In the assessment of CLM, the use of PET has been shown to be both sensitive (96.0%) and specific (97.1%). However, principal investigator Irving Taylor, MD, FRCS, professor of surgery, department of surgery, Royal Free and University College Medical School, London, UK, said, it is now recognised that use of PET alone has limitations for determination of the exact anatomical localisation of liver metastases.

A dual modality PET plus CT (PET/CT) scanner can provide accurate co-registration for a biological assessment with PET scanning and an anatomical assessment with CT scanning, Dr. Taylor said.

"We have investigated the role of PET/CT to determine whether or not it will be in a position to alter the management of our patients with colorectal liver metastases," and thus to provide further patient benefit over routine MDCT alone, he noted in a presentation on November 30^th.

The eligibility criteria were for consecutive patients with suspected CLM who underwent routine imaging with contrast-enhanced MDCT of the thorax, abdomen and pelvis, and whole-body PET/CT scanning, within 2 weeks of each other.

Imaging results were compared on both a patient-by-patient and lesion-by-lesion basis, in terms of concordance/ discordance in detection of the extent of hepatic/ extra-hepatic disease and their subsequence influence on final management. They were further compared with the final diagnosis that included histological, surgical and radiological follow-up.

Of the 32 patients included in the analysis (median age, 63 years; male, 62.5%), the indications for PET/CT imaging were indeterminate lesions found on MDCT scanning (7 patients; 22%) and further assessment of disease burden (25 patients; 78%).

On a lesion-by-lesion basis with the total of 87 lesions detected, the standard MDCT sensitivity of 72% and accuracy of 63% were improved with the PET/CT combination to 90% and 76%, respectively.

"But the important thing," stressed Prof Taylor, "is the overall accuracy, which on this lesion-by-lesion basis was higher with PET/CT compared to CT alone [89% vs 71%]."

Discordant findings were present in 54% of patients, with PET/CT providing additional information in 43%. This included exclusion of hepatic disease in 9% of patients, detection of additional liver metastases missed by MDCT in 9%, and detection of occult extra-hepatic disease in 25% of patients.

However, 9% of patients had discordant findings that were due to incorrect PET/CT findings, Dr. Taylor noted. These comprised 2 false negative liver lesions that were less than 1 cm in size and 1 false positive mediastinal lymph node (tuberculous granuloma).

This combined approach with PET/CT thus provided additional information over standard MDCT in 43% of patients, which translated into changes in management among 34% of patients, with upstaging in 24% and downstaging in 9%. In the remaining 9% of patients, the detection of additional metastatic lesions did not change their management.

Thus, as well as providing additional information in some 40% of cases with PET/CT over standard MDCT, Dr. Taylor finally stressed, "Probably more importantly, in about a third of patients, the PET/CT scan can alter overall management, and determine a more effective form of treatment in these patients with colorectal liver metastases."


[Presentation title: Does [18F]-FDG PET/CT Alter the Management of Patients With Colorectal Liver Metastases? Abstract 015]

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