Adenocarcinoma of the colon and rectum is a common, serious disease and it is the second cause of death from cancer in Spain.

The prognosis of CRC depends to a great extent on its stage when diagnosed. Patients with advanced disease, who present up to 40% of all patients, have a poor prognosis. Although the application of modern chemotherapy and radiotherapy treatments obtains median survival periods of around 24 months, the proportion of patients with advanced disease who obtain a cure is low.

Systemic treatment of advanced CRC has changed considerably in the last ten years with the introduction of active drugs such as oxaliplatin, irinotecan, and capecitabine. The most commonly used first line regimens are 5-Fluorouracil-Leucovorin-Oxaliplatin (FOLFOX), Capecitabine-Oxaliplatin (XELOX), 5-Fluorouracil-Leucovorin-Irinotecan (FOLFIRI) and, to a lesser extent, Capecitabine-Irinotecan (XELIRI). Chemotherapy regimens are combined with different agents against therapeutic targets, three of which are effective in colon cancer: bevacizumab, which targets vascular endothelial growth factor (VEGF) and cetuximab or panitumumab, which target the epidermal growth factor receptor (EGFR).

The use of cetuximab and panitumumab is not recommended in patients with KRAS mutations and the combination of a VEGF and EGFR agents is not beneficial.

Two recent studies results have identified KRAS mutations as frequent drivers of acquired resistance to cetuximab and panitumumab in colorectal cancer patients. The conclusions indicate that the emergence of KRAS mutant clones can be detected non-invasively months before radiographic progression by a DNA Blood Test (Inostics´BEAMing Technology).

Centro Integral Oncológico Clara Campal (CIOCC) is aiming to undertake a pioneer project aimed at integrating the analysis of KRAS switch status by BEAMing Technology in patients with metastatic colorectal cancer, tumor KRAS wild-type and BEAMing wild-type treated with first line FOLFIRI-cetuximab

In naive chemotherapy tumor-KRAS wild-type metastatic colorectal cancer patients, who are BEAMing positive (KRAS mutated in blood) before treatment may have worse evolution in terms of PFS (progression Free Survival) and response rate than BEAMing negative (KRAS native in blood) patients.

To know the proportion of patients who are BEAMing positive (KRAS mutation can be detected in circulating extracellular DNA) at the beginning of treatment, could be of great importance for treatment efficacy.

Inclusion Criteria:

• Diagnosis of stage IV colorectal adenocarcinoma.
• Patient ≥ 18 years of age.
• ECOG PS 0-1
• Life expectancy ≥ 6 months
• Candidate for first-line systemic chemotherapy according to regular clinical practice.
• Measurable disease.
• Wild-type KRAS
• Signed informed consent form.

Exclusion Criteria:

• Patient who has received prior chemotherapy for metastatic CRC, except for adjuvant treatment completed at least six months before entering study.
• Patient in whom there is a contraindication for the use of any of the drugs used in first-line treatment of colorectal cancer: 5-fluorouracil,, irinotecan or cetuximab

Patients with metastatic colorectal cáncer and wild-type KRAS treated with Folfiri-Cetuximab as first-line treatment.