A register-based study is conducted to examine clinical outcomes following a population-based, multi-centred implementation of Laparoscopic Complete Mesocolic Excision (LCME) in the Central Denmark Region, Denmark.

This study was conducted as a population-based "before-and-after" cohort study following the implementation of LCME in the Central Denmark Region (CDR), Denmark, in 2017. The IDEAL framework (Idea, Development, Evaluation, Assessment, Long-term) was used for examining the outcome of a training program on the LCME adoption.

Training programme A LCME training program was conducted from March 2017 to October 2017 in the CDR, inspired by the National English Laparoscopic Colorectal Surgery Course.

Patients This study included all colon cancer patients undergoing a curative-intent bowel resection in the defined timeframe. Exclusion criteria comprised: 1) another synchronous colon cancer; 2) metastatic disease at the time of surgery; 3) non-curative procedures or local resections only; 4) Danish residency <10 years preoperatively; and 5) non-colon primary cancer.

Data sources The DCCG database, a national registry of newly diagnosed colon cancer patients, was used to identify the primary cohort. For follow-up data beyond 30 days after surgery, the cohort was linked to the following registries: 1) the Danish Civil Registration System (DCRS), 2) the Danish Cancer Registry (DCR), 3) the Danish National Patient Registry (DNPR), 4) the Danish Pathology Registry (DPR) and the Danish Pathological Data Bank (DPDB).

Outcome The primary outcome was the cumulative incidence of colon cancer recurrence 5 years after surgery. A validated algorithm was used to identify recurrence.

The secondary outcome was postoperative complications within 30 days graded by the Clavien- Dindo Classification (CDC) (minor: I-II, major: III-V).

Inclusion Criteria:

• newly diagnosed colon cancer patients.

Exclusion Criteria:

1. another synchronous colon cancer
2. metastatic disease at the time of surgery
3. non-curative procedures or local resections only
4. Danish residency <10 years preoperatively
5. non-colon primary cancer.

This study included all colon cancer patients undergoing a curative-intent bowel resection in Central Denmark Region, Denmark in the following timeframe: (January 1, 2015-December 31, 2016) and (January 1, 2018-December 31, 2019).

IPD will not be shared as this is a register-based study, and according to the GLPR and Danish law, the IPD date cannot be shared.