The metastatic colo-rectal cancer (especially with hepatic metastatic lesions, but also peritoneal or pulmonary lesions) is a major public health issue, because of its frequency, the heavy treatments and the cost of new therapeutic molecules involved, in particular targeted therapies that can result in specific adverse events. The first-line treatment often consists of a polychemotherapy, which can be associated to a targeted therapy. According to the therapeutic response, patient condition and disease extent, some patients may benefit from prognosis-changing treatments such as surgery of metastases. However, the best morphological response is most of time evidenced after only 6 or 8 cycles of treatment, corresponding to 3 to 4 months. Therapeutic evaluation with FDG PET/CT is validated in several neoplasia (lymphoma, breast cancer). Data on FDG PET evaluation of colic cancer chemotherapy are currently insufficient to propose its use in the usual clinical setting. We thus are going to study the performance of early FDG PET therapeutic evaluation to predict response to first-line chemotherapy in patients with potentially resectable metastases. If early PET diagnostic performances prove satisfying, this approach could become of paramount importance to tailor therapeutic strategy for these patients, with the possibility of early modification of chemotherapy protocol, which is now possible thanks to the existence of therapeutic alternatives (chemotherapy intensification, replacement of oxaliptaine by irinotecan or conversely, replacement of an anti-EGFR by an anti-angiogenic or conversely).

Inclusion Criteria:

• Histologically proved colo-rectal cancer
• Measurable metastatic disease according to RECIST 1.1 criteria
• Metastases considered potentially resectable (for example : hepatic, nodular peritoneal, lung lesions…) by the multidisciplinary committee meeting
• ECOG≤2
• Patient candidate to a first-line chemotherapy± targeted therapy according to standard protocols : LV5FU2, FOLFOX, FOLFIRI, FOLFIRINOX +/- bévacizumab, aflibercept , cétuximab, panitumumab
• In case of metachrone metastasis, adjuvant chemotherapy stopped for more than 6 months before relapse diagnosis
• Predictable life expectancy of more than 6 months
• Signed informed consent
• Age > 18 years

Exclusion Criteria:

• Patient with another evolutive neoplastic disease
• Patient participating in another study evaluating an imaging technique using ionizing radiations
• Brain metastasis
• Absence of health insurance coverage
• Pregnant of breastfeeding woman
• Hypersensitivity to FDG or to one of the excipients of used specialty

Population fo patients with metastic colo-rectal cancer eligible to first line chemotherapy