Gut Microbiome Dynamics in Metastasized or Irresectable Colorectal Cancer

patients will collect fecal samples at home prior to treatment and at 3 months after start of treatment at the time of response evaluation using a standard stool-collection-kit.

At the day of stool sampling, patients fill out a brief questionnaire about established factors that can change the microbiome such concurrent use of antibiotics and proton pump inhibitors.

4 tubes of blood are collected prior to treatment and at 3 months after start of treatment at the time of response evaluation and sent to the UMCG for storage.