Potential of dual time point FDG-PET imaging in differentiating malignant from benign pleural disease

The aim of this study was to assess the utility of dual time point 18F-fluorodeoxyglucose positron emission tomography (18F-FDG-PET) imaging in differentiating benign from malignant pleural disease.

Fifty-five consecutive patients of suspected malignant pleural mesothelioma (MPM) and recurrence of MPM who were referred for the evaluation underwent two sequential 18F-FDG-PET scans (dual time point imaging). The average percent change in the maximum standardized uptake values (Delta%SUVmax) of the lesion/lesions between time point 1 (SUV(max1)) and time point 2 (SUV(max2)) was calculated. All PET results were correlated with the histopathological or cytopathology results. Patients were divided into three principal groups (A = newly diagnosed MPM, B = recurrent MPM, and C = benign pleural disease). The parameters of 18F-FDG uptake (SUV(max) values and its changes over time) were compared among groups.

Among the 55 patients who had undergone dual time point 18F-FDG-PET studies, 44 were diagnosed with MPM (28 newly diagnosed and 16 had recurrence). The PET studies demonstrated 229 malignant pleural lesions in these patients. The remaining 11 patients were proven to have benign pleural disease. The mean +/- SD of the SUV(max1), SUV(max2), and the Delta%SUV(max) of the all lesions of each patient in groups A, B, and C were 5.0 +/- 2.2%, 5.8 +/- 2.8%, and 12.8 +/- 8.4%; 4.6 +/- 1.7%, 5.3 +/- 2.0%, 13.8 +/- 9.2%; and 1.6 +/- 0.4%, 1.4 +/- 0.3%, and-9.6 +/- 19.1%, respectively. The mean +/- SD of the SUV(max1), SUV(max2), and Delta%SUV(max) in patients with both newly diagnosed and recurrent MPM were significantly higher than those of benign pleural disease group (p < 0.0001). For each patient, the most intense (hottest) lesion's SUV(max1), SUV(max2), and Delta%SUV(max) were also compared among the aforementioned groups, and these results again confirmed that MPM lesions had significantly higher values than those of benign pleural lesions (p < 0.0001).

There is an increasing uptake of (18)F-FDG over time in pleural malignancies, whereas the uptake in benign pleural disease generally stays stable or decreases over time. Therefore, dual time point imaging appears to be an effective approach in differentiating benign from malignant pleural disease, which increases the sensitivity and is also helpful in guiding the biopsy site for a successful diagnosis.