Currently, there is a lack of knowledge on the effect of additional flushing after HIPEC on tumour platinum exposure, systemic platinum exposure and platinum concentration in drain exudate and thereby personal exposure. Therefore the investigators want to perform a study to investigate the effect of flushing after HIPEC on tumour exposure, systemic exposure and on wound exudate concentration.

Cytoreductive surgery combined with hyperthermic intraperitoneal chemotherapy (HIPEC) is standard care in the treatment of patients with peritoneal carcinomatosis as a result of intra-abdominal cancers. In many (inter)national centres oxaliplatin is used for the primary HIPEC treatment. Although the oxaliplatin dose of 460mg/m2 is widely accepted, the exact procedure of HIPEC differs between institutions and surgeons. Due to a great variety in the volume of the abdominal cavity, platinum concentration in the perfusate might differ between patients. Moreover, there is no consensus about the usefulness of flushing the HIPEC system with crystalloids at the end of oxaliplatin administration. Flushing is predominantly performed with the idea to minimize both systemic exposure of ultrafilterable platinum and personnel exposure to platinum contaminated exudate. On the other hand, HIPEC without flushing might increase effectiveness because intraperitoneal tumour cells are exposed to high concentrations of oxaliplatin for a longer time period. The option of flushing is based on an individual preference of the surgeon. Currently, there is a lack of knowledge on the effect of flushing on tumour platinum exposure, systemic platinum exposure and platinum concentration in drain exudate and thereby personal exposure. Therefore the investigators want to perform a study to investigate the effect of flushing after HIPEC on tumour exposure, systemic exposure and on wound exudate concentration.

Inclusion Criteria:

1. Subjects must provide written informed consent prior to performance of study-specific procedures or assessments and must be willing to comply with treatment and follow-up.

   Note: Informed consent may be obtained prior to start of the specified screening window.

   Note: Procedures conducted as part of the subject's routine clinical management (e.g., blood count, imaging study) and obtained prior to signing of informed consent may be utilized for screening or baseline purposes.

2. Age ≥ 18 years

3. Confirmed diagnosis of preoperatively identifi ed primary or recurrent peritoneal carcinomatosis (PC) of colorectal origin who are planned for HIPEC treatment with oxaliplatin according to routine clinical care

Exclusion Criteria:

1) Patients who do not achieve a cytoreduction score of CC-0 will be excluded from the study.

Patients diagnosed with peritoneal carcinomatosis who undergo HIPEC treatment with oxaliplatin as part of routine care.