 35% of cases, respectively. CONCLUSION This study demonstrates that significant volume changes seem to be the major determinant for treatment response according to the PET RANO 1.0 criteria and are often accompanied by changes of uptake intensity, while sole uptake intensity changes determine response classes only in a subset of patients. Best respons