Table 1. Summary of current clinical practice guidelines on the principals for surgical management of primary and metastatic colorectal cancer.

Guideline	Primary colorectal caner	Metastatic colorectal caner
Japanese Society for Cancer of the Colon and Rectum guidelines 2019 (10)	The extent of lymph node dissection is determined based on the preoperative clinical findings and on the extent of lymph node metastasis and depth of tumor invasion. The extent of the pericolic/perirectal lymph node in colon cancer is defined by the positional relationship between the primary tumor and the feeding artery. Metastasis of the pericolic/perirectal lymph node at a distance of 10 cm or more from the tumor edge is rare.	If both the distant metastases and the primary tumor are resectable, curative resection of the primary tumor performed, and resection of the distant me-tastases is considered. If the distant metastases are resectable but the primary tumor is unresectable, in principle, resection of the primary tumor and distant metastases is not performed, and another treatment method is selected. If the distant metastases are unresectable but the primary tumor is resectable, the indication for the resection of the primary tumor is determined, based on the clinical symptoms of the primary tumor and the impact on the prognosis.
NCCN guidelines Version 4.2020 (11)	The recommended surgical procedure for resectable colon cancer is an en bloc resection and adequate lymphadenectomy. Adequate pathologic assessment of the resected lymph nodes is important with a goal of evaluating at least 12 nodes. Patients with resectable T4b tumors or with bulky nodal disease may be treated with neoadjuvant systemic therapy prior to colectomy.	Patients with metastatic disease in the liver or lung should be considered for surgical resection if they are candidates for surgery and if all original sites of disease are amenable to resection (R0) and/or ablation. Six months of perioperative systemic therapy should be administered to patients with synchronous or metachronous resectable metastatic disease. When a response to chemotherapy would likely convert a patient from an unresectable to a resectable state (i.e., conversion therapy), this therapy should be initiated.
ESMO consensus guidelines (12,13)	The resection should include a segment of colon of at least 5 cm on either side of the tumor. At least 12 lymph nodes should be resected when feasible. En bloc resection of adjacent organ-invaded portions must be car-ried out in case of pT4b.	In patients with clearly resectable disease and favorable prognostic criteria, perioperative treatment may not be necessary and upfront resection is justi-fied. In patients with technically resectable disease where the prognosis is unclear or probably unfavorable, perioperative combination chemotherapy should be administered. In potentially resectable patients (if conversion is the goal), a regimen leading to high response rates and/or a large tumor size reduction is recommended.

ESMO, European Society for Medical Oncology; NCCN, National Comprehensive Cancer Network.