Metabolic significance of the pattern, intensity and kinetics of 18F-FDG uptake in malignant pleural mesothelioma

Background: Malignant pleural mesothelioma is an aggressive neoplasm with a highly variable course. This pilot study evaluated the significance of the pattern, intensity and kinetics of F-18-FDG uptake in mesothelioma in the context of histopathology and surgical staging. Methods: Sixteen consecutive patients with pleural disease on CT scan underwent F-18-FDG imaging. Imaging was performed with a dual detector gamma camera operating in coincidence mode. Semiquantitative image analysis was performed by obtaining lesion-to-background ratios (F-18-FDG uptake index) and calculating the increment of F-18-FDG lesion uptake over time ( malignant metabolic potential index (MMPi)). Results: Twelve patients had histologically proven malignant mesotheliomas ( 10 epithelial, two sarcomatoid). Thirty two lesions were positive for tumour. Patterns of uptake matched the extent of pleural and parenchymal involvement observed on CT scanning and surgery. Mean (SD) F-18-FDG uptake index for malignant lesions was 3.99 (1.92), range 1.5 - 9.46. Extrathoracic spread and metastases had higher F-18-FDG uptake indices (5.17 (2)) than primary (3.42 ( 1.52)) or nodal lesions (2.99 ( 1)). No correlation was found between histological grade and stage. The intensity of lesion uptake had poor correlation with histological grade but good correlation with surgical stage. F-18-FDG lesion uptake increased over time at a higher rate in patients with more advanced disease. The MMPi was a better predictor of disease aggressiveness than the histological grade. Conclusions: This pilot study suggests that the pattern, intensity, and kinetics of F-18-FDG uptake in mesothelioma are good indicators of tumour aggressiveness and are superior to the histological grade in this regard.