A multi center clinical trial has been conducted with enrollment of more than 200 patients with colorectal cancer in stage IIb and III. 3D micro-tumors were generated from tissues resected from the patients and screened for efficacy and resistance towards all prevailing standard treatment regimens. The clinical study will be conducted at Bispebjerg Hospital (BBH) in Copenhagen, Denmark and at Universitäts Klinik Eppendorf Hamburg (UKE) in Hamburg, Germany. Treatment response will be evaluated with CT-scans six, twelve and twenty-four months after initiation of chemotherapy. The results of the test will be evaluated by monitoring the Progression-Free-Survival of the individual patients. The results of the present ChemoGuide study will not influence the treatment decision; but will be evaluated for its ability to predict patient outcome. A parallel study will be launched at the Cancer Center at University of Colorado where colorectal tumor tissue from patients is xenograp'ed into immune compromised mice (Patient-Derived-Tumor-Xenografs, PDTX). Tumor tissue from the PDTX mice will be evaluated for its ability to produce 3D micro-tumors.