The goal of this observational study is to investigate the efficacy and safety of a modified D3 lymphadenectomy approach compared to Complete Mesocolic Excision (CME) in patients with right-sided colon cancer. The main question it aims to answer is:

Does a modified D3 approach improve disease-free survival (DFS) in patients with Stage I-III right-sided colon cancer who undergo right-sided colectomy, without increasing surgical complications compared to CME?

Patients with right-sided colon cancer, Stage I-III, who undergo either modified D3 lymphadenectomy or CME as part of their standard treatment, will have their DFS, complications, bleeding volume, number of lymph nodes harvested, and stage distribution compared over a follow-up period. This study ultimately aims to determine the optimal surgical approach for maximizing oncologic outcomes in right-sided colon cancer.

This observational, population-based, cohort study was conducted following the Strengthening the Reporting of Observational Studies in Epidemiology (STROBE) guidelines. Approval was obtained from the institutional review board (IRB) of the primary institution and the ethics committees of each participating institution in the Republic of Korea. Given that the study utilized anonymized data retrospectively, the need for informed consent was waived.

The study aimed to evaluate the efficacy and safety of modified D3 lymphadenectomy compared to Complete Mesocolic Excision (CME) in patients with right-sided colon cancer. Patients with right-sided colon cancer who underwent laparoscopic or robotic right hemicolectomy from 2013 to 2020 were included. Patients were classified into those who received modified D3 lymphadenectomy or CME, and the study assessed disease-free survival (DFS), surgical complications, bleeding volume, lymph node yield, and stage distribution.

Data collection was carried out at multiple tertiary medical centers across the Republic of Korea, ensuring a broad representation of patient demographics and clinical practices. The participating institutions included Asan Medical Center, Korea University Anam Hospital, Severance Hospital, and Kyungpook National University Chilgok Hospital. These centers vary in location and size, enhancing the study's generalizability within the context of right-sided colon cancer management in Korea.

Inclusion Criteria:

• Patients who underwent laparoscopic or robotic right hemicolectomy from 2013 to 2020
• Patients who received curative right hemicolectomy with lymphadenectomy

Exclusion Criteria:

• Familial adenomatous polyposis (FAP)
• Hereditary non-polyposis colon cancer (HNPCC)
• Patients with inflammatory bowel disease
• Patients with synchronous malignancies in other organs
• Patients with non-adenocarcinoma histology of colon cancer

The study included patients who underwent laparoscopic or robotic right hemicolectomy from 2013 to 2020 at four institutions: Asan Medical Center, Kyungpook National University Chilgok Hospital, Korea University Anam Hospital, and Yonsei University Severance Hospital.