The purpose of the study is to determine if short-term outcomes of colon resections after full bowel preparation (mechanical bowel preparation plus oral antibiotics) are superior to colon resections with no bowel preparation.

The design involves random allocation of eligible patients to full bowel preparation or no bowel preparation in 1:1 ratio. After that colon resection is performed in both groups.

Short-term outcomes are assessed in 30 day period after surgery. This is a superiority trial evaluating statistical superiority. Rate of anastomotic leak is anticipated to decrease from 8% (data from local registry) to 3%. For power of 80% enrolment of 586 patients is required.

The intent-to-treat principle is used for the data analysis.

Inclusion Criteria:

• histologically confirmed adenocarcinoma of the colon (caecum, ascending, transverse, descending, sigmoid)
• clinical stage T1-4aN0-2M0-1 (distant metastases must be resectable)
• indications for surgical colonic resection
• ECOG status 0-2
• At least 18 years of age
• Written informed consent

Exclusion Criteria:

• Medical or psychiatric conditions that compromise the patient's ability to give informed consent or comply with the study protocol
• Pregnancy or breast feeding
• Medical contraindications for surgical treatment
• Any use of antibiotics 30 days prior to inclusion
• Functioning stoma
• Contraindications for use of MBP or OA drugs or their components
• Indications for mandatory MBP (planned intraoperative colonoscopy etc)
• Indications for obstructive resection
• Acute bowel obstruction, bleeding or perforation
• Other malignancies not in remission

We are not planning to share individual participant data