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Clinical Value of Whole Body F-18 FDG PET in The Management of Recurrent Colorectal Malignancy.

PURPOSE
The aim of this study was to evaluate the clinical value of whole body 18F-fluorodeoxyglucose positron emission tomography (FDG-PET) in the patient with a recurrence of a previously treated colorectal malignancy.


MATERIALS AND METHODS
Fifty-eight cases were scanned using PET at the PET Center of Seoul National University Hospital between May 1995 and Aug 2002. All the patients had had a previous operation for a colorectal malignancy. The PET scans were performed for the following reasons: - investigation of a recurrence (n=12), investigation of the operability (n=38) and clinical follow up (n=8). In these 58 cases, 47 of the CT scans and 55 of the CEA (Carcinoembryonic antigen) were checked prior to the FDG- PET. The accuracy, sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) of the PET scans were calculated, and compared with those of conventional CT scan and CEA, which were also compared with the previous reported data. Eight cases, whose managements were influenced by the PET findings, were analyzed.


RESULTS
Recurrences, or metastases, of colorectal cancer developed in 51 cases, with 49 of these being detected by the PET. The accuracy, sensitivity and specificity of the PET were 96.6 (56/58), 96.1 (49/51) and 100% (7/7), respectively. The PPV and NPV of the PET were 100 (49/49) and 77.8% (7/9), respectively. The accuracy and sensitivity of the PET were higher than those of the CT (85.1 and 88.1%), with the differences being statistically significant (p-value 0.001 and 0.003, respectively).


CONCLUSION
It is concluded that a FDG-PET scan is a more accurate and sensitive diagnostic tool than a CT scan for the detection of a recurrence or metastasis in a colorectal malignancy. In addition, a FDG-PET may alter the management of patients with recurrent colorectal cancer. Therefore, it is recommended that a PET should be considered when a tumor recurrence is suspected during conventional follow up.