Imaging in pleural mesothelioma: a review of imaging research presented at the 9th International Meeting of the International Mesothelioma Interest Group.

Imaging of malignant pleural mesothelioma (MPM) poses many challenges for imaging specialists and clinicians due to the anatomic location and unique growth pattern of this tumor. Nevertheless, imaging in MPM plays a critical role in diagnosis, prognostication, prediction or measurement of response to therapy, and monitoring of disease recurrence after aggressive surgical management. Imaging-based studies presented at the 9th International Conference of the International Mesothelioma Interest Group (IMIG) in October 2008 sought to further define the current practice and future potential of imaging for the mesothelioma patient. The Imaging Session was dominated by presentations that addressed the use of fluorodeoxyglucose positron emission tomography (FDG-PET), a clear indication of the expanding role of this modality. These uses included FDG-PET imaging at the point of diagnosis, in prognostication, and in the assessment of response to chemotherapy. Often FDG-PET studies were combined with computed tomography (CT) scans in an attempt to overcome limitations associated with either imaging modality alone. At diagnosis, FDG-PET parameters had a high sensitivity and specificity for differentiation of benign from malignant pleural disease. The use of FDG-PET to extract quantitative features from metabolically active tumor volume was shown to be a significant factor in the prediction of patient survival. The prognostic value of FDG-PET was not confounded by prior talc pleurodesis, despite the inflammatory response associated with the procedure. Metabolic response based on FDG-PET was found to be significantly correlated with progression-free survival. CT-based assessment of mesothelioma was determined to be inconsistent with spherical-model-based criteria so that changes in tumor area, a presumably more complete assessment of tumor burden, exhibited a 46% concordance rate with changes in linear measurements.