Extended procedure has no oncological benefits over segmental resection in the treatment of non-metastatic splenic flexure colon cancer, a population-based cohort study and a single center's decade-long experience.

To compare the oncological survival outcome between extended resections (ER) and segmental resection (SR) for non-metastatic splenic flexure tumors. A total of 10,063 splenic flexure colon cancers patients who underwent ER (n = 5546) or SR (n = 4517) from 2010 to 2018 were included from the Surveillance, Epidemiology, and End Results (SEER)-registered database. Additionally, we included 135 patients from our center who underwent ER (n = 54) or SR (n = 81) between 2011 and 2021. Survival rates were compared between groups. To reduce the inherent bias of retrospective studies, propensity score matching (PSM) analysis was performed. In the SEER database, patients in the ER group exhibited higher pT stage, pN stage, larger tumor size, and elevated rates of CEA level, perineural invasion, and tumor deposits compared to those in the SR group (each P < 0.05). The 5-year cancer-specific survival (CSS) rate was slightly lower in the ER group than in the SR group (79.2% vs. 81.6%, P = 0.002), while the 5-year overall survival (OS) rates were comparable between the two groups (66.2% vs. 66.9%, P = 0.513). After performing PSM, both the 5-year CSS and 5-year OS rates were comparable between the ER and SR groups (5-year CSS: 84.9% vs. 83.0%, P = 0.577; 5-year OS: 70.6% vs. 66.0%, P = 0.415). These findings were consistent in the subgroup analysis that included only patients with stage III disease or tumor size ≥ 7 cm. Furthermore, although the number of harvested lymph nodes was higher in the ER group compared to the SR group (14.4 vs. 12.7, P < 0.001), the number of invaded lymph nodes remained similar between the two groups (0.5 vs. 0.5, P = 0.90). Similarly, our center's data revealed comparable 3-year OS and 3-year disease-free survival (DFS) rates between the two groups. ER have no significant oncological benefits over SR in the treatment of non-metastatic splenic flexure colon cancer, even for locally advanced cases.