FDG PET/CT in the detection of recurrent rectal cancer

The purpose of this study was to assess the additional value of combined fluorine 18 (18F)-fluorodeoxyglucose (FDG) positron emission tomography (PET)/computed tomography (CT) in the follow-up of rectal cancer after surgery. Forty-eight examinations in 30 patients were evaluated retrospectively. CT and PET components were interpreted separately, and this was followed by a consensus reading. Sites of increased FDG uptake as well as PET/CT findings were categorized as benign (1), equivocal (2), or malignant (3). The standard of reference was histology or clinical and imaging follow-up for at least 6 months. Sensitivity, specificity, positive and negative predictive values, and accuracy for differentiating benign (14/31) from malignant (17/31) uptake sites in the small pelvis were 100%, 64%, 77%, 100%, and 84% for PET/CT, and 100%, 29%, 63%, 100%, and 68% for PET, respectively. Regarding extrapelvic abnormalities, PET/CT was able to distinguish benign (31/88) from malignant (57/88) with a sensitivity, specificity, positive and negative predictive values, and accuracy of 100%, 87%, 93%, 100%, and 95%, compared with 96%, 68%, 85%, 91%, and 86% for PET. The rare case of an FDG uptake of adrenal adenoma is documented. PET/CT is valuable in the staging of rectal cancer, particularly for excluding recurrent disease suspected by PET interpretation alone in a considerable number of patients.