Diagnostic Ability of FDG-PET/CT in the Detection of Malignant Pleural Effusion

Abstract

We investigated the role of F-18 fluorodeoxyglucose (FDG)-positron emission tomography (PET)/computed tomography (CT) for the differential diagnosis of malignant and benign pleural effusion. We studied 36 consecutive patients with histologically proven cancer (excluding malignant mesothelioma) who underwent FDG-PET/CT for suspected malignant pleural effusion. Fourteen patients had cytologically proven malignant pleural effusion and the other 22 patients had either negative cytology or clinical follow-up, which confirmed the benign etiology. We examined the maximum standardized uptake values (SUV max) of pleural effusion and the target-to-normal tissue ratio (TNR), calculated as the ratio of the pleural effusion SUV max to the SUV mean of the normal tissues (liver, spleen, 12th thoracic vertebrae [Th12], thoracic aorta, and spinalis muscle). We also examined the size and density (in Hounsfield units) of the pleural effusion and pleural abnormalities on CT images. TNR (Th12) and increased pleural FDG uptake compared to background blood pool were significantly more frequent in cases with malignant pleural effusion (P < 0.05 for both). The cutoff TNR (Th12) value of >0.95 was the most accurate; the sensitivity, specificity, and accuracy for this value were 93%, 68%, and 75%, respectively. FDG-PET/CT can be a useful method for the differential diagnosis of malignant and benign pleural effusion.

FIGURE 1

(A) An 80-year-old man was found to have a right pleural effusion after the resection of right lung adenocarcinoma. A weak but obvious FDG uptake was found along the right pleura (arrow). SUVmax of this lesion was 1.41 and TNR with the reference of Th12 was 1.21. Malignant pleural effusion was diagnosed by thoracocentesis. (B) A 60-year-old woman developed a right pleural effusion after the resection of colon cancer. No definite FDG accumulation was observed, SUVmax = 1.07, TNR (Th12) = 0.88. Cytopathologic examination of pleural fluid was negative for malignancy. It finally disappeared after the treatment of heart failure. FDG = fluorodeoxyglucose, SUVmax = maximum standardized uptake value, Th12 = 12th thoracic vertebrae, TNR = target-to-normal tissue ratio.