Clinicopathological characteristics and prognosis of patients with mucious adenocarcinoma originating from the left colon, right colon, or rectum: A nationwide retrospective study in China

BACKGROUND The clinicopathological and prognostic features of colorectal cancers (CRC) originating from different locations differ greatly. However, the impact of tumour location on the clinicopathological features and prognosis of patients with colorectal mucinous adenocarcinoma (MAC) remains underexplored. Materials and Methods The clinicopathological data of CRC patients who underwent curative surgery and were pathologically diagnosed with MAC across 23 hospitals in China from 2016 to 2021 were collected. Data from MAC patients in the Surveillance, Epidemiology, and End Results (SEER) database were also collected. The study was approved by the Institutional Review Board of the First Affiliated Hospital of Shandong First Medical University & Shandong Provincial Qianfoshan Hospital [Approval No.YXLL-KY-2024(116)]. Chi-square analysis, Fisher's exact test, or Kruskal-Wallis ANOVA was used to assess differences in categorical variables where appropriate. Kaplan-Meier curves were generated to assess survival, which was compared via log-rank tests. Univariable and multivariable survival analyses with Cox regression models were conducted to identify prognostic factors. RESULTS A total of 5,763 patients from the SEER cohort and 2,439 patients from the Chinese cohort met the eligibility criteria for inclusion in this study. The SEER cohort comprised 3,827 (66.4%) patients whose disease originated from the right-sided colon (RS), 1,225 (21.2%) from the left-sided colon (LS), and 711 (12.4%) from the rectum (RC). In the Chinese cohort, 993 (40.7%) patients originated from RS, 526 (21.6%) from LS, and 920 (37.7%) from RC. In the SEER cohort, compared with the RS group and LS group, the RC group was significantly associated with aggressive histologic features, including N2 stage (20.8% vs. 15.8% vs. 15.4%, respectively, p  < 0.05) and TNM stage III disease (44.9% vs. 39.8% vs. 37.7%, respectively, p  < 0.05). Compared with the RS group, the LS group was significantly associated with aggressive histologic features, including perineural invasion (25.7% vs. 19.8%, p  = 0.009), N2 stage (21.5% vs. 13.8%, p  < 0.001), and TNM stage III disease (52.1% vs. 40.8%, p  < 0.001), in the Chinese cohort. In addition, compared with the LS group, the RC group had a worse N2 stage (29.5% vs. 21.5%, p  < 0.001) and TNM stage III disease (62.2% vs. 52.1%, p  < 0.001). In the SEER cohort, the 3-year OS of patients in the RC group was significantly lower than that of patients in the RS group and the LS group (61.2% vs. 66.6% vs. 64.7%, p  = 0.04), and compared with the RS, the RC was identified as an independent predictor for 3-year OS (HR 0.802, 95% CI 0.704–0.915, p  = 0.001). No significant differences were observed in OS (85.3% vs. 88.7% vs. 90.7%, p  = 0.061) or DFS (81.5% vs. 84.2% vs. 87.5%, p  = 0.06) among the 3 groups in the Chinese cohort. CONCLUSION This nationwide multicentre retrospective study demonstrated that the clinicopathological features and prognoses of MAC patients differ between patients in Western countries and those in China. In addition, MACs originating from different tumour locations present divergent clinicopathological features and prognostic consequences. These findings provide new evidence for further exploration of the features of MAC, and the tumour location should receive increased attention in the clinical study and treatment of MAC.