Recurrence of colorectal cancer after apparently curative resection remains common, with reported relapse rates of up to 40%. Because complete resection of solitary metastases of local recurrence may improve long-term survival, surgical
management
of
such cases has become increasingly aggressive but has led to only modest survival benefit. The limitations of current approaches based on structural imaging are well documented, with over half of the patients who are thought suitable for curative
surgery being found to have unresectable disease at operation. Therefore, better preoperatine assessment is crucial. The increasing use of FDG-PET as an oncologic staging investigation has significantly improved the assessment of patients with
suspected
colorectal cancer recurrence. Several studies show that substantial and largely appropriate changes in patient management occur, often sparing patients the significant morbidity and mortality associated with aggressive but futile therapies while
also
saving scarce community resources. Nevertheless, the clinical relevance of these findings has still been questioned. The utility of PET in routine clinical practice will likely depend on its ability to provide incremental information compared
with
CT in
selected patients rather than to serve as a replacement for CT. In conclusion, in patients with suspected recurrent or matastatic colorectal carcinoma, FDG-PET should be performed (1) when there is rising carcinoembryocin antigen levels in the
absence
of a known source, (2) to increase the specificity of structural imaging when there is an wquivocal lesion, and (3) as a sceening method for the entire body in the preoperative staging before curative resection fo recurrent disease.
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