Clinical relevance of fusion images using 18F-2-fluoro-2-deoxy-D-glucose positron emission tomography in local recurrence of rectal cancer

Local recurrence of rectal cancer is a critical issue. Anatomical images, such as computed tomography (CT) or magnetic resonance imaging (MRI), are sometimes insufficient for preoperative evaluation. A useful modality for diagnosis of local recurrence of rectal cancer is 18F-2-fluoro-2-deoxy-D-glucose positron emission tomography (FDG-PET), but it does not give adequate information about anatomy. To utilize the advantages of these techniques, this study was done to validate the accuracy of using fused images and their usefulness in the decision making for surgical intervention of local recurrence of rectal cancer by directly comparing the fused images with resected specimens. PET and CT/MRI were performed for patients suspected of local recurrence of rectal cancer (n=4). PET image data were re-calculated to fit CT/MRI images and manually superimposed on the anatomical images. Fusion images were compared with resected specimens. Radical operation was carried out for three patients. Fusion images provided information on precise tumor location, and extent of tumor invasion as well as the diagnosis of tumor recurrence. All patients underwent curative operation with negative surgical margins, and the information provided by the fusion images was confirmed by comparison with resected specimens. In all cases, preoperative evaluation of tumor recurrence with fusion images provided more useful clinical information for the management of patients than the anatomical images alone. PET images, when combined with MRI or CT, may prove to be a useful adjunct in the management of patients being evaluated for resection of local recurrence of rectal cancer.