The use of 18F-FDG PET/CT in colorectal liver metastases-comparison with CT and liver MRI

Purpose We compared 18-fluoro-2-deoxyglucose ((18)FFDG) positron emission tomography-CT (PETCT) with contrast-enhanced whole-body CT (ceCT) in identifying extrahepatic disease and with manganese dipyridoxyl diphosphate (Mn-DPDP) liver MRI for liver metastases in patients with colorectal liver metastases being considered for surgery. Methods Sixty-five patients (median age 65 years; 42 men) with colorectal cancer and known or suspicious liver metastases and who underwent a PETCT, ceCT and Mn-DPDP MRI were identified. Results were retrospectively reviewed for extrahepatic disease on PETCT and ceCT, and for the presence and number of liver metastases on PETCT and Mn-DPDP MRI. Proof of metastases was based on histopathology or clinical/imaging follow-up, demonstrating disease progression or response. Results PETCT identified unexpected extrahepatic disease not detected on ceCT, leading to change in surgical management in 17%. There were three other false-positive cases on PETCT. For liver metastases on a per-patient basis, the sensitivity and specificity of both PETCT and Mn-DPDP MRI were 98% and 100%, respectively. On a per-lesion basis, PETCT and MRI were discordant in 15% (10/66 scans). MRI correctly identified more sub-centimeter metastases in eight scans. PETCT correctly identified more metastases in one case and confirmed disease in one equivocal MRI. Conclusion PETCT has incremental benefit over conventional ceCT in identifying extrahepatic disease in metastatic colorectal cancer. PETCT has high sensitivity and specificity for the presence of liver metastases and should be included early in initial pre-surgical evaluation and could potentially guide the use of Mn-DPDP MRI. However, Mn-DPDP MRI is superior for small liver metastases and remains a prerequisite for surgical planning in patients with confined liver metastases.