The primary focus in this study is to investigate and improve the surgical technique. In addition the collection of clinical data during diagnostic and follow up and the collection of tumor and blood gives us the opportunity to investigate tumor biology and its relevance in terms of determine appropriate treatment strategy both surgically and oncological and to assess and predict treatment outcome.

The aim of this study is to compare short and long-term outcomes between open D3 and laparoscopic CME (complete mesocolic excision) with CVL (central vascular ligation) right colectomy for right-sided colon cancer. Our primary hypothesis is that laparoscopic surgery improves quality of life by reducing pain, postoperative complications and thereby reduces hospital stay and convalescence. On the other hand it is to prove non-inferiority of the laparoscopic group compared to the open group by means of oncological outcome (survival, recurrence). Secondary aim is to evaluate surgical quality by comparing actual vascular stump length between the two groups by postoperative CT and compare number of lymph nodes removed with the specimen. With the use of liquid biopsy we want to detect circulating tumor DNA (ctDNA) and circulating tumor cells (CTCs) and evaluate their value as tumor markers by comparing the prognostic and predictive value. The hypothesis is that ctDNA and CTCs are more sensitive than standard parameters and imaging (CT CEA).

This is a prospective, randomized, multi-center clinical study. The short term outcome, 2 and 5 year survival and mortality rates will be compared between the groups operated with open D3 resection at Haukeland University hospital and laparoscopic CME with CVL right hemicolectomy at Haraldsplass Deaconess hospital. Computer generated block randomization will be used.

All patients ≤ 85 years with tumor localized in the right colon will be considered to participate in the study. The patients will be summoned to the first consultation to the hospital they are referred to. They will be informed of the study. A patient who meets the inclusion criteria will be asked to participate in the study and sign the informed consent. A patient who accepts will be assigned a sequential participant number and then referred to open D3 or laparoscopic CME (right hemicolectomy) according to a pre-specified randomized list of treatments.

All patients referred with right sided colon cancer in the inclusion period will be registered, and the reason why some do not participate in the study will be documented. Patients who decline to participate in the study will be assigned standard treatment in the institution they are referred to.

Blood samples for analysis of ctDNA/CTCs will be collected preoperatively, 3-10th postoperative day, at 3 months and at each check the next five years at six months intervals. All sample times except the first postoperative control, correspond to the time of CEA and CT in ordinary follow-up. Proteomic technology based analysis of tumor tissue

Inclusion Criteria:

• • Patients with malignant tumor of the right colon (cecum, ascending colon, right flexure and right transverse) at CT, colonoscopy.

  • Patients medically cleared by anesthesiologist for general anesthesia and oncological radical resection
  • Patients ≤ 85 years
  • Signed informed consent form

Exclusion Criteria:

• • Patients with recurrent cancer after previous surgery

  • Patients with synchronous distant metastasis
  • Patients with ongoing oncological treatment due to other cancer