PET for the evaluation of pleural thickening observed on CT

Early discrimination between benign and malignant pleural diseases is vital for the treatment and prognosis of a patient. Imaging is traditionally performed with CT or MRI, with an accuracy of 50%-75%. PET has proven to be superior as a diagnostic tool in several malignancies. In this prospective study, PET results in patients with pleural abnormalities on CT were compared with histologic results.

Eligible patients had pleural thickening on CT and were medically fit for surgical diagnostic procedures. All patients underwent PET. Qualitative assessment led to a PET score of 1 (definitely normal), 2 (probably normal), 3 (probably abnormal), or 4 (definitely abnormal). PET scores of 1 or 2 indicated a negative PET finding, whereas PET scores of 3 or 4 indicated a positive PET finding. Pathologic verification techniques included thoracocentesis, thoracoscopy, or open pleural biopsy at thoracotomy.

Thirty-two patients were enrolled, 19 with malignant and 13 with benign pleural disease. PET was true positive in 18 and true negative in 12 patients, with an accuracy and negative predictive value of 94% and 92%, respectively. PET was false negative in a patient with a slowly growing malignant solitary fibrous tumor and false positive in a patient with infectious pleuritis. Median standardized uptake values calculated for 7 patients with malignant and benign pleural diseases were 6.28 and 1.69, respectively. Patients with a PET score of 1 or 2 survived significantly longer than patients with a PET score of 3 or 4.

Qualitative assessment of pleural thickening with PET accurately discriminates between malignant and benign pleural thickening, with a high accuracy and negative predictive value.