 The basic assumption for this study is that the experimental diagnostic strategy based on CT FDG-PET compared to the conventional diagnostic strategy based on CT leads to a more accurate diagnosis about operability of liver metastases. Therefore, the economic evaluation is based on the principles of a cost-effectiveness analysis. Using a differential approach, patients are followed up for a period of 9 months. In addition, patients suffering from recurrence of the disease will be followed during this period in order to be able to evaluate the total costs involved in the care of these patients. Because of the specific patient population in this study, non-medical costs are expected not to be different between the patient groups. Therefore, a health care perspective is the basis for the analyses, indicating that only health care costs are subject to study. A problem with basing cost estimates on data gathered as part of a clinical trial is the extent to which one is capturing resource use associated with the trial per se i.e. costs of doing scientific research rather than the costs of providing the diagnostic and therapeutic care Drummond 1997. These so called protocol driven costs will be excluded from the cost analyses. Regarding the cost-effectiveness analysis, for each patient the total costs will be split into diagnostic and therapeutic costs. Focusing on the effectiveness measure proportion of accurate diagnoses, only the diagnostic costs will be used to calculate the incremental ratio comparing the FDG-PET strategy versus the conventional strategy. This results in an estimate of the additional diagnostic costs per extra accurate diagnosis. Concerning the effectiveness measure proportion of patients with disease-free survival, the total costs until recurrence of the disease or to the end of follow up will be related to the mean time of disease free survival. This results in an estimate of the additional medical costs per month of disease free survival. In addition, a cost-utility analysis CUA will be carried out to incorporate the preferences of the participants considering their own health status at the start of the treatment and after follow-up. Based on these preferences combined with life expectancy figures, calculation of so-called quality-adjusted life years QALYs is applicable. A general measure to express the benefits for the two different treatment strategies will be calculated by computing the area under the curve of the utility x measurement moment from baseline through the assessment at month 9 curve. These QALYs for the 9-month period can be combined with the costs of each strategy to arrive at the cost per QALY gained. 