[The role of positron emission tomography (PET) in the detection of local recurrence and metastases of colorectal cancer].
We presented here the results of PET imaging of 12 patients, previously operated on for colorectal cancer and followed at the 1st Department of Surgery, University of Debrecen. The tests were carried out using 0.15 mCi/kg FDG injections. Whole body imaging was performed in eleven patients. The indication for PET was elevated tumor marker levels in three patients, although CT scan was negative. The PET scan showed lymph node, hepatic and disseminated lymph node metastases with liver involvement in these patients. Suspicious lesions were found on CT scan in the pelvis of four patients. Local recurrence was identified in three of them, PET was negative in the fourth case. Bone scan suggested rib metastasis in one patient, which was not supported at PET investigation. In one patient, the malignant nature of large retroperitoneal lymph nodes could not be determined by CT. PET imaging proved that they were malignant and detected a previously unknown pulmonary metastasis at the same time. In one patient both pulmonary and liver metastases were seen on CT, whereas PET confirmed only the latter. Similarly, CT failed to identify liver metastasis detected at ultrasound, while PET proved it. Finally, a pulmonary metastasis detected on X-ray, could be confirmed by PET only. Based on our experience, we recommend PET-scanning with FDG when conventional imaging is equivocal and/or elevated tumor marker levels are present during follow-up. FDG-PET is important in the detection of local recurrence and metastases as well. It is advisable to use PET more often in the evaluation of patients with recurrent colorectal cancer in order to diagnose recurrences in earlier stages, which helps to identify patients who will benefit from surgery.