The aim of the study is to examine the effects of anemia correction with intravenous administered iron on clinical outcomes and the immune response on the tumor in patients with planned colonic- or rectal cancer surgery.

The study will be performed as a retrospective propensity score-matched cohort study with an examination of immune response in tumor and clinical outcomes, between patients with anemia without correction with iron(III)isomaltoside, non-anemic patients, and anemic patients treated with iron(III)isomaltoside prior to surgery. Propensity score matching will ensure identification of controls from a pool of patients treated at the Department of Surgery, Zealand University Hospital. The two control groups will be: an anemic historical control group (group 1), and a non-anemic concurrent control group (group 2). Group 3 will be the treatment group, with patients with anemia and treated with iron(III)isomaltoside.

The study period of cases undergoing i.v. treatment will be 1st of February 2017 to 31st of October 2019 with approximately 70 cases included

Inclusion Criteria:

• Undergoing curative intended surgery for colon or rectum cancer
• UICC stage I-III

Exclusion Criteria:

• Neoadjuvant oncological treatment
• Acute / subacute surgery
• Palliative surgery
• Other pathology than adenocarcinoma