Assessment of local control after laser-induced thermotherapy of liver metastases from colorectal cancer:: Contribution of FDG-PET in patients with clinical suspicion of progressive disease

Background: Management of patients after locally ablative treatment of liver metastases requires exact information about local control and systemic disease status. To fulfill these requirements, whole-body imaging using positron emission tomography with F-18-fluorodeoxyglucose ( FDG-PET) is a promising alternative to morphologic imaging modalities such as computed tomography ( CT) and magnetic resonance imaging ( MRI). Purpose: To evaluate FDG-PET for the assessment of local control and systemic disease in patients with clinical suspicion of tumor progression after laser-induced thermotherapy ( LITT) of colorectal liver metastases. Material and Methods: In 21 patients with suspicion of progressive disease after LITT, whole-body FDG-PET was performed. The presence of viable tumor within treated lesions, new liver metastases, and extrahepatic disease was evaluated visually and semiquantitatively ( maximal standard uptake value [ SUVmax], tumor-to-normal ratio [ T/N]). The standard of reference was histopathology ( n=25 lesions) and/or clinical follow-up ( >12 months) including contrast-enhanced MRI of the liver. Results: Among 54 metastases treated with LITT, 29 had residual tumor. Receiver operating characteristic ( ROC) analysis of SUVmax ( area under the curve ( AUC) 0.990) and T/N ( AUC 0.968) showed a significant discrimination level of negative or positive lesion status with an equal accuracy of 94% ( 51/54). The overall accuracy of visual FDG-PET was 96% ( 52/ 54), with one false-negative lesion among six examined within 3 days after LITT, and one false-positive lesion examined 54 days after LITT. In the detection of new intra- and extrahepatic lesions, FDG-PET resulted in correct alteration of treatment strategy in 43% of patients ( P=0.007). Conclusion: FDG-PET is a promising tool for the assessment of local control and whole-body restaging in patients with clinical suspicion of tumor progression after locally ablative treatment of colorectal liver metastases with LITT.