The aim of the study is to obtain information on FLT used in a PET-scan as a marker for the proliferation of colorectal livermetastases, so that the risc of recurrence can be identified in a noninvasive way, concerning patients with resectable colorectal livermetastases.

The hypothesis of this study is that a higher uptake of FLT in the livermetastases has a good correlation with the proliferation rate of the metastases. This rate is related to the risc of recurrence.

Aim of the study:

Validation of FLT-PET as a proliferationmarker for colorectal livermeastases, so that the risc of recurrence in patients with resected colorectal livermetastases can be assessed in a noninvasive method.

Studydesign:

Validationstudy (n=40) to determine the correlation between kwantitative FLT-PET (in this study determined before resection of the colorectal livermetastases) and the hitological detrmined proliferation index in the resected specimen of the metastases (''''golden standard''''). If correlation is established, the correlation between the proliferation and recurence rate is studied also (n=80).

Studypopulation:

Patients with colorectal livermetastases.

Intervention:

FLT-PET sscan

Scientific basis of study:

Several reports show that presence or absence of extrahepatic disease is a determining prognostic factor. Patients with extrahepatic disease are rarely suited for resction of the livermetasases. Recently several papers describe dat the proliferation index of the livermetastasis is another determining prognostic factor. Patients with a high proliferation factor have a worse prognosis. For both of these determining factors, it seems that PET diagnostics play an essentail role and contribute to beter selection of patients suitable for resection.

Diagnostics on proliferation:

Seeing that the proliferation rate is preoperatively not determined without a biopsie (which is contraindicated due to dissemination), all patients with colorectal livermetastases (with no signs of extrahepatic deposits) are resected, without knowledge of the proliferation. FLT is a marker that visualizes prolifaration and thus seems an ideal candidate to determin the proliferation rate in a noninvase method. As of yet no validationstudies of FLT-PET in colorectal livermetastases have been described.

Evaluation:

Quantative histologic data are correlated with the quantitative FLT-PET data. If the correlation is higher that 0.85, this correlation is established. If this correlation is found, the inlcusion of patienst will be extended from 40 to 80 patients, seeing that this will give us teh opportunity to correlate clinical data with the histological data. (alpha = 0.05, one-sided, beta = 0.90, assuming that an acceptable difference in sensitivity between both tests is 0 and an unacceptable difference is 0.02). If this correlation is significant, a new suty will be proposed with the introduction of neoadjuvant chemotherapy, where the selection will determined on basis of the proliferation rate.

Inclusion Criteria:

• colorectal livermetastases deemed resectabel on three-fase CT-scan of the liver
• no evidence of extrahepatic disease on CT chest and abdomen and possible FDG-PET (if part of surgical work-up)
• no evidence of local recurrence or second primary colorectal tumor on colonoscopy or colonography
• primary colorectal tumor radically removed
• informed consent

Exclusion Criteria:

• pregnancy
• recent chemotherapy