- Background of study: approximately a quarter of the patients who are diagnosed with colorectal cancer and metastases have their metastases in the peritoneum, the so called peritoneal metastases. The vast majority of these patients cannot be cured by surgery, frequently due to too many peritoneal metastases. These incurable patients have a very short life expectancy. Nowadays, they are treated with chemotherapy through the veins. However, chemotherapy through the veins appears to be relatively ineffective against peritoneal metastases, probably because it does not reach the peritoneal metastases very well. Chemotherapy through the veins may also cause side effects that are sometimes severe. Recently, doctors developed PIPAC: a short laparoscopic operation during which chemotherapy is sprayed in the abdomen for 30 minutes, directly against the peritoneal metastases. As a result, PIPAC may be more effective against peritoneal metastases than chemotherapy through the veins. It may also have less side effects, because the chemotherapy mainly stays in the abdomen, not in the veins. PIPAC indeed shows promising results in the first European patients with peritoneal metastases of colorectal cancer who have been treated with this operation.