Positron Emission Tomography (PET) is a nuclear medicine imaging technique that produces three-dimensional pictures of functional processes in the body. When combined with computed tomography (CT), which uses x-rays and a computer to produce cross-sectional images, PET can give clinicians a more complete picture of cancer growth and stage.
To determine the value of PET/CT in the staging of mesothelioma, the Swiss team analyzed the cases of 62 pleural mesothelioma patients who were undergoing chemotherapy prior to a planned surgery. Since the goal of this induction chemotherapy is to shrink tumors to improve surgical outcomes, accurate staging is especially important.
All of the 62 mesothelioma patients included in the study underwent CT scans. Twenty-eight of the patients also had PET/CT. All of the patients then underwent a radical lung-removing mesothelioma surgical procedure called extrapleural pneumonectomy (EPP) and the stage of their cancer was determined both clinically and pathologically (by looking at the cells under a microscope). The researchers used the information to determine overestimation and underestimation of mesothelioma stage by the two imaging modalities.
Both PET/CT and CT underestimated the size and extent of primary mesothelioma tumors in about 30 percent of cases, although PET/CT was slightly more accurate for tumor extent. The accuracy for determining the spread of cancer to nearby lymph nodes was higher for CT than for PET/CT. Just as importantly, the variability between people reading the results of these scans was lower for PET/CT than it was for CT both for tumor size and for nodal staging.
Study author Thomas Frauenfelder and colleagues conclude that PET/CT is probably better for staging mesothelioma than CT alone, but say better approaches are still needed. “PET/CT underestimated tumor stage in a substantial numbers of cases, showing the need for a more accurate imaging technology or approach,” Frauenfelder writes. The new study appears in the Journal of Computer Assisted Tomography.
Frauenfelder, T, et al, “Use of Computed Tomography and Positron Emission Tomography/Computed Tomography for Staging of Local Extent in Patients with Malignant Pleural Mesothelioma”, October 28, 2014, Journal of Computer Assisted Tomography, Epub ahead of print