Genetic alterations during treatment of oligometastatic colorectal cancer (GATTACA)

Interventions: Group 1: Patients treated in this study receive a local Therapy (Thermal ablation, Brachytherapy, Mikrowaveablation, stereotactical radiation, surgical resection) after there has been a progress while undergoing Chemotherapy.
The study will only accompany the intended Treatment, but not influence the chosen methods.
During the study additional blood samples will be taken during routine blood draws to examinate whether changes in free floating DNA will occur after local Therapy.
Primary outcome(s): There is a proportionality between the fall of the free-circulating tumor DNA 8 weeks after therapy and 16-72 week interval and the progression free survival and / or overall survival. (Check of the degree of response)
Study Design: Allocation: ; Masking: ; Control: ; Assignment: ; Study design purpose: Prognosis