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.

Advantages and limitations of FDG PET in the follow-up of breast cancer.

18F-Fluoro-2-deoxy-D-glucose positron emission tomography (FDG PET) has been evaluated in breast cancer for the characterisation of primary tumours, lymph node staging and the follow-up of patients after surgery, chemotherapy and/or external radiotherapy. In contrast to both the low sensitivity and moderate specificity of FDG PET in the initial detection and characterisation of breast cancer and the low lesion-based sensitivity for lymph node staging, the results from use of FDG PET in re-staging breast cancer patients are very promising. A major advantage of FDG PET imaging compared with conventional imaging is that it screens the entire patient for local recurrence, lymph node metastases and distant metastases during a single whole-body examination using a single injection of activity, with a reported average sensitivity and specificity of 96% and 77%, respectively. In most studies the sensitivity of FDG PET is higher than that of a combination of conventional imaging methods. Limitations of FDG PET in the follow-up of breast cancer patients include the relatively low detection rate of bone metastases, especially in case of the sclerotic subtype, and the relatively high rate of false positive results. The rather low specificity of FDG PET can be improved/increased by utilising combined anatomical-molecular imaging techniques, such as a PET/CT tomograph. First results using PET/CT imaging in the follow-up of breast cancer patients demonstrate increased specificity compared with FDG PET alone. Both imaging modalities, however, offer to detect recurrent and metastatic breast cancer disease at an early stage and thus continue to demonstrate the efficacy of molecular imaging in patient management, despite the limited therapeutic options in recurrent and metastatic breast cancer.