Impact of 18F-FDG-positron emission tomography for decision making in colorectal cancer recurrences.

Diagnostic imaging for suspected tumour recurrence of primary colorectal cancer frequently lacks specificity and sensitivity. The impact of whole body 18F-FDG-positron-emission tomography (PET) on detection of local recurrences and hepatic or pulmonary metastases was evaluated in a prospective study. Results were compared with computed tomography (CT), ultrasonography, magnetic resonance imaging and conventional chest X-ray. The study included 71 patients (77 investigations) with suspected local recurrence, hepatic metastases or unexplained raised level of the tumour marker carcinoembryonic antigen (CEA). The results demonstrate that 18F-FDG-PET was clearly superior to CT with regard to detection of hepatic metastases. Sensitivity was 1.0 and specificity 0.98 compared with 0.87 and 0.91 for CT. In four cases, 18F-FDG-PET clarified otherwise unclear local recurrences. In five patients, 18F-FDG-PET showed pulmonary metastases that had previously been unknown. In a total of 16 patients (20.8%), 18F-FDG-PET provided additional information leading to a change of the treatment strategy. 18F-FDG-PET clearly has the ability to detect colorectal tumour recurrence and its metastases in a whole body format. Therefore, it may be applied in the follow-up of patients with primary colorectal cancer. Despite the costs, it is certainly recommended for patients with an otherwise unclear increase of CEA level or with unproven local recurrence.