Value of SUVmax in differentiation of benign and malignant pleural effusion

ABSTRACT Objectives: We aimed to investigate the importance of maximum standardized uptake (SUVmax) value and its correlation with cytopathology results in differentiation between benign and malignant pleural effusions. Materials and Methods: In this study, patients from Dicle University Faculty of Medicine, and Diyarbakır Education and Research Hospital in whom 18F-FDG-PET/CT had been performed for any indications were analyzed retrospectively. Patients with the PET / CT reports in which there were pleural effusion were evaluated without distinguishing primary pathology, suspicion of malignancy or known malignancy. Of the cases with cytopathologic examination, having FDG involvement or not with pleural effusion, 21 males / 15 females, totally 36 cases were included in this study. Pleural effusions detected in PET / CT scanning were analyzed by comparing the SUVmax values and cytopathologic results. In statistical analysis, a Mann-Whitney U test and a Chi-square (?2) test was used. Hypotheses were bi-directional and p ? 0.05 was considered statistically significant. Results: In this study, 21 males with the mean age of 54.2 years and 15 females with the mean age of 57.1 years, totally 36 cases with pleural effusions were studied. 21 patients (58.3%) were diagnosed with benign and 15 (41.7%) with malignant by cytopathologic examination. In retrospective survey, It was found that 20 patients (12 of them were diagnosed with mesothelioma, 5 with pleuritis, 3 with tumor negative normal pleural tissue) had had pleural biopsy. Primary pathology of the remaining 16 patients were: 7 with lung ca., 1 with pancreas ca., 1 with unknown primary adenocarcinoma, 1 followed patient with a solitary pulmonary nodule, 1 with tuberculosis and 5 with unknown primary pleural effusion suspicious for malignancy. The lowest SUVmax value was 0.6 and the highest was 3.2 and mean of the all patients was calculated as 1.55 ± 0.72; the mean SUVmax in benign group was 1.47 ± 0.6; the mean SUVmax in malignant group was 1,66 ± 0.8. In our study, statistical analysis has shown that there was not any statistically significant difference between SUVmax values of benign and malignant pleural effusion (p=0.585). SUVmax of 5 malignant patients was determined as <1.0, <2.0 in 10 malignant patients and > 2.0 in 5 benign patients. Conclusions: In our study, the direct relation in pleural effusion between SUVmax, malignant, and benign in patients with known / unknown primary malignancy or unknown primary pleural effusion suspicious for malignancy was not determined. Patients with low SUVmax might be malignant under clinical suspicion and patients with high SUVmax might also be benign. Therefore, diagnosis and treatment algorithm should be carried on carefully. We also think that there is a need for new prospective studies with larger patient groups to determine a cut-off value of FDG uptake (SUVmax) in differentiation of malignant pleural effusions from a benign process. KEY WORDS: Pleural effusion, malignant, benign, SUVmax, FDG-PET/CT