A dose titration study and a combined superiority registry-based open-label randomized control trial is planned to answer the trial objectives. The study will be registry-based to allow simpler and more comprehensive follow-up. Patients with colorectal cancer will be treated with cytoreductive surgery (CRS) together with either standard oxaliplatin HIPEC (the control for the efficacy study) or oxaliplatin/irinotecan HIPEC in combination with 5-FU 24-hour EPIC. The 5-FU will be administered postoperatively when the abdomen is completely sutured. The drug is divided equally into 2 injections of 200 ml each and injected through two abdominal drains that are clamped for 16 hours. For dose escalation, the titration groups (á 3 or 6 patients) are followed for 30 days postoperatively after which the Data Monitoring Committee (DMC) will determine whether or not to increase the 5-FU dose for the following group of patients. To study efficacy, randomization is performed intraoperatively. The patient is followed up postoperatively for a total of 3 years for the secondary endpoints which may be extended by the study committee to 5 years. Since the trial is registry based, the long-term follow-up does not require separate eCRF evaluations. These evaluations can be automatically retrieved from the registry - both recurrence data, quality of life, and morbidity data. Some specific eCRF evaluations will be integrated as a separate study part of the HIPEC registry, such as inclusion/exclusion criteria and adverse event reporting (including SUSAR reporting).