Malignant Pleural Mesothelioma (MPM) Evaluation with [11C]-Methionine PET/CT Before and After Talc Pleurodesis

Molecular Imaging and Biology 2026 March 9 [Link]

Egesta Lopci, Angelo Castello, Alberto Testori, Emanuele Voulaz, Daoud Rahal 5, Matteo Perrino 6, Alessandro Crepaldi 3, Giorgio Maria Ferraroli 3, Valentina Errico 3, Edoardo Bottoni 3, Marcello Rodari 7, Lorenzo Muraglia 2, Giuseppe Marulli 3 4, Marco Alloisio, Paolo Andrea Zucali

Abstract

Background: Malignant pleural mesothelioma (MPM) poses an imaging challenge that requires special attention, especially in patients who have undergone talc pleurodesis. [18F]FDG PET/CT (FDG PET) is a validated imaging modality in oncology that has proven useful for detecting malignant pleural lesions. However, the inflammatory reaction induced by pleurodesis renders its interpretation unreliable. In this study, we assessed in parallel the role of [11C]Methionine PET/CT (MET PET) and FDG PET in MPM patients before and after talc pleurodesis.

Materials and methods: We prospectively enrolled 30 consecutive patients with clinical suspicion of MPM who were referred to our Institution from September 2014 to February 2016 for talc pleurodesis. The study was approved and registered at ClinicalTrials.gov (NCT02519049). Patients underwent assessment at baseline and after pleurodesis with two consecutive scans: FDG PET (standard imaging) and MET PET (experimental imaging). Semi-quantitative parameters were defined for both scans and statistically compared to pathological findings from video-assisted thoracoscopy (VATS), including SUVmax, SUVmean, metabolic tumor volume (MTV) and total lesion glycolysis for FDG PET or metabolic tumor burden (TLG or MTB = MTV x SUVmean) for MET PET.

Results: Twenty patients (M:F = 18:2; median age, 72 years) with MPM (18 epithelioid, 2 non-epithelioid) completed all study investigations. All tumors showed increased uptake of both FDG and MET PET. After talc pleurodesis, FDG PET showed a significant increase in mean and median MTV (P = 0.0005 and 0.0003, respectively) and mean and median TLG (P = 0.0172 and 0.0028, respectively). In contrast, MET PET parameters showed significant increases in mean and median SUVmax (P = 0.0208 and 0.0209, respectively) and SUVmean (P = 0.0106 and 0.0109, respectively) compared to baseline. There was a significant negative correlation between SUVmax, MTV and MTB/TLG and the percentage change at the early assessment post-pleurodesis for both MET PET (rho = -0.645, P < 0.01; rho = -0.517, P = 0.013; rho = -0.528, P = 0.011, respectively) and FDG PET (rho = -0.808, P < 0.01; rho = -0.781, P < 0.01; rho = -0.888, P < 0.01, respectively). The percentage change in SUVmax was significantly greater in FDG PET than for MET PET (+ 19% vs + 16%, P = 0.03). Additionally, mean and median MTV were significantly higher on FDG PET than MET PET (mean + 1022.3 vs + 224.2, P = 0.01; median + 157.5 vs + 7.1, P = 0.02).

Conclusions: This study confirms the impact of talc pleurodesis on FDG PET, particularly for volumetric parameters (MTV and TLG). MET PET appears less influenced by post-pleurodesis inflammatory reaction than FDG PET, with changes mostly limited to SUVmax and SUVmean. Clinical Trial Number (NCT02519049)