Liquid biopsies in patients with peritoneal metastases of colorectal cancer.

Interventions: This is an observational cohort study to assess the correlation between ctDNA and cytoreductive surgery. No interventions are performed. Treatment and follow-up of patients will not be influenced by ctDNA results. Two additional viles of blood (2*9mL Streck) are taken before (on the day of HIPEC surgery) and after cytoreductive surgery and HIPEC (2-4 weeks after HIPEC surgery). Primary outcome(s): Plasma levels of ctDNA preoperatively. Study Design: N/A: single arm study, Single blinded (masking used), N/A , unknown, Other