The aim of the study was to evaluate the feasibility of TS determination in a multicenter trial setting using a central facility for measurement and confirm its role as predictive factor for 5-FU treatment in MCRC.

Eligible were patients with non-resectable metastasized or recurrent histologically proven CRC with the presence of a reference lesion two-dimensional measurable and accessible for a biopsy.The biopsy was taken from the reference lesion either by surgery during primary tumor resection, by trans-cutaneous true-cut needle biopsy or by trans-anal approach. Intratumoral relative TS mRNA expression levels were determined using samples shipped in RNA-preserving solution or as glass slides after microdissection of tumor cells. An independent company stratified the patients according to ther relative TS mRNA expression level in TS low and TS high followed by randomization to receive either FUFA of Folfiri. Response to chemotherapy was evaluated and documented according to the RECIST criteria after every therapy cycle.

Inclusion Criteria:

• patients (>= 18 years) with non-resectable metastasized or recurrent histologically proven CRC with the presence of a reference lesion two-dimensional measurable and accessible for a biopsy
• a performance status WHO 0-2 (Karnofsky >= 60%)
• an estimated life expectancy of at least 3 months
• written informed consent

Exclusion Criteria:

• patients older than 75 years not fulfilling these criteria
• brain metastases or a secondary cane
• a history of a systemic palliative chemotherapy
• and an adjuvant chemotherapy (within 6 months)
• pregnant or nursing women
• a known allergy toward irinotecanhydroclorid or of any ingredients of Campto or other severe medical
• laboratory and social conditions not allowing chemotherapy and follow-up