The aim of the study is to evaluate whether the preoperative level of myeloid-derived suppressor cells is associated with postoperative complications classified by Clavien-Dindo categories. Levels of all MDSC, polymorphonuclear MDSC (PMNMDSC), monocytic MDSC (MMDSC), early-stage MDSC (EMDSC) and monocytic to polymorphonuclear MDSC ratio (M/PMN MDCS) were established and compared in patients with postoperative complications, severe postoperative complications (>= IIIA according to Clavien-Dindo) and severe septic complications.

Levels of all MDSC, polymorphonuclear MDSC (PMNMDSC), monocytic MDSC (MMDSC), early-stage MDSC (EMDSC) and monocytic to polymorphonuclear MDSC ratio (M/PMN MDCS) were established and compared in patients with and without postoperative complications. Then subgroup analysis was performed to compare levels of MDSC in patients with severe postoperative complications (>= IIIA according to Clavien-Dindo) and those without severe complications. Another subgroup analysis will be performed for patients with severe septic complications that are defined as severe complications with accompanying infection. Levels of MDSC will be compared by means of U Mann Whitney test as their distribution is not normal. After above mentioned analyses it will be possible to evaluate the role of MDSC in patients with colorectal cancer in terms of postoperative complications. Additional analyse will be performed to compare levels of MDSC in patients who underwent neoadjuvant treatment (radiotherapy or chemoradiotherapy).

Inclusion Criteria:

• age ≥ 18
• colorectal cancer confirmed by histological examination of biopsy specimen
• elective operation
• signed informed consent

Exclusion Criteria:

• Age < 18
• Pregnancy or lactation
• Emergency operation
• General condition that precludes understanding and signing of the informed consent form

Patients with histologically-confirmed colorectal cancer who undergo elective surgery.