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 F-18-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 F-18-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, F-18-FDG-PET clarified otherwise unclear local recurrences. In five patients, F-18-FDG-PET showed pulmonary metastases that had previously been unknown. In a total of 16 patients (20.8%), F-18-FDG-PET provided additional information leading to a change of the treatment strategy. F-18-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.