Can PET/CT be used more effectively in pleural effusion evaluation?

Purpose: Sometimes, characterization of pleural effusion (PE) can be challenging especially in patients whom invasive procedures/recurrent invasive procedures cannot be performed. The main purpose of the study is to answer this question, Can F-FDG-PET/CT contribute to reduction in the number of invasive procedures or patients undergoing to invasive procedures? Results may increase the effectiveness of patient management by facilitating clinical decision-making, especially in patients who cannot undergo invasive/recurrent invasive procedures.

Methods: Sixty-seven patients' F-FDG-PET/CT, pleural fluid cytologies (PFCs) and, if any, pleural biopsies were re-assessed. If patient's PFC/biopsy was malignant, effusion was considered as malignant. If two consecutive PFCs were negative in patients without biopsy, effusion was considered as benign. Characterization was based on consensus with baseline/follow-up F-FDG-PET/CT and clinical parameters in patients with one negative PFC (n = 6).

Results: None of the F-FDG-PET/CT parameters could characterize PE alone. However, if PE maximum standardized uptake value (SUV) > 1.3 or PE SUV/mean standardized uptake value of mediastinal blood pool (MBP SUV) > 1.2 was combined with at least one of the following, specificity and positive predictive value (PPV) were 100%, accuracy was around 90%. Diffuse-nodular/nodular pleural thickness, post-obstructive atelectasis, nodule/mass with SUV > 2.5 in lung, multiple pulmonary nodules. All 29 patients who had SUV > 1.3 together with at least one of the mentioned four parameters diagnosed malignant pleural effusion (MPE). However, sensitivity and negative predictive value (NPV) were still insufficient.

Conclusion: Patients who have contraindications for invasive diagnostic methods, and meet the aforementioned criteria may be considered as MPE primarily. On the other hand, if PE SUV < 1.3 or PE SUV/MBP SUV < 1.2 with the negativity of the all four parameters mentioned above, it is difficult to say that this can be considered as benign pleural effusion (BPE) according to our results.